Subject: resonance raman intensities

From: Scott McMillan <[email-masked]>
Date: Wed, 01 May 2002 16:01:31 -0500

Hello,

I am attempting to calculate resonance Raman spectra.  I'm assuming that the 
Duschinsky rotation, non-Condon effects, etc. are not important.  Markham and 
Hudson (J. Phys. Chem. 1996 and J. Raman. Spectrosc. 1998) present two methods 
for calculating resonance Raman spectra.  Their displacement method requires 
ground state geometry, ground state frequency, and excited state geometry 
calculations which I have successfully reproduced.  The resonance Raman 
intensity is then I_k = w_k^2 * delta_k^2, where k is the normal mode and w is 
the frequency.  delta_k is "the actual change in the position of the atoms 
along the kth normal-mode coordinate on excitation divided by the mean-square 
amplitude in the ground-state."  Unfortunately, they do not provide an 
equation or algorithm for calculating delta_k.  My interpretation of this 
statement (the dot-product between the change in the geometry of the ground 
and excited-states with the normal-mode displacement) must be wrong since I 
can't reproduce their calculated spectra.

Peticolas and Rush (J. Comp. Chem., 1995) provide an algorithm for calculating 
delta_k, but it requires the use of internal coordinates.  I'm using 
Gaussian98, which reports all the normal-mode displacements in normalized 
Cartesian coordinates.  Can anyone point me to an algorithm or program that 
can calculate delta_k and/or Raman intensities from quantities that can be 
obtained from Gaussian?

Thanks,
Scott
--
Scott McMillan - [email-masked] 
Institute for Environmental Catalysis
Department of Chemical Engineering, Northwestern University
http://broadbelt.chem-eng.northwestern.edu/~scott/