Decay Rates
James R. Hofmann
(very) different conditions in order for the rate involved to be
different, but it probably will get a lot of publicity.
http://www.answersingenesis.org/docs2001/0321acc_beta_decay.asp
Jim Hofmann
http://nsmserver2.fullerton.edu/departments/chemistry/evolution_creation/web/
ReidRover
occuring in "natural" conditions, and i only know elementary physics..Again
they have to guess "what God did" without any evience whatsoever. silly. Usual
creationist guff..they take something performed in a lab ,once , one specific
isotope, and extrapolate it out to regular universal conditions..just doesnt
work..its all "if" God did..useless as science..but makes a nice stroy.
Tracy P. Hamilton
"James R. Hofmann" <jhof...@fullerton.edu> wrote in message
news:3ABB8556...@fullerton.edu...
> Any comments on this AIG article on altered decay rates? It postulates
> (very) different conditions in order for the rate involved to be
> different, but it probably will get a lot of publicity.
Kind of like: "If pigs had wings they could fly".
The dunderheads don't realize that radiodating does not date the
age of the atoms involved, but the age of the rock, and the rock will not
form under conditions where a plasma ionizes all the electrons
off of atoms.
Or if they do realize this, they are being dishonest in making the
"criticism" in the first place.
> http://www.answersingenesis.org/docs2001/0321acc_beta_decay.asp
Tracy P. Hamilton
Adam Marczyk
news:99ga8v$ek1$1...@SonOfMaze.dpo.uab.edu...
>
> "James R. Hofmann" <jhof...@fullerton.edu> wrote in message
> news:3ABB8556...@fullerton.edu...
> > Any comments on this AIG article on altered decay rates? It postulates
> > (very) different conditions in order for the rate involved to be
> > different, but it probably will get a lot of publicity.
>
> Kind of like: "If pigs had wings they could fly".
>
> The dunderheads don't realize that radiodating does not date the
> age of the atoms involved, but the age of the rock, and the rock will not
> form under conditions where a plasma ionizes all the electrons
> off of atoms.
>
> Or if they do realize this, they are being dishonest in making the
> "criticism" in the first place.
It really is amazing watching them bend over backwards to discredit
radiometric dating. Ironically, the only way they can prove their creation
is to make their God a deceptive liar.
Also, I'm thinking, wouldn't it be rather obvious, geologically speaking, if
the rocks in question formed from cooling plasma?
--
When I am dreaming,
I don't know if I'm truly asleep, or if I'm awake.
When I get up,
I don't know if I'm truly awake, or if I'm still dreaming...
--Forest for the Trees, "Dream"
To send e-mail, change "excite" to "hotmail"
Paul J Gans
> Tracy P. Hamilton <che...@uabdpo.dpo.uab.edu> wrote in message
> news:99ga8v$ek1$1...@SonOfMaze.dpo.uab.edu...
>>
>> "James R. Hofmann" <jhof...@fullerton.edu> wrote in message
>> news:3ABB8556...@fullerton.edu...
>> > Any comments on this AIG article on altered decay rates? It postulates
>> > (very) different conditions in order for the rate involved to be
>> > different, but it probably will get a lot of publicity.
>>
>> Kind of like: "If pigs had wings they could fly".
>>
>> The dunderheads don't realize that radiodating does not date the
>> age of the atoms involved, but the age of the rock, and the rock will not
>> form under conditions where a plasma ionizes all the electrons
>> off of atoms.
>>
>> Or if they do realize this, they are being dishonest in making the
>> "criticism" in the first place.
> It really is amazing watching them bend over backwards to discredit
> radiometric dating. Ironically, the only way they can prove their creation
> is to make their God a deceptive liar.
> Also, I'm thinking, wouldn't it be rather obvious, geologically speaking, if
> the rocks in question formed from cooling plasma?
I don't know. I've never seen cooled plasma.
---- Paul J. Gans
Alan Morgan
James R. Hofmann <jhof...@fullerton.edu> wrote:
>Any comments on this AIG article on altered decay rates? It postulates
>(very) different conditions in order for the rate involved to be
>different, but it probably will get a lot of publicity.
It's quite an interesting result. Of course, it just proves that science
is on top of things yet again. We have a theory about atomic decay, made
a prediction based on that theory, and verified that prediction.
Would that creationists could do the same thing.
Alan
Adam Marczyk
news:%5Pu6.47$181...@typhoon.nyu.edu...
Well, I imagine a rock that started out as a plasma cloud and then
solidified (how? did God just add electrons or what?) probably wouldn't look
much like a standard igneous or metamorphic rock.
David Ewan Kahana
It's good for a couple of yucks.
Ionize all the atoms in a rock and beta decay rates will change.
Meanwhile the rock flashes into incandescent gas and spreads
itself to the four corners of the earth. Soon enough it cools and
resolves itself into a microscopic dew. Collect this stuff and I
warrant it will function better for these authors than whatever
presently fills their heads, if indeed their skulls have ever been
found to contain anything at all.
Very different conditions, indeed: let them tell it to the plasma
beings!
cheers,
- dave k.
Dave Oldridge
<99ga8v$ek1$1...@SonOfMaze.dpo.uab.edu>:
>
>"James R. Hofmann" <jhof...@fullerton.edu> wrote in message
>news:3ABB8556...@fullerton.edu...
>> Any comments on this AIG article on altered decay rates? It postulates
>> (very) different conditions in order for the rate involved to be
>> different, but it probably will get a lot of publicity.
>
>Kind of like: "If pigs had wings they could fly".
>
>The dunderheads don't realize that radiodating does not date the
>age of the atoms involved, but the age of the rock, and the rock will not
>form under conditions where a plasma ionizes all the electrons
>off of atoms.
>
>Or if they do realize this, they are being dishonest in making the
>"criticism" in the first place.
They are also being dishonest if they do not know and are claiming the
expertise TO know.
--
Dave Oldridge
ICQ 1800667
=============================================================================
=================
Paradoxically, nearly all real events are highly improbable
--me, 2000AD
Dave Oldridge
<3ABB8556...@fullerton.edu>:
>http://www.answersingenesis.org/docs2001/0321acc_beta_decay.asp
This was interesting, but hardly relevant, since MOST radiometric methods
involve K-capture or alpha decay neither of which have been shown to be
affected. Indeed, if heating to a plasma accelerates beta decay, one might
ask if anyone has observed a corresponding DEcelleration of K-capture, which
depends on finding an electron in a shell.
Mind you, heating any rock to a plasma state would reset most geochemical
clocks anyway! What we are trying to measure is how long since the crystals
formed.
Robert Carroll
Sounds like a vampire's martini.
Bob
>
> ---- Paul J. Gans
>
Robert Carroll
would provide a strong electromagnetic barrier to a beta particle being
ejected from the nucleus. If this were true, K-electrons (and other low
energy electrons in multi-electron atoms) would have much the same barrier
to being excited to higher energy levels, making it much more difficult to
achieve that plasma that Woodmorappe referred to. The reference to nuclear
particles "crashing through" a potential barrier serves to illuminate the
crudity of his understanding of tunneling. It is a thoroughly dishonest
piece of work. Hey, Woody, at what temperatures do these plasmas exist? At
what temperatures do even molten rocks exist? How about solid rocks?
Bob
>
>
>
Paul J Gans
Of course they can. They predict that the Bible is right and
lo and behold, it IS!
---- Paul J. Gans
Paul J Gans
> che...@uabdpo.dpo.uab.edu (Tracy P. Hamilton) wrote in
> <99ga8v$ek1$1...@SonOfMaze.dpo.uab.edu>:
>>
>>"James R. Hofmann" <jhof...@fullerton.edu> wrote in message
>>news:3ABB8556...@fullerton.edu...
>>> Any comments on this AIG article on altered decay rates? It postulates
>>> (very) different conditions in order for the rate involved to be
>>> different, but it probably will get a lot of publicity.
>>
>>Kind of like: "If pigs had wings they could fly".
>>
>>The dunderheads don't realize that radiodating does not date the
>>age of the atoms involved, but the age of the rock, and the rock will not
>>form under conditions where a plasma ionizes all the electrons
>>off of atoms.
>>
>>Or if they do realize this, they are being dishonest in making the
>>"criticism" in the first place.
> They are also being dishonest if they do not know and are claiming the
> expertise TO know.
