Subject: averaging of hyperfine coupling constants

From: [email-masked] (Bernd Engels)
Date: Mon, 5 Aug 1996 14:04:48 +0200 (MES)

Hi,

For a literature overview I am looking for studies 
which describe the influence of the temperature on the average 
between two proton hyperfine couplings, e.g. the two protons
are distinguishable at 4 K but indistinguishable at 170 K. 
Also other centers could be averaged but protons are more often.
I am mostly interested in studies which uses ab initio or semi-empirical 
methods but others (expecially reviews) are also highly appreciated.

I know that a large number of theoretical studies have dealt 
with the temperature dependence of isotropic hyperfine 
coupling constants.  (Most recently Barone and coworker 
discussed some nice results.)
However, most of the studies are devoted to the changes in
isotropic hfcc's of a single center, e.g. the temperature
effect for a hydrogen center in CH_3 and not on average 
processes as described above.

If you have any comments on the subjects, please let me know.
Thank you very much for all the responses!  

Bernd Engels
e-mail: [email-masked]