Is there any proof that electrons can absorb photons?
johnd...@iprimus.com.au
Can someone prove to me its the electrons and not the bonds or holes
that absorb, emit or hold the photon?
Has anyone ever seen with an instrument an electron absorb or emit a
photon?
Do electron beams ever absorb photons or emit photons if you cross
them with laser beams?
Uncle Al
<http://www.phys.ualberta.ca/~gingrich/phys512/latex2html/node102.html>
--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/lajos.htm#a2
to...@cc.usu.edu
Synchrotron and cyclotron radiation, bremsstrahlung processes, etc.
would seem to provide experimentally observed instances of emission
and absorption of radiation from electrons (not bound to an atom).
charlie torre
kushal
What exactly do you mean by saying that "an electron absorbs a
photon"?
Experiments for measuring absorption/emission lines of atoms, show
that electrons absorb/emit energy in quantized amounts. And photon is
nothing more than a packet of quantized electromagnetic energy. So, in
that sense all experiments on measuring absorption or emission lines
of atoms prove that an electron absorbs/emits photons.
And there is also something called single photon detector. With this
one can measure single photon events.
Kushal.
il...@abv.bg
Apparently one can accelarate an electron using an EM field. As the
field is quantised accelaration of the electron obviously follows via
absorbtion of photons.
johnd...@iprimus.com.au
>
> What exactly do you mean by saying that "an electron absorbs a
> photon"?
I'm not sure, goes into or wraps around an electron maybe?
How does a photon even find an electron in a probability cloud?
How do the sizes of a photon and an electron compare to each other?
Tom Roberts
> On Aug 22, 5:17=A0am, kushal <atmabo...@gmail.com> wrote:
>> What exactly do you mean by saying that "an electron absorbs a
>> photon"?
>
> I'm not sure, goes into or wraps around an electron maybe?
Well, you're completely mixing metaphors there.
Electrons clearly do emit photons -- that's quite well established from
atomic transitions to synchrotron light sources. In a sensible theory
the equations are time-reversible, so an electron must be able to absorb
a photon as well -- certainly in QED they do so.
Hmmm. It could be argued that in every case there is a
SYSTEM that emits the photons (an atom, a synchrotron,
etc.), so perhaps it is not established after all.
It's not easy to support that argument -- basically
one would need to construct a theory that does this and
still satisfies the experimental record. Good luck....
Experimentally it is observed that sufficiently-dense plasmas are
opaque, and the electrons are in general far more likely to be involved
in absorbing the photons than any ions.
I'll bet there is a reference to electrons in an atomic trap (e.g. a
Penning trap) absorbing radiation. You can use Google and
scholar.google.com and SPIRES as well as I (this is far from my experience).
> How does a photon even find an electron in a probability cloud?
There's no need to "find" it, interactions simply happen (with various
probabilities, of course, which depend on the overlap of their
wavefunctions). As a rule of thumb: anything that is not prohibited is
mandatory.
> How do the sizes of a photon and an electron compare to each other?
The question does not make sense, as neither has a definite "size". The
regions over which their wavefunctions are nonzero depend more on the
sources of photons and electrons than on the particles themselves.
Tom Roberts
kushal
It will not be correct to think of the photon as having a definite
size and shape. It is just a packet of energy and not really a
particle in the sense of an electron. When we say that "an electron
absorbs a photon", all that we mean is that the electron has gained
some quanta of energy which was in the form of electromagnetic
radiation. So, its all about the absorption or emission of energy.
Nothing more.
Kushal.
holog
as it passes through the medium.
holog
FrediFizzx
news:nzqsk.10902$L_....@flpi150.ffdc.sbc.com...
> johnd...@iprimus.com.au wrote:
>> On Aug 22, 5:17=A0am, kushal <atmabo...@gmail.com> wrote:
>>> What exactly do you mean by saying that "an electron absorbs a
>>> photon"?
>>
>> I'm not sure, goes into or wraps around an electron maybe?
>
> Well, you're completely mixing metaphors there.
>
> Electrons clearly do emit photons -- that's quite well established
> from
> atomic transitions to synchrotron light sources. In a sensible
> theory
> the equations are time-reversible, so an electron must be able to
> absorb
> a photon as well -- certainly in QED they do so.
Electrons do not technically emit or absorb photons. The
energy-momentum from/to photon is absorbed or emitted and photons are
either destroyed or created in the interaction.
Best,
Fred Diether
Co-moderator sci.physics.foundations
Tom Roberts
> "Tom Roberts" <tjrobe...@sbcglobal.net> wrote in message
> news:nzqsk.10902$L_....@flpi150.ffdc.sbc.com...
>
> Electrons do not technically emit or absorb photons. The
> energy-momentum from/to photon is absorbed or emitted and photons are
> either destroyed or created in the interaction.
Quibble all you like about words.
In QED, when a 3-point vertex has two electron legs and a photon leg,
and the time ordering is such that the photon and one electron leg are
incoming and the other is outgoing, we say "the electron absorbed the
photon" [#]. Similarly, in an experiment, when photons impinge on an
electron plasma and do not emerge, we say "the electrons absorbed the
photons". And when a synchrotron has an orbiting electron beam,
radiation emerges from the bending magnets and we say "the electrons
emitted the photons".
Quibble all you like about words, but this is how they are actually
used. "Absorbed" and "emitted" are merely two more names for the
"interaction".
[#] Of course this statement is not frame independent.
Tom Roberts
Hans de Vries
> I'm not sure, goes into or wraps around an electron maybe?
>
> How does a photon even find an electron in a probability cloud?
>
> How do the sizes of a photon and an electron compare to each other?
In QED the (virtual) photons are emitted from a
so called "transition current". This is an interference
pattern between the initial and final state of an
electron.
An electron cloud represents a continuous charge-
and spin-density distribution. An interference
pattern represents an alternating charge and spin
density.
This alternating pattern is the source of the (virtual)
photon. You can obtain the interference current by
working out the Dirac algebra. The photon is then
obtained with the Lienard Wiechert potentials.
For instance, It's the alternating spin density
pattern which is responsible for the transverse
components of the photon.
Regards, Hans de Vries
-----------------------------------------------------
http://www.physics-quest.org
science advisor since 2005 at
http://www.physicsforums.com
FrediFizzx
Yes, that is true but as you can see this sloppy use of language that
is prevalent caused some confusion with the OP in his statement "I'm
not sure, goes into or wraps around an electron maybe?". Photons are
clearly created or destroyed at the interaction vertex. I just wanted
to make that point clear to the OP and others. I know that you know
that.
maxwell
> as I see it the electron is a boat and the photon is the wake it creates
> as it passes through the medium.
>
afterall?
Henrique de Andrade Gomes
to. Otherwise, it is not obvious what you are referring to. -ik ]
I agree with the above. But I do not think these are the type of
answers were what he was aiming for. I think his question goes more
along the lines of Feynman's dialogue with his father, when the latter
asked him if an electron emitted a photon, had the photon been
somewhere inside the electron before emition.