If what we know of nuclear theory is all wrong, then
not only do nuclear power reactors not work but nuclear
weapons are a fraud.
----- Paul J. Gans
David Jensen
dold...@istar.ca (Dave Oldridge) wrote in
<906DCCA96doldr...@154.11.89.178>:
>jhof...@fullerton.edu (James R. Hofmann) wrote in
><3ABB8556...@fullerton.edu>:
>
>>http://www.answersingenesis.org/docs2001/0321acc_beta_decay.asp
>
>This was interesting, but hardly relevant, since MOST radiometric methods
>involve K-capture or alpha decay neither of which have been shown to be
>affected. Indeed, if heating to a plasma accelerates beta decay, one might
>ask if anyone has observed a corresponding DEcelleration of K-capture, which
>depends on finding an electron in a shell.
>
>Mind you, heating any rock to a plasma state would reset most geochemical
>clocks anyway! What we are trying to measure is how long since the crystals
>formed.
It may be that they think the pre-Flood folks were living on those
plasma rocks.
Stephen F. Schaffner
On the contrary, pretty much everything you see is cooled plasma.
--
Steve Schaffner s...@genome.wi.mit.edu
SLAC and I have a deal: they don't || Immediate assurance is an excellent sign
pay me, and I don't speak for them. || of probable lack of insight into the
|| topic. Josiah Royce
Marty Fouts
Huh. And I thought it was all photons.
Marty
Dave Oldridge
<fl9obto2nnji7m050...@4ax.com>:
That would explain why we don't find a layer of dead bones all at one place
in the geology. :-(
Paul J Gans
Now that's an interesting question. I assume that back in the
Big Bang days there was (or soon would be) much plasma. But the
first thing that plasma seems to do on cooling down is to stop
being a plasma. *That* stuff, I readily admit, can indeed
condense.
---- Paul J. Gans
Steve Carlip
> "James R. Hofmann" wrote:
>> Any comments on this AIG article on altered decay rates? It postulates
>> (very) different conditions in order for the rate involved to be
>> different, but it probably will get a lot of publicity.
> It's good for a couple of yucks.
All else aside, it's hard to take too seriously an article that talks about
``beta (negatron) decay.'' This raises an interesting dating issue, though:
what age are the books from which Woodmorappe learned (or failed to
learn) physics from? I.e., when is the last time the word ``negatron''
was used in a physics book or paper?
(One data point: Bohm's 1951 book on quantum mechanics discusses
beta decay and electrons, not ``negatrons.'')
Steve Carlip
WickedDyno
<sjca...@ucdavis.edu> wrote:
Aren't those the guys that Sailor Moon fights? Oh, wait, that's
Negaverse. Nevermind.
--
| Andrew Glasgow <amg39(at)cornell.edu> |
| SCSI is *NOT* magic. There are *fundamental technical |
| reasons* why it is necessary to sacrifice a young goat |
| to your SCSI chain now and then. -- John Woods |
Karl
says...
> Any comments on this AIG article on altered decay rates? It postulates
> (very) different conditions in order for the rate involved to be
> different, but it probably will get a lot of publicity.
>
> http://www.answersingenesis.org/docs2001/0321acc_beta_decay.asp
>
>
> Jim Hofmann
If atoms were first created in fully-ionized states, accounting for
accelerated decay rates, this leads to a couple of questions:
1) Can the observed isotope ratios in nature be accounted for, given
observed beta(b) rates? I imagine, given that all elements need not have
been created at the same instant, and there may have been differing
initial amounts created, it should be possible to fit a lot of the
observations to this hypothesis.
2) This hypothesis calls for all the decay of beta-decaying nuclides to
have occurred before they were incorporated into minerals. I'd be
curious to know how they account for consistent isochron measurements in
mineral samples. And come to think of it, the bulk of the decay of K-40
must have occurred before the atoms were ever incorporated into matter.
Why do we find minerals with significant amounts of Ar-40 trapped in
their crystal matrices?
3) When we examine natural decay series, we often find beta-decaying
daughter nuclides in "secular equilibrium" with alpha-decaying parent
nuclides. "Secular equilibrium" is the case where a short-lived daughter
product is being continuously replenished by the decay of the parent
nuclide. Thus, a beta emitter with a relatively short half-life, less
than, say, a hundred million years, will be found in nature if it's a
daughter (or grand-daughter or great grand-daughter....) of something
with a half-life of billions of years.
Why do we find relatively long-lived (compared to us, and particularly on
the order of millions of years) in secular equilibrium with **anything**?
There should not have been enought time for such an equilibrium to be
established.
That should do for a start.
...........Karl Lembke
PS This is a cute article. I'm going to add a link and this rebuttal to
my website.
wf...@ptd.net
>In article <3ABB8556...@fullerton.edu>, jhof...@fullerton.edu
>says...
>> Any comments on this AIG article on altered decay rates? It postulates
>> (very) different conditions in order for the rate involved to be
>> different, but it probably will get a lot of publicity.
>>
>> http://www.answersingenesis.org/docs2001/0321acc_beta_decay.asp
>>
>>
>> Jim Hofmann
>
>If atoms were first created in fully-ionized states, accounting for
>accelerated decay rates, this leads to a couple of questions:
>
>1) Can the observed isotope ratios in nature be accounted for, given
>observed beta(b) rates? I imagine, given that all elements need not have
>been created at the same instant, and there may have been differing
>initial amounts created, it should be possible to fit a lot of the
>observations to this hypothesis.
>
basically the process calls for so much energy to be put into atoms to
ionize them, that the universe would never form. completely ionized
atoms heavier than, say, He, have ALOT of energy. what it requires is
that god decides to lie to us, make up alot of special conditions
never seen outside of the interior of stars, place these conditions on
the face of the earth, then expose living organisms to the energy.
pretty neat process! of course, creationists falsify their own
arguments when they argue like this, but far be it from creationists
to ever argue SCIENTIFICALLY when magic will do.
Sverker Johansson
> "James R. Hofmann" <jhof...@fullerton.edu> wrote in message
> news:3ABB8556...@fullerton.edu...
> > Any comments on this AIG article on altered decay rates? It postulates
> > (very) different conditions in order for the rate involved to be
> > different, but it probably will get a lot of publicity.
> >
> > http://www.answersingenesis.org/docs2001/0321acc_beta_decay.asp
> >
> >
> > Jim Hofmann
> >
> http://nsmserver2.fullerton.edu/departments/chemistry/evolution_creation/web
> /
> >
> >
> The argument seems to be that the electron cloud surrounding a nucleus
> would provide a strong electromagnetic barrier to a beta particle being
> ejected from the nucleus.
Not quite. The nucleus itself has an electric field which holds on
to electrons around it. With the full complement of normal electrons,
there is no room for the new beta-decay electron near the nucleus,
so the decay process has to supply enough energy to boost the electron
out from the field of the nucleus. If there are no electrons in the
K shell, then the decay process only needs enough energy to get an
electron from the nucleus into the K shell, which can be significantly
less.
> If this were true, K-electrons (and other low
> energy electrons in multi-electron atoms) would have much the same barrier
> to being excited to higher energy levels,
They do.
> making it much more difficult to
> achieve that plasma that Woodmorappe referred to.
That's why we don't have Rhenium plasmas at any Earthly conditions.
> The reference to nuclear
> particles "crashing through" a potential barrier serves to illuminate the
> crudity of his understanding of tunneling. It is a thoroughly dishonest
> piece of work.
Yes, it's dishonest, but not because the physics in it is wrong.
The process is well known to operate inside stars.
It's the application to Earthly rocks that's dishonest.
> Hey, Woody, at what temperatures do these plasmas exist? At
> what temperatures do even molten rocks exist? How about solid rocks?
--
Best regards, HLK, Physics
Sverker Johansson U of Jonkoping
----------------------------------------------
Definitions:
Micro-evolution: evolution for which the evidence is so
overwhelming that even the ICR can't deny it.
Macro-evolution: evolution which is only proven beyond
reasonable doubt, not beyond unreasonable doubt.
Sverker Johansson
>
> In article <3ABB8556...@fullerton.edu>, jhof...@fullerton.edu
> says...
> > Any comments on this AIG article on altered decay rates? It postulates
> > (very) different conditions in order for the rate involved to be
> > different, but it probably will get a lot of publicity.
