Franck-Condon simulation of the S-1 -> S-0 spectrum of phenol

In this paper, a Franck-Condon simulation of the S-1 --> S-0 transition of phenol is given including all normal modes. The geometries of phenol in its S-0 and S-1 states are obtained from CASSCF calculations. The calculated s caled harmonic frequencies are in good agreement with the experimental valu es. To calculate the Franck-Condon factors, Duschinsky rotations between th e S-0 and S-1 states are taken into account. A very strong Duschinsky rotat ion is observed between modes 1 and 18a and modes 9b, 14, and:the OH-bendin g vibration. To get good agreement between experimental and theoretical int ensities, the calculated geometry of the S-1 state is fitted by reducing th e C-O bond length and elongating the molecule along mode 6a. Thus, the most significant changes in geometry in the S-1 state can be deduced from the e xperimentally observed intensity pattern. The program developed to calculat e the Franck-Condon factors is described and tested for the well-known spec trum of the benzene molecule. it is shown how the use of a hash table reduc es storage space which is necessary for a multidimensional Franck-Condon an alysis of large molecules.