Intramolecular vibrational energy redistribution in toluene: a nine-dimensional quantum mechanical study using the MCTDH algorithm

The intramolecular vibrational energy redistribution within the methyl group of toluene is investigated. A nine-dimensional model potential energy surface in curvilinear coordinates, derived by Cavagnat and Lespade, is adopted along with an exact nine-dimensional kinetic operator in polyspherical coordinates. The quantum calculations are performed with the multiconfiguration time-dependent Hartree (MCTDH) method. MCTDH and some recent extensions of the algorithm are briefly reviewed. We investigate the vibrational energy transfer which is initiated by a local CH-stretch excitation of 1-5 quanta. The redistribution of vibrational energy strongly depends on the initial excitation, being most efficient for the v(CH) = 3 excitation. Selected energy levels are also computed, using a recently developed relaxation scheme as well as the filter-diagonalisation approach. (C) 2004 Elsevier B.V. All rights reserved.