> >
> > http://www.answersingenesis.org/docs2001/0321acc_beta_decay.asp
> >
> >
> > Jim Hofmann
>
> If atoms were first created in fully-ionized states, accounting for
> accelerated decay rates, this leads to a couple of questions:
>
> 1) Can the observed isotope ratios in nature be accounted for, given
> observed beta(b) rates?
Within the uncertainties, yes. Notably, the only isotopes found
in appreciable amounts in nature are those with either a long
(millions of years) half-life under current conditions, or with
a well-understood current production process (e.g. C14).
> I imagine, given that all elements need not have
> been created at the same instant, and there may have been differing
> initial amounts created, it should be possible to fit a lot of the
> observations to this hypothesis.
It's a stronger constraint for some elements, where we better
understand the production process. Uranium, for example, can be
used to constrain the age of its formation. By some odd coincidence,
this comes out very close to the age of Big Bang.
> 2) This hypothesis calls for all the decay of beta-decaying nuclides to
> have occurred before they were incorporated into minerals. I'd be
> curious to know how they account for consistent isochron measurements in
> mineral samples. And come to think of it, the bulk of the decay of K-40
> must have occurred before the atoms were ever incorporated into matter.
> Why do we find minerals with significant amounts of Ar-40 trapped in
> their crystal matrices?
>
> 3) When we examine natural decay series, we often find beta-decaying
> daughter nuclides in "secular equilibrium" with alpha-decaying parent
> nuclides. "Secular equilibrium" is the case where a short-lived daughter
> product is being continuously replenished by the decay of the parent
> nuclide. Thus, a beta emitter with a relatively short half-life, less
> than, say, a hundred million years, will be found in nature if it's a
> daughter (or grand-daughter or great grand-daughter....) of something
> with a half-life of billions of years.
>
> Why do we find relatively long-lived (compared to us, and particularly on
> the order of millions of years) in secular equilibrium with **anything**?
> There should not have been enought time for such an equilibrium to be
> established.
God created just the right amount to fool us heathens, so that he has
an excuse to send us to Hell, where we will stay until Hell freezes over
due to nuclear decay heat.
Walter Bushell
Not at all. The Sun by itself sensibly out masses everything else we can
see. And that does not take into account the other stars. So
practically almost everything we can see is hot plasma.
Robert Carroll
"Sverker Johansson" <l...@hlk.no.hj.spam.se> wrote in message
news:3ABF147C...@hlk.no.hj.spam.se...
> Robert Carroll wrote:
> > "James R. Hofmann" <jhof...@fullerton.edu> wrote in message
> > news:3ABB8556...@fullerton.edu...
> > > Any comments on this AIG article on altered decay rates? It postulates
> > > (very) different conditions in order for the rate involved to be
> > > different, but it probably will get a lot of publicity.
> > >
> > > http://www.answersingenesis.org/docs2001/0321acc_beta_decay.asp
> > >
> > >
> > > Jim Hofmann
> > >
> >
http://nsmserver2.fullerton.edu/departments/chemistry/evolution_creation/web
> > /
> > >
> > >
> > The argument seems to be that the electron cloud surrounding a nucleus
> > would provide a strong electromagnetic barrier to a beta particle being
> > ejected from the nucleus.
>
> Not quite. The nucleus itself has an electric field which holds on
> to electrons around it. With the full complement of normal electrons,
> there is no room for the new beta-decay electron near the nucleus,
> so the decay process has to supply enough energy to boost the electron
> out from the field of the nucleus. If there are no electrons in the
> K shell, then the decay process only needs enough energy to get an
> electron from the nucleus into the K shell, which can be significantly
> less.
Right. I was overlooking nuclear charge. This seems to be the inverse of
K-electron capture. I'm surprised at the large changes in decay rate,
though.
Bob
Stephen F. Schaffner
Sverker Johansson
>
> In article <1eqvn6y.1cchnlopecx8N%pr...@panix.com>,
> Walter Bushell <pr...@panix.com> wrote:
> >Stephen F. Schaffner <ssc...@flora03.SLAC.Stanford.EDU> wrote:
>
> >> On the contrary, pretty much everything you see is cooled plasma.
> >
> >Not at all. The Sun by itself sensibly out masses everything else we can
> >see. And that does not take into account the other stars. So
> >practically almost everything we can see is hot plasma.
>
> Yeah, but it's still cooler than it used to be.
True, sort of. But it's also truw that it's hotter than
it used to be. Until a short while after the BB, the stuff
was hotter than the center of the sun today. For a while longer,
it was hotter than the surface of the sun today. After that,
the bulk of the sun's matter spent some billions of years at
ambient temperatures dropping towards a few Kelvin. Some small
fraction did time as hot plasma inside other stars.
But right now the hot plasma in the sun is gradually
getting hotter, not cooling down, as the sun slowly
grows in luminosity during its sejour on the
main sequence.
Stephen F. Schaffner
Sverker Johansson <l...@hlk.no.hj.spam.se> wrote:
>"Stephen F. Schaffner" wrote:
>>
>> In article <1eqvn6y.1cchnlopecx8N%pr...@panix.com>,
>> Walter Bushell <pr...@panix.com> wrote:
>> >Stephen F. Schaffner <ssc...@flora03.SLAC.Stanford.EDU> wrote:
>>
>> >> On the contrary, pretty much everything you see is cooled plasma.
>> >
>> >Not at all. The Sun by itself sensibly out masses everything else we can
>> >see. And that does not take into account the other stars. So
>> >practically almost everything we can see is hot plasma.
>>
>> Yeah, but it's still cooler than it used to be.
>
>True, sort of. But it's also truw that it's hotter than
>it used to be. Until a short while after the BB, the stuff
>was hotter than the center of the sun today. For a while longer,
>it was hotter than the surface of the sun today. After that,
>the bulk of the sun's matter spent some billions of years at
>ambient temperatures dropping towards a few Kelvin. Some small
>fraction did time as hot plasma inside other stars.
>
>But right now the hot plasma in the sun is gradually
>getting hotter, not cooling down, as the sun slowly
>grows in luminosity during its sejour on the
>main sequence.
I know.
I actually had a point buried somewhere under my comment: what
might have happened to decay rates in a plasma have nothing
whatever to do with the radio-dating of objects on Earth.
David Ewan Kahana
I agree completely that it's impossible to take the article seriously.
You raise an interesting question though, and I am not completely sure of the
answer. The term positron for the positively charged anti-particle of the
electron has definitely won out by now, but I couldn't tell you precisely
when that happened.
In the early days of learning about the theory of beta decay (let's say, for
the sake of argument, the years from 1945-1960, when the really crucial
experiments began to be feasible), it seems to have been pretty common to
refer to electrons, when talking about either the positively charged or the
negatively charged version. People seem to have referred to negatrons or
positrons explicitly, when they needed to distinguish the charge conjugates.
For example, I have a copy of Preston's `Physics of the Nucleus' (copyright
1962, second printing in 1963, but the author says the text was mostly
written in about 1957.) He writes the following in his chapter on the theory
of beta decay:
"In this chapter, but not elsewhere, we shall use the term electron to
include particles of both charges, using the terms positron and negatron when
we wish to distinguish between them."
In the next sentence he elaborates:
"Similarly the word *meson* is a generic term for both \mu^+ and \mu^-."
[emphasis added]
Clearly there's been quite a bit of flux in terminology since those days. By
now we generally don't speak about mu-mesons anymore, the muon having been
identified as a second class of lepton, despite the coincidence that it has a
mass on the same order as that of the pi-meson.
Are you sure that Bohm is not discussing beta decay generically when he uses
`electron'? Does he discuss positron emission too? Does he ever use the word
`negatron' at all? If the answers are yes and no, then we know that among at
least one group of theoreticians electron and positron were already
well established for the electron and its anti-particle.
It could be then, that Preston was a bit behind the times or conservative
about terminology.
However, his understanding of what was then known about the theory of the
weak interactions seems to me to be pretty much impeccable. In any case,
it's for sure that someone who had read Bohm has no excuse for being as
confused about the theory of nuclear beta decay as Woodmorappe is. The answer
to your implicit question is, of course, that Woodmorappe has utterly failed
to learn any physics at all. His discussion clearly confuses beta decay with
alpha decay. The two have completely different mechanisms.
The piece of physics discussed here is actually rather fascinating, though it
is in an important sense a very special phenomenon, and certainly utterly irrelevant
to the radio-dating of terrestrial rocks. I've followed up a little bit
on the question and plan to write a bit more later on.
cheers,
- dave k.
David Ewan Kahana
You're right, this process is in fact very like K-capture, but time-reversed,
and with all of the other atomic electrons removed from the picture.
The argument presented in the article is simply bizarre. Anyone who reads it
for very long does so at the risk of suffering severe brain damage. It
contains confusion at near toxic levels. In my opinion a quite careful effort
has been made here to misdirect the reader, and there is an implicit
assumption that the readers will be unsophisticated.
The factor of 10^9 enhancement of the decay rate in fully stripped 187 Re is
indeed extremely surprising on the face of it. I was surprised to hear of
that myself. But it's important to remember that the decay of 187 Re is not
really a very typical beta decay. More on this later.
The first hint that something quite special is up and that the author is
attempting to mislead you about it, even if you didn't know anything at all
about the physics of beta decay, is provided by Woodmorappe himself, when he
refers to the 163 Dy system, which is stable as a neutral atom, but has been
observed to decay to 163 Ho quite quickly when it is fully stripped. Why
doesn't Woodmorappe point out that this is an incredible enhancement of the
beta decay rate by a factor of infinity? Isn't that a much more spectacular
effect than a mere nine orders of magnitude?
Woodmorappe doesn't want you to think about this question for too long, so he
doesn't make it a central point. He wants you just to believe that *all* beta
decays will be affected in just this way by stripping, and he later suggests that
the variation probably might extend to alpha decays as well. This is why he
first goes so far as to provide a spurious explanation for the broad
phenomenology of beta decay lifetimes.
In the mind of any physicist who has ever calculated a nuclear beta decay, a
partial explanation for the effect would already be forming or would be fully
formed already, by the time that Woodmorappe mentions 163 Dy.
K-electrons, beta decay electrons, and any other electrons which find
themselves deep inside multi-electron atoms do in fact all have a `barrier'
to being excited to higher energy levels. But one doesn't generally talk
about a barrier in this case, because the actual potential for electrons
doesn't have a barrier. It is a purely attractive potential, with close to a
1/r dependence right up to the edge of the nucleus, changing over to an r^2
dependence in the region of constant charge density inside.
Remember that this is a beta decay: it is essentially a weak process
resulting from a zero range interaction. It is very different from an alpha
decay, in which the competition between the long range repulsive Coulomb
forces inside the *nucleus* and the attractive short range strong
interactions produce an actual barrier that an alpha particle must penetrate
in order to escape from the nucleus.
Repeating it once more, all of the electrons feel the attractive Coulomb
force from the nucleus, corrected by screening due to other electrons, and
the repulsion of the other electrons. The Pauli principle operates, so that
an inner electron cannot be excited to any of the occupied levels above it.
All but the very highest levels in a multi-electron atom, in its ground
state, are filled with the maximum possible number of electrons: no more
electrons can be put into these states. To be excited, any electron must be
given energy sufficient to get above the Fermi level in the atom. To within a
few eV, the Fermi level will coincide with the continuum. At least enough
energy must be given to a decay electron then, that it can reach an
unoccupied bound state in the new atom (which has one more unit of positive
charge on its nucleus), otherwise the decay will be energetically
forbidden. In most beta decays, much more than this amount of energy is
available.
Coulomb corrections to the electron wavefunction are always present when
calculating beta decays, but though they are certainly substantial in certain
regions of phase space, they are not generally responsible for such
spectacular effects as are seen here.
But the account Woodmorappe gives of the mechanisms is not to be taken
seriously. One can safely ignore what little he writes about the
details. Here is a choice expository passage in which he beautifully
illustrates his willful ignorance of the subject:
"This acceleration can occur under beta (negatron) decay. During b decay
itself, a neutron changes into a proton, electron and electron-antineutrino,
and the electron is expelled as a negative beta particle (b- - often written
without the negative sign, but sometimes it is necessary to distinguish it from
the rarer positive beta or positron decay b+). Because of the fact that the
protons in the nucleus and the b particles have opposite charges, they attract
each other, and the b- must therefore acquire sufficient kinetic energy to
overcome this attraction in order to escape the nucleus. This has been likened
to a particle having sufficient energy to crash through the walls of a well.2 In
some b- emitters, the successful escape of a b-particle into the continuum is a
relatively infrequent occurrence-hence the inferred long half-life of the
nuclide."
Not to put to fine a point on it, but at this point the discussion is already
complete crap. It is true in all the incidental details, but it is all
essentially irrelevant. After this point the discussion in the article
degenerates even further. Do not even try to learn about beta decay from this
man.
I think his rather clear suggestion, here, is that beta decay electrons are somehow
held inside the nucleus by the Coulomb force, that otherwise they would
easily escape, and that that is the root cause of certain very long
*predicted* and *observed*, rather than `inferred' beta decay lifetimes.
What he says is completely backwards. He pretends that the special case is
the general case, he says nothing useful about the underlying mechanisms, and
he is wrong in all of his conclusions as well as his subsequent
mis-application of the ideas to radioactive dating of rocks.
In the great majority of neutral atom beta decays one can do reasonably well
by ignoring the Coulomb attraction of the nucleus for the decay electron, as
well as the repulsion of the atomic electrons for the decay electron. These
are usually small corrections to the process, because the energy available
from the change of the nuclear state, which always occurs in a weak nuclear
decay, is generally much larger than the change in the atomic binding
energy. Known beta decays have endpoint energies a wide range: but most
typically these fall between a few hundred and several thousands of
keV. `Crashing through the walls of a well,' is just not an issue for the
electrons emitted in beta decays.
The decay electron is almost always simply emitted into the continuum, and
the chance of capture into an atomic bound state is very small. The Pauli
principle forbids the decay electron from being captured into a deeply bound
state of a multi-electron atom, since the inner orbitals generally remain
fully occupied in the daughter atom. This statement is almost always true
despite corrections for non-orthogonality of the atomic wave-functions in the
daughter atom, due to the change of the nuclear charge. Capture into an outer
orbital is generally quite strongly suppressed due to the weak binding of
outer electrons and the small wavefunction overlap with the decay electron.
It might be worth pointing out a few more simple facts about the
phenomenology and the theory of beta decay. Beta decay is in the present
context treatable theoretically as if it resulted from a zero-range,
current-current interaction, which transforms a proton (neutron) bound within
a nucleus into a neutron (proton), with the simultaneous creation or
absorption of an electron (positron) and a neutrino (anti-neutrino). The
naturally occuring nuclear beta decays were very early on shown
experimentally to be directly associated with transitions between discrete
stationary states of the parent and the daughter nucleus, most usually a
transition from the ground state of the parent to the ground state or a low
lying excited state of the daughter.
Depending on the details of the nuclear structure, such a process may or may
not require a large rearrangement of the nuclear state, and may or may not
release a lot of energy. If the only change required in the nuclear state is
a change in the charge state, or equivalently, the z-component of the
isospin, and a readjustment of the nuclear well due to the change in nuclear
Coulomb energy, the transition is generally called super-allowed. Such
transitions are the most favoured possible beta decays, and they typically
have small lifetimes, once one corrects for the basic underlying energy
dependence of weak decays.
This energy dependence, by the way, is very strong. For large enough total
decay energies, the dependence is roughly as (W_0)^5 where W_0 is the
endpoint electron energy.
The premier example of a super-allowed beta decay is of course the decay of
the neutron in free space into the proton, with a lifetime of about 1000
seconds. Superallowed decays fall into a group with the lowest possible (ft)
values. Actually one really discusses log_{10} (ft), where t is the half-life
and f is a theoretical factor which corrects for the widely differing total
energies of nuclear beta decays.
The real explanations for sometimes very long beta decay half-lives which are
predicted by theory and *observed* in nature (not `inferred') in quite a few
naturally occuring, neutral, beta unstable atoms is that these atoms can now
be seen to fall into two general classes. The classes are not mutually
exclusive.
The first class includes those decays where the nuclear matrix element is
large or at least not unusually small, but there is simply not very much
energy available for the decay.
The second class includes cases in which the nuclear matrix element for the
transition is extremely small, though there may or may not be ample energy
available.
