PUB - Publikationen an der Universität Bielefeld

A novel time-dependent algorithm for the simulation of the nuclear dynamics in floppy triatomic molecules is presented. The algorithm is based on hyperspherical coordinates and harmonics and exploits the full three particle permutation-inversion symmetry. It is not restricted to zero angula momenta. The wavepacket is represented using a basis set of symmetrized hyperspherical harmonics and the time dependency of the wavepacket is retained in the expansion coefficients which are functions of one hyperspherical coordinate, the hyperradius, only. The time-dependent Schrödinger equation is solved numerically using short-time propagators and a grid representation for the hyperradius. The novel method is used to calculate the bound ro-vibrational energies of H3+ (J <= 4) using the sub-microhartree accuracy potential energy surface of W. Cencek et al. The data obtained are in excellent agreement with recent time-independent results. A comparison of the time-independent results (J <= 10) with the comprehensive compilation of experimental data below 9000 cm-1 by Lindsay et al. shows deviations of up to 1.2 cm-1. It is shown that these deviations exihibit a systematic influence of the vibrational band but depend to a much lesser extent on rotational excitation. The remaining discrepancies can be attributed to the neglect of non-adiabatic effects for which a useful correction formula is obtained. The scatter in individual bands can thus be reduced to ~ 0.1 cm-1 such that our corrected results are consistent with the accuracy of the potential energy surface itself.