Conventions in quadrupolar coupling constant

[Simone Sturniolo]

Hi,

I am trying to run some test simulations on SPINEVOLUTION starting with ab-initio calculated data. I have the value of Vzz and the quadrupolar moment of the nucleus I am testing and am looking to get the right value for the quadrupolar splitting. The nucleus is Lithium 7. The problem is I am missing some factor that I can't understand in my calculations. 

I calculate the coupling constant Chi as e*Q(7Li)*Vzz/h, and this gives me a result of 2830 kHz. The Euler angles are 0, 0, 0, and I am using a single crystallite. I observe three lines symmetric around the centre, as it should be, and the splitting between each pair of lines should be omega_q = 3*pi*Chi. It is instead 1/2*Chi. I can't really understand what am I doing wrong here. If you could clarify me what am I doing wrong I'd be very thankful.

Thank you!

Regards,

Simone Sturniolo

[Mikhail Veshtort]

Hi Simone,

I believe that your expectation to obtain 3*pi*chi for the splitting is incorrect. The splitting should actually be chi/2, just as you observe in the simulation. This can be easily seen, for  example, from Eq. (28) of the SpinEvolution paper in JMR. Just note that V20=(3/sqrt(6))*Vzz.

Best regards,

Mikhail

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