The first class includes certain allowed (as opposed to super-allowed)
transitions, as well as some so-called forbidden transitions of various
orders. Allowed transitions are those which can still occur when the spatial
dependence of the electron and neutrino wavefunctions across the nucleus is
ignored. To within about 1 percent, this is actually a good first
approximation in most beta decays. Other transitions for which we must look
to higher orders in the expansion of the wavefunctions are suppressed by
additional factors on the order of 100, and are these are thus called
forbidden transitions. The order of forbiddenness is related to the order in
the expansion of the electron wavefunction in powers of the momentum at which
the first contributions to the decay are obtained.
Selection rules for the allowed decays are Delta-J = 0 with no change of
parity for so-called Fermi or vector transitions, and Delta-J=0,1 with no
change of parity for Gamow-Teller transitions. Transitions with higher
Delta-J or a change of parity are always first or higher order forbidden.
The total energy available for this beta decay which Woodmorappe concentrates
on is tiny. It is the decay of the 5/2+ ground state of neutral 187 Re to the
1/2- ground state of 187 Osmium with an endpoint energy of W_0 = 2.6
keV. This decay is a so-called unique (meaning only one operator in the
expansion connects the two nuclear states) first forbidden transition. The
Delta-J is 2, and there is a change of parity. These factors together account
for the very long lifetime of the neutral atom.
Just above the ground state in 187 Osmium, at only 9.75 keV, lies the 3/2-
first excited state. Decay to this state from 187 Rhenium, if possible, would
still be a first forbidden transition, but because Delta-J is only 1, it is a
non-unique first forbidden transition, which is somewhat more favoured than a
unique one. However decay to this state is not even a possibility in the
neutral system at normal temperatures: it is energetically forbidden.
Now, the critical point to understand here is that in a very large atom, like
Rhenium or Osmium, the total Coulomb binding of the atomic electrons is not
at all a small number. It is especially not a small number in comparison to
the tiny endpoint energy of this particular beta decay. The total electronic
binding is in fact on the order of 400-500 keV. In addition, the binding is
about 20 keV larger in Osmium than it is in Rhenium, due to the extra unit of
nuclear charge. It's not very hard to make rough estimates of these numbers
knowing just a very little about atomic physics.
Furthermore, the binding of a K-electron in these systems is approaching 90
keV in the stripped, hydrogen-like atom, though in the neutral atom it will
be somewhat less due to screening from the second K-electron. So if we apply
our normal intuition about beta decays here to estimate what might happen to
the lifetime of the system when 75 bound atomic electrons have been stripped
away and say confidently, nothing much at all, we will be sunk. The nuclear
energy levels have been shifted relative to each other by a considerable
amount and the energetics of the decay clearly has to be reconsidered.
In the end, the transition to the 3/2- first excited state with a bound
K-electron becomes energetically allowed, and that is the dominant decay mode
for the stripped system. There is much more energy available for the decay:
about 60 keV versus 2 keV in the neutral system, and that, together with the
increased overlap due to the smaller change in J is quite sufficient to
account for 9 orders of magnitude enhancement of the decay rate. Beta decay
into the continuum, interestingly, is not even energetically allowed in the
stripped atom.
So we see that the systems for which this sort of thing is a very important
effect are quite special. To find them, one must comb through hundreds of
known beta decays, and come up with the few that have happen to have small Q
values, which are comparable to the changes in atomic Coulomb binding when
going from stripped or highly ionized atom to neutral atom.
The general rule, however, is approximately this: for the most part, nothing
extremely spectacular will happen to total beta decay rates of most beta
unstable atoms (electron emitters), even if the atoms are totally stripped.
Moreover, because of the nature of quantum mechanics in a coulomb potential,
it will be necessary to nearly completely strip the atoms in most cases, to
be able to see any effect at all. Eliminating a valence electron will simply
not be enough, and that is all that can be achieved at any reasonable
temperature.
It is interesting that Woodmorappe completely omits any discussion in this
article of the case of Potassium 40, which is unstable against positron
emission, K-capture, to Argon 40 and by electron emission to Calcium 40. This
is the relevant system in the well known Potassium-Argon dating
technique. The dominant decay mode for the positron emission here is a third
forbidden Delta-J=4 transition, with a change of parity. The total decay
lifetime of the branch to Argon is about 1.28 billion years. The available
energy is however, much larger, the endpoint being W_0 ~= 1320 keV. The
effect of completely stripping the atoms on the decay rate in this system,
though certainly different from zero, will be far less than it was in
Rhenium.
The same applies to yet another case, and I wonder even more why Woodmorappe
has ignored this one. Consider the odd-odd nucleus 186 Rhenium, which beta
decays by electron emission to the neighboring nucleus 186
Osmium. Considerations of atomic binding energies are very nearly the same as
for the case we just went through in detail. This transition is from the 1-
ground state of Rhenium 186, and has a branch of about 75% to the 0+ ground
state of Osmium 186 (which, being an even-even nucleus, is much more bound
than is Osmium 187). There is also a 23% branch to the first (2+) excited
state of Osmium, as well as smaller branches to two higher excited
states. Both transitions are first forbidden, Delta-J=1, with a parity
change. The endpoint energy of the transition to the 2+ state, however, is
about 930 keV, and that to the ground state is nearer to 1100 keV. Again, we
can expect much more modest effects to occur when the systems are totally
ionized.
I will now conclude with a few remarks on the relevance of this silly and
massively dishonest article to radioactive dating and geological time scales.
I am doing no more than to repeat points that others have made here, but I
have added a couple of numbers, just for fun.
Large atoms as we know'em and like'em, namely at all temperatures important
for questions of rock formation, can be thought of as being essentially
neutral when it comes to calculating their beta decays.
It is these kinds of atoms that make up rocks, whether molten or solid, and
that of course includes the rocks in Woodmorappe's head. One does not
typically find Rhenium atoms in charge states like 75+. It took quite a few
talented people working at a complicated and expensive facility, using an
accelerator like the one at GSI, to produce a useable number of these exotic
objects for their experiment. To see just how absurd the discussion
Woodmorappe gives of the earth's origins actually is, it's worth making a
couple of simple order of magnitude estimates.
First, the gravitational binding energy of the earth can be roughly estimated
from the formula for a uniform sphere:
B = 3/5 G m^2 / r
Taking approximate values r=6500 km, m=6x10^24 kg, and G = 6.67 x 10^-11 m^3
/ kg / s^2, this gives:
B = 2.2 x 10^36 J.
This corresponds to a binding energy per unit mass of:
b = 3.7 x 10^7 J / kg,
or a binding energy fraction (dividing b by c^2) for the earth of:
f (earth) = 4 x 10^-10.
What sort of conditions are required to make 75+ the expected charge state of
Rhenium? Here I am going to play very fast and loose with my estimates. If
the separation energy of the first electron in Rhenium is about 9 eV, and
that of the last is about 90 keV, that suggests a total binding energy of
about 500 KeV for all of the electrons. To separate the last electron we thus
need a temperature at least on the order of 10^9 K, while smaller
temperatures would suffice for ionizing the rest of the outer electrons. We
shall need to approach charge states of 72+, 73+ or more preferrably 74+,
I'ld bet, in order to see very strong effects on the beta decay lifetime. If
the K-shell is completely empty in Osmium, then capture to the L-shell is
energetically allowed, but it is greatly suppressed over K-capture. So
perhaps T = 10^8 K might be sufficient. To approach this kind of temperatures
in the current universe, we shall need to make a descent into the core of a
supergiant star. Or perhaps we could wait around for the shock wave of a
supernova explosion to hit us. So while the result discussed in the article
concerning bound state beta decays of fully ionized Rhenium seems possibly to
be very interesting for astrophysics, it is certainly quite irrelevant for
any estimates of the age of terrestrial rocks.
To make this point a little clearer, if it isn't clear enough already,
consider that the binding energy fraction for the electrons in neutral
Rhenium is by my above estimate on the order of:
f (Rhenium) = (500 x 10^3 eV) / (187 x .938 10^9 eV) = 1.08 x 10^-6
Thus, in the process of raising the entire planet earth to the temperature
necessary to make 75+ the expected charge state for Rhenium so that it could
then quickly decay into Osmium, before the earth cooled, God therefore also
must have made the earth gravitationally unbound. The whole planet would
simply have exploded into a cloud of plasma which would even yet be expanding
into space. A cloud at this temperature, having the mass of the earth, could
never have coalesced to form the earth.
Unless, of course, the hand of God squeezed the plasma back into place, or He
also adjusted the gravitational coupling constant ...
