Condon reflection approximation

Fig. 10.12. The plots show the validity of the reflection approximation over a range of Condon points and collision energies for a typical case.

Before considering the more general methods which provide the full rates, it is interest to reflect upon the results obtained by this simple approximation. Because all the xa < 1 in aromatic hydrocarbons, all the Franck-Condon factors for na 4 0 are unfavorable compared to the case of na = 0. Thus, the molecule would like to keep all the na a minimum and, hence, N at a minimum. 

The dense line structure and the irregularity of the spectral envelope of the C spectrum reflect internal-conversion processes taking place on a time scale of the order of a vibrational period, i.e., several femtoseconds. This is made explicit by directly monitoring the C state electronic population using wavepacket dynamical methods (see Section 3.2). A Gaussian is located initially on the C state surface in the center of the Franck-Condon zone. As discussed above, this corresponds to a broadband excitation of all A2u vibronic levels in the photoelectron spectrum. Seven degrees of freedom and approximately 900 000 basis functions have been included in the expansion, equation (54). The result of the wave-packet... 

---