Research

August 1994

Reply to Comments on "Time-Dependent Theoretical Treatment of Intervalence Absorption Spectra. Exact Calculations in a One-Dimensional Model"

Posted by David Talaga

A polemic in reply to P.N. Schatz and S.B. Piepho (ibid.). The spectra calcd. by S. and P. should not be identical to those the authors calc. The sources of this confusion are the transition dipole and the basis that they use for their expansions. Their spectra are calcd. from model 2, or equivalently, as done by M.J. Ondrechen et al. (1994), using the model 1 potential with a transition dipole given by eq. 5. (The time-dependent methods using these models numerically reproduce their spectra.). Spectra using model 2 must be interpreted either in a basis where the phys. meaning is unclear or as not resulting from an intervalence charge transfer. The time-dependent methods that the authors use in the calcns. provide new phys. insight into intervalence absorption. In the published calcns., the authors chose to use a simple phys. model with the Condon approxn. to illustrate the use of and the insight available from time-dependent calcns. The equations in the original paper are not limited to harmonic diabatic potential bases and can use any form of coupling and any form of the transition dipole moment. This flexibility does not require an increase in computational effort. There is not 1 correct calcn. nor is there a unique selection rule for intervalence charge transfer absorption spectra. The phys. aspects of the problem (mol. geometry, the polarization of the light, requirement of charge transfer, and the symmetry and coordinate dependence of mij) can lead to different spectra.