Now, if one is the sort who is happy with that kind of explanation, then why
should one bother vomiting forth a totally botched article on the fascinating
and complex physics of exotic nuclear beta decays, in an effort to make this
religious point? Why wouldn't one simply assert that it's clear that God put
every single atom right into its present place, and that the angels are still
pushing all of the tiny little electrons around in their classical orbits?
That at least would be a much more honest statement of one's actual beliefs.
> >
> > > If this were true, K-electrons (and other low
> > > energy electrons in multi-electron atoms) would have much the same
> barrier
> > > to being excited to higher energy levels,
> >
> > They do.
> >
> > > making it much more difficult to
> > > achieve that plasma that Woodmorappe referred to.
> >
> > That's why we don't have Rhenium plasmas at any Earthly conditions.
> >
> > > The reference to nuclear
> > > particles "crashing through" a potential barrier serves to illuminate
> the
> > > crudity of his understanding of tunneling. It is a thoroughly dishonest
> > > piece of work.
> >
> > Yes, it's dishonest, but not because the physics in it is wrong.
> > The process is well known to operate inside stars.
> > It's the application to Earthly rocks that's dishonest.
> >
Hi Sverker. I agree with everything you've said about the physics, but I
think you're being much too kind here about Woody. (Of course, that's not
very kind at all when you're calling him dishonest.)
He has quoted some correct results of physics, but there isn't very much in
what he himself says about the physics that's correct and neither has he
drawn any really correct conclusions as far as I can tell.
cheers,
- dave k.
Adam Marczyk
David Ewan Kahana <d...@bnl.gov> wrote in message
news:3AC26990...@bnl.gov...
--
When I am dreaming,
I don't know if I'm truly asleep, or if I'm awake.
When I get up,
I don't know if I'm truly awake, or if I'm still dreaming...
--Forest for the Trees, "Dream"
To send e-mail, change "excite" to "hotmail"
Paul J Gans
Thank you for a most informative posting. I appreciate it.
---- Paul J. Gans
Grant Bazan
Karl wrote:
Yes, the relative abundances of almost all known isotopes is well predicted
using standard laboratory beta-decay rates altered to take into account
contributions from populations of nuclei in excited states that have either
lower or higher beta decay rates. These are used in combination with
measured
and theoretically derived neutron capture cross sections to infer the
abundances
of nuclei heavier than Germanium via the named s- & r-processes in
astrophysics.
By the way, the astrophysical sites of these processes have been identified,
and
in one case (s-process) been observed (AGB stars in transition from M-type
to S-type to C-type).
Dr. Grant Bazan
LLNL
Stephen F. Schaffner
Robert Carroll
"Stephen F. Schaffner" <ssc...@flora03.SLAC.Stanford.EDU> wrote in message
news:9a69ff$b97$1...@nntp.Stanford.EDU...
> In article <99tuo1$1e0e$1...@node17.cwnet.frontiernet.net>,
> Adam Marczyk <ebon...@excite.com> wrote:
> >Damn. I nominate for PotM.
>
> Ditto, or second, or whatever.
Right. This is a resource that must be archived. We'll probably be seeing
folks showing up here with the familiar "explain this if you can" posts.
Bob
David Ewan Kahana
[snip]
I hate to answer my own post, especially when people have looked kindly on
it, but what I said in the following paragraph requires a minor erratum:
>It is interesting that Woodmorappe completely omits any discussion in this
>article of the case of Potassium 40, which is unstable against positron
>emission, K-capture, to Argon 40 and by electron emission to Calcium 40. This
>is the relevant system in the well known Potassium-Argon dating
>technique. The dominant decay mode for the positron emission here is a third
>forbidden Delta-J=4 transition, with a change of parity. The total decay
>lifetime of the branch to Argon is about 1.28 billion years. The available
>energy is however, much larger, the endpoint being W_0 ~= 1320 keV. The
>effect of completely stripping the atoms on the decay rate in this system,
>though certainly different from zero, will be far less than it was in
>Rhenium.
I should amend this discussion of the A=40, Argon-Potassium-Calcium system: I
went over it a little too quickly. There are some mistakes in what I said in
the paragraph above, which don't affect any overall conclusions, but which
are actually interesting for evaluating Woodmorappe's article.
The lifetime I quoted here was, of course, the total decay lifetime for the
neutral atom, including all of the decay modes. The branch to 40 Ca actually
accounts for about 89% of the decays. The other 11% of the decays almost all
occur by K-capture to 40 Ar.
The total atomic electron binding in these systems can be estimated from the
values in potassium (Z=19). I estimate that the total binding of the atomic
electrons here is about 15 keV, while the binding of a K-electron in the
stripped atoms is about 5 keV.
The first excited state (0+) of 40 Ca lies well above the ground state at
3352 keV, and it can just be ignored here. The first excited state (3-) of 40
K is quite low lying at about 30 keV, but it too can safely be ignored at
normal temperatures. All the decays thus occur from the ground state of
Potassium 40.
The endpoint energy I quoted, 1320 keV, is that for the dominant decay mode
of the (4-) ground state of neutral 40 K. This mode is actually electron
emission to the (0+) ground state of 40 Ca, not positron emission to the (0+)
ground state of 40 Ar. The difference in the atomic masses of 40 Potassium
and 40 Argon is 1503 keV: so that is the total energy available for the decay
which is of most interest in the dating technique.
Positron emission to the ground state is energetically allowed and does
occur, but as it turns out, only rarely. K-capture to the ground state
dominates positron emission to the ground state, and both of these are
dominated by decays to the first excited state (2+) which is at 1460 keV.
The endpoint energy for positron emission is W_0=489 keV, quite a bit less
than what I said. But it is not enough less that we have to worry about
energy shifts due to binding of atomic electrons in going to the stripped
system: these are, both relatively and absolutely speaking, far smaller than
in the Rhenium-Osmium case.
On the Argon side of the diagram, I've pointed out there are two states to
consider. There is the 0+ ground state, to which the Q-value in the neutral
system is 1503 keV, and there is also the 2+ first excited state, which lies
1460 keV above the ground state, so with a Q-value of 43 keV. The transition
to the 2+ first excited state has a smaller Delta-J and is only first
forbidden. Even though the Q value is small, K-capture to this state is the
dominant mode for producing Argon-40. Positron emission is energetically
forbidden in the transition to the first excited state, and all decays to the
ground state are strongly suppressed by the nuclear matrix elements despite
the larger available energy. The first excited state then decays to the
ground state by emitting a 1460 keV photon (it's an E2 transition.) There
can also be various associated X-rays, internal conversions, and Auger
electrons. I won't get into discussing all of these subtleties.
Considering these facts, we can see that the fully stripped system is naively
expected to have the same decay lifetime, to within about 10%. The 10% change
comes about because fully stripped Potassium has no K-electrons. K-capture is
therefore not a possible decay mode for an isolated fully stripped Potassium
atom. The widths for positron and electron emission into the continuum are
not much affected, but K-capture is gone. If the atom still had one bound
electron
though, then the mode would still be allowed.
The conclusion would appear to be that fully stripped, isolated Potassium 40
hardly ever decays to Argon 40 at all. The decay rate should go essentially
to zero, exactly the opposite of the behaviour which Woodmorappe trumpets
proudly in the case of Rhenium.
Of course, under realistic and imaginable conditions, where Potassium or
Rhenium could actually be fully stripped, namely in very hot neutral plasmas,
we should have to also consider other reactions, such as capture of continuum
electrons, as well as possibly contributions from additional low lying
excited states of the various nuclei. This statement is valid for Rhenium 187
as well.
If these channels are opened up, it will likely make the total changes in
production rates, at least for Potassium/Argon, rather smaller than what is
naively predicted, or observed for the isolated atoms.
But these are problems of nucleosynthesis, not of radioactive dating, and
that is perhaps a good place to end my erratum.
cheers,
- dave k.
[snip]
Adam Marczyk
news:3ACA93FD...@sprintmail.com...
Figures. Now what am I going to do if you win PotM? ;)
--
James R. Hofmann
Thanks,
Jim Hofmann
Tracy P. Hamilton
> I for one would like to see this developed into a FAQ.
I fourth this for PotM.
[snip]
> > I should amend this discussion of the A=40, Argon-Potassium-Calcium
system: I
> > went over it a little too quickly. There are some mistakes in what I
said in
> > the paragraph above, which don't affect any overall conclusions, but
which
> > are actually interesting for evaluating Woodmorappe's article.
I nominate this for erratum of the month - EotM!
--
Tracy P. Hamilton
Adam Marczyk
Perhaps David would be kind enough to combine the two posts into one, so
we'll have one cohesive thing to put on the website in case he wins?
David Ewan Kahana
Hi Adam:
I'll be more than happy to combine the two posts into one for you, that's
no problem. I'll post it probably sometime this weekend.
If I lose ... actually in either case, I'ld certainly consider expanding this
into an FAQ. I can't guarantee that that would be done quickly though. I've
actually read a couple of the FAQs - purely as an intellectual exercise, you
know, not for my own education ;-)
I'ld want to put a bit more work in first, to make sure I don't simply
duplicate any existing material on decay rates.
I can think of a couple of ways of extending the discussion, but nuclear
physics is an extremely rich subject. If Jim, or anyone, can formulate a
question they'ld like to hear addressed, related to the issues raised in this
article and my response, I'ld appreciate the input.
When the talk.origins website is back up, I'll have a look at what already
exists there on radioactive decay.
cheers,
- dave k.
Adam Marczyk
news:3ACCF9AB...@bnl.gov...
Hmm. I think it is back up. But the search script wasn't working, when last
I checked.
James R. Hofmann
I suspect that the most common way in which W's article will be cited is
as evidence that nuclear decay rates should not be assumed to be
constant. This is a common creationist objection. But from the responses
I have read, there are at least two relevant issues.
1. The conditions cited in the article are not relevant to the state of
the earth when rocks solidified and thus the physics involved does not
have any bearing on radiometric dating techniques.
2. W seriously misunderstands the relevant physics.
I think the FAQ should be posed more in terms of the first of these
issues with # 2 coming in in the process. (This ideally would involve
collaboration with a geologist such as Joe Meert.)
How about this as a start:
Have recent discoveries in nuclear physics given support to young earth
creationist claims that nuclear decay rates are inappropriately assumed
to be constant when used to determine geological age?
Thanks,
Jim Hofmann
http://nsmserver2.fullerton.edu/departments/chemistry/evolution_creation/web/
David Ewan Kahana
[snip]
>
> Perhaps David would be kind enough to combine the two posts into one, so
> we'll have one cohesive thing to put on the website in case he wins?
>
Here's the combination of the two posts I made on the AiG article that I
promised to provide for the archives. I made a few modifications to make the
combination read better and I've slightly extended and amplified some of the
physics discussion. I've included the headers for the original post, and the
erratum.
cheers,
- dave k.
From: David Ewan Kahana <d...@bnl.gov>
Newsgroups: talk.origins
Subject: Re: Decay Rates
Date: 28 Mar 2001 17:46:03 -0500
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From: David Ewan Kahana <kah...@sprintmail.com>
Newsgroups: talk.origins
Subject: Re: Decay Rates
Date: 3 Apr 2001 22:53:12 -0400
Organization: little or none
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References: <3ABB8556...@fullerton.edu> <bCRu6.36$9d....@newshog.newsread.com>
<3ABF147C...@hlk.no.hj.spam.se>
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Robert Carroll wrote:
>
> "Sverker Johansson" <l...@hlk.no.hj.spam.se> wrote in message
> news:3ABF147C...@hlk.no.hj.spam.se...
> > Robert Carroll wrote:
> > > "James R. Hofmann" <jhof...@fullerton.edu> wrote in message
> > > news:3ABB8556...@fullerton.edu...
> > > > Any comments on this AIG article on altered decay rates? It postulates
> > > > (very) different conditions in order for the rate involved to be
> > > > different, but it probably will get a lot of publicity.
> > > >
> > > > http://www.answersingenesis.org/docs2001/0321acc_beta_decay.asp
> > > >
> > > >
> > > > Jim Hofmann
> > > >
> > >
> http://nsmserver2.fullerton.edu/departments/chemistry/evolution_creation/web
> > > /
> > > >
> > > >
> > > The argument seems to be that the electron cloud surrounding a nucleus
> > > would provide a strong electromagnetic barrier to a beta particle being
> > > ejected from the nucleus.
> >
> > Not quite. The nucleus itself has an electric field which holds on
> > to electrons around it. With the full complement of normal electrons,
> > there is no room for the new beta-decay electron near the nucleus,
> > so the decay process has to supply enough energy to boost the electron
> > out from the field of the nucleus. If there are no electrons in the
> > K shell, then the decay process only needs enough energy to get an
> > electron from the nucleus into the K shell, which can be significantly
> > less.
>
> Right. I was overlooking nuclear charge. This seems to be the inverse of
> K-electron capture. I'm surprised at the large changes in decay rate,
> though.
>
> Bob
You're right, this process is in fact very like K-capture, but time-reversed,
and with all of the other atomic electrons removed from the picture.
The argument presented in the article is simply bizarre. Anyone who reads it
for very long does so at the risk of suffering severe brain damage. It
contains confusion at near toxic levels. In my opinion a quite careful effort
has been made here to misdirect the reader, and there is an implicit
assumption that the readers will be unsophisticated.
The factor of 10^9 enhancement of the decay rate in fully stripped 187 Re is
indeed extremely surprising on the face of it. I was surprised to hear of
that myself. But it's important to remember that the decay of 187 Re is not
really a very typical beta decay. In fact, in an important sense for the
present discussion, it is the most special naturally occurring beta decay
that we know of. More on this issue later.
naturally occurring nuclear beta decays were very early on shown
experimentally to be directly associated with transitions between discrete
stationary states of the parent and the daughter nucleus, most usually a
transition from the ground state of the parent to the ground state or a low
lying excited state of the daughter.
Depending on the details of the nuclear structure, such a process may or may
not require a large rearrangement of the nuclear state, and may or may not
release a lot of energy. If the only change required in the nuclear state is
a change in the charge state, or equivalently, the z-component of the
isospin, and a readjustment of the nuclear well due to the change in nuclear
Coulomb energy, the transition is generally called super-allowed. Such
transitions are the most favored possible beta decays, and they typically
have small lifetimes, once one corrects for the basic underlying energy
dependence of weak decays.
This energy dependence, by the way, is very strong. For large enough total
decay energies, the dependence is roughly as (W_0)^5 where W_0 is the
endpoint electron energy. For small energies it is even faster than this.
The premier example of a super-allowed beta decay is of course the decay of
the neutron in free space into the proton, with a lifetime of about 1000
seconds. Superallowed decays fall into a group with the lowest possible (ft)
values. Actually one really discusses log_{10} (ft), where t is the half-life
and f is a theoretical factor which corrects for the widely differing total
energies of nuclear beta decays.
The real explanations for sometimes very long beta decay half-lives which are
predicted by theory and *observed* in nature (not `inferred') in quite a few
naturally occurring, neutral, beta unstable atoms is that these atoms can now
1/2- ground state of 187 Osmium with an endpoint energy of W_0 = 2.6 keV. In
fact, this decay has the smallest known naturally occuring beta- endpoint
energy. Even to detect the decay electrons in this system it requires special
experimental techniques. The decay is a so-called unique (meaning only one
It is interesting that Woodmorappe completely omits any discussion in this
article of the case of Potassium-40, which is unstable against decay by
K-capture and positron emission to Argon-40, and by electron emission to
Calcium-40. This is the relevant system for the well known Potassium-Argon,
or Ar/Ar dating technique. The total lifetime of Potassium-40 is 1.265
billion years, and it mainly decays by electron emission to 40 Ca, this
branch accounting for about 89% of all decays in the neutral atom. Almost all
of the other 11% of the decays occur by K-capture, producing 40 Ar.
The total atomic binding in these systems can be estimated from the values in
potassium (Z=19). I estimate that the total binding of the atomic electrons
here is about 15 keV, while the binding of a K-electron in the stripped atoms
would be about 5 keV. Assuming that the binding varies as Z^2, the variation
in atomic binding between Argon, Potassium and Calcium should be on the order
of 10% of the total, say 2-4 keV.
The dominant decay mode of Potassium-40 is a third forbidden Delta-J=4
transition, from the (4-) ground state to the (0+) ground state of
Calcium. The available energy is much larger than it was in Rhenium 187, the
electron endpoint being W_0 ~= 1320 keV. The first excited state (0+) of 40
Ca lies well above the ground state at 3352 keV, and it can just be
ignored. The first excited state (3-) of 40 K is quite low lying at about 30
keV, but it too can safely be ignored at normal temperatures. All of the
decays thus occur from the ground state of Potassium 40.
The difference in the atomic masses of 40 Potassium and 40 Argon is 1503 keV.
This is therefore the total energy available for the decay which is of most
interest in the dating technique. Positron emission to the ground state is
energetically allowed and does occur, but as it turns out, only
rarely. K-capture to the ground state dominates positron emission to the
ground state, and both of these are dominated by K-capture to the first
excited state (2+) which is at 1460 keV. Out of 100 decays of Potassium,
10.66 occur by electron capture to the first excited state of Argon, 0.2 by
electron capture to the ground state of Argon, and 0.001 by positron
emission. The endpoint energy for positron emission is W_0=489 keV (1503 -
2*m_e), on the order of the electron mass. This is certainly not a small
enough number that we have to worry about energy shifts due to binding of
atomic electrons when treating the stripped system: these are, both
relatively and absolutely speaking, far smaller than in the Rhenium-Osmium
case.
On the Argon side of the diagram, I've pointed out there are two states to
consider. There is the 0+ ground state, to which the Q-value in the neutral
system is 1503 keV, and there is also the 2+ first excited state, which lies
1460 keV above the ground state, yielding a very small Q-value of 43 keV. The
transition to the 2+ first excited state has a smaller Delta-J and is only
first forbidden. Clearly, positron emission to this state is not allowed by
energy conservation. Even though the Q value is small, K-capture to this
state is the dominant mode for producing Argon-40. The first excited state
decays to the ground state by emitting a 1460 keV photon (it's an E2
transition.) There can also be various associated X-rays, internal
conversions, and Auger electrons. I won't get into discussing all of these
subtleties.
The 1460 keV secondary gamma ray, incidentally, together with the energetic
electron from the decay to Calcium-40, is likely responsible for a large
fraction of the natural radiation exposure which living creatures receive
over their lifetimes. The source is internal. So in many cases this will
dominate the natural background from the surroundings. This is because
Potassium-40 is a relatively abundant isotope.
Considering all of these facts, we can see that the fully stripped system is
naively expected to have the same decay lifetime, probably to within about
10%. The reasoning is as follows. At least a 10% change comes about because
fully stripped Potassium has no K-electrons. K-capture is therefore not a
possible decay mode for an isolated fully stripped Potassium atom. If the
atom still had one bound electron though, then this decay mode would still be
allowed.
The width for electron emission into the continuum will not be much
affected. On the other hand, positron emission will be more favoured in the
stripped system, since the daughter atom (40-Ar (18+)) has no bound
electrons, and so does the parent (40-K (19+)). This means that the endpoint
energy of the positron decay is larger by one electron mass than it was in
the bare system. We will have W_0 = 489 keV + 511 keV ~= 1000 keV, a change
in the endpoint energy of about a factor of two. If the energy dependence is
as W_0^5, this yields an enhancement by a factor of 32 for positron
emission. In reality the dependence can be expected to be quite a bit faster
at this value of W_0. One might estimate an enhancement on the order of a
factor of 100-200. However, since positron emission was strongly suppressed
in the bare atom, occurring only once in 100,000 decays, this means that it
remains at most a 1% branch in the stripped system. To do better than this
kind of rough estimate will require calculating some numerical integrals.
The conclusion would thus appear to be that fully stripped, isolated
Potassium 40 hardly ever decays to Argon 40 at all. The decay rate should go
nearly to zero, exactly the opposite of the behavior which Woodmorappe
trumpets proudly in the case of Rhenium. Of course, under realistic and
imaginable conditions, where Potassium or Rhenium could actually be fully
stripped, namely in very hot neutral plasmas, we should have to also consider
other reactions, such as capture of continuum electrons, as well as possibly
contributions from additional low lying excited states of the various
nuclei. This statement is valid for Rhenium 187 as well. If these channels
are opened up, it will likely make the total changes in production rates, at
least for Potassium/Argon, rather smaller than what is naively predicted for
the isolated atoms. But these are clearly problems of nucleosynthesis, not of
radioactive dating.
Much the same reasoning applies to yet another case, and I wonder even more
why Woodmorappe ignored this one. Consider the odd-odd nucleus 186 Rhenium,
which beta decays by electron emission to the neighboring nucleus 186
Osmium. Considerations of atomic binding energies are practically the same as
for the case of Rhenium 187, which we just considered in some detail. This
transition is from the 1- ground state of Rhenium 186, and has a branch of
about 75% to the 0+ ground state of Osmium 186 (which, being an even-even
nucleus, is more bound than is Osmium 187). There is also a 23% branch to the
first (2+) excited state of Osmium, as well as smaller branches to two higher
excited states. Both transitions are first forbidden, Delta-J=1, with a
parity change. The endpoint energy of the transition to the 2+ state,
however, is about 930 keV, and that to the ground state is nearer to 1100
shall need to approach charge states of 72+, 73+ or more preferably 74+,
I'd bet, in order to see very strong effects on the beta decay lifetime. If
the K-shell is completely empty in Osmium, then capture to the L-shell is
energetically allowed, but it is greatly suppressed over K-capture. So
perhaps T = 10^8 K might be sufficient. To approach this kind of temperatures
in the current universe, we shall need to make a descent into the core of a
super-giant star. Or perhaps we could wait around for the shock wave of a
supernova explosion to hit us. So while the result discussed in the article
concerning bound state beta decays of fully ionized Rhenium seems possibly to
be very interesting for astrophysics, it is certainly quite irrelevant for
any estimates of the age of terrestrial rocks.
To make this point a little clearer, if it isn't clear enough already,
consider that the binding energy fraction for the electrons in neutral
Rhenium is by my above estimate on the order of:
f (Rhenium) = (500 x 10^3 eV) / (187 x .938 10^9 eV) = 2.85 x 10^-6
David Ewan Kahana
> Here's a suggestion I sent to David Kahana yesterday:
>
> I suspect that the most common way in which W's article will be cited is
> as evidence that nuclear decay rates should not be assumed to be
> constant. This is a common creationist objection. But from the responses
> I have read, there are at least two relevant issues.
>
> 1. The conditions cited in the article are not relevant to the state of
> the earth when rocks solidified and thus the physics involved does not
> have any bearing on radiometric dating techniques.
>
> 2. W seriously misunderstands the relevant physics.
>
> I think the FAQ should be posed more in terms of the first of these
> issues with # 2 coming in in the process. (This ideally would involve
> collaboration with a geologist such as Joe Meert.)
>
> How about this as a start:
>
> Have recent discoveries in nuclear physics given support to young earth
> creationist claims that nuclear decay rates are inappropriately assumed
> to be constant when used to determine geological age?
>
> Thanks,
> Jim Hofmann
> http://nsmserver2.fullerton.edu/departments/chemistry/evolution_creation/web/
I'm a physicist of course, and you can certainly summarize in a short space
what I know about geology, as well as about practical as opposed to
theoretical radioactive dating.
I agree that #1 is the more important issue, and it would certainly help to
have the input of a geologist. #2 would be naturally addressed in the course
of any FAQ answering the question you proposed.
I think the form of the question you've suggested should work quite
well. I've looked at what is available on the talk.origins archive on
isochron dating and the age of the earth. It is actually very nicely
written. This more limited question might serve as an addendum or update to
what is already there, and ought to fit in well enough. Perhaps a link could
be made to it that section of the dating FAQs where the assumption of
constancy of decay rates is discussed.
What I personally might be able to do best is to very quickly outline the
basic theory of beta and alpha decay, and then proceed to discuss each of the
special cases and the experimental results that Woodmorappe raised in the
article. Probably quite a bit of what I've written already could be re-used,
but I would want to shorten and streamline the discussion quite a bit for an
FAQ.
The alternative scenario of the 6,000 year old plasma earth put forward in
the AiG article is easily enough ruled out of course, by various independent
observations. The recent post on non-radiometric dating methods
From: c...@net.commie (Robin Goodfellow)
Newsgroups: talk.origins
Subject: Non-Radiometric Dating
Date: 9 Apr 2001 11:42:55 -0400
Message-ID: <3ad1d750...@netnews.worldnet.att.net>
is helpful in that regard. But it might be useful to address the specific
mechanisms proposed here, and to show that the new experimental results do
not lend any plausibility to the idea of a very young earth, and certainly no
more than it had before these measurements were made.