Wave-packet dynamics within the multiconfiguration Hartree framework: General aspects and application to NOCl

Abstract

The multiconfigurational time-dependent Hartree (MCTDH) approximation to the time-dependent Schrödinger equation is tested for a realistic three-dimensional example, the photodissociation of NOCl. The working equations of the MCTDH scheme introduced earlier are discussed in some detail. A computational scheme is presented which allows for efficient numerical MCTDH calculations. This scheme is applied to the photodissociation of NOCl after excitation to the S1 surface. The results are compared to the results of an exact wave-packet dynamics calculation. Fast convergence of the MCTDH results toward the exact one is found as the number of configurations is increased. The computation times of the MCTDH calculations are found to be much shorter than those of the exact calculation. Even MCTDH calculations including sufficiently many configurations for a fully converged (quasiexact) description require over two orders of magnitude less CPU time than an exact calculation. The so-called ‘‘natural populations’’ that are computed along with the MCTDH wave packet serve as a check of the degree of convergence without the need to resort to an exact (or more accurate) calculