THE RESONANCE RAMAN-SPECTRUM OF CH3I - AN APPLICATION OF THE MCTDH APPROACH

The resonance Raman spectrum of CH3I is investigated employing the mul ti-configurational time-dependent Hartree (MCTDH) approach. A general scheme for the calculation of Raman excitation profiles within a MCTDH representation is presented. This scheme is based on a previously des cribed iterative diagonalization approach suitable for MCTDH-wavefunct ions. An empirical four-dimensional potential energy surface is develo ped for the electronic ground state of methyl iodide. The vibrational states corresponding to excitations in these four modes are calculated up to an energy of about 4000 cm(-1). Accurate MCTDH-calculations for the excited, vibronically coupled (3)Q(0)/(1)Q(1) surfaces are perfor med on the ab initio potential energy surface of Amatatsu, Morokuma, a nd Yabushita [J. Chem. Phys. 94, 4858 (1991)]. Based on these dynamica l calculations, Raman excitation profiles are computed for the differe nt relative polarizations of incident and scattered radiation. The dep endence of the depolarization ratio on the amount of C-I stretching ex citation is investigated and interpreted. (C) 1997 American Institute of Physics. [S0021-9606(97)00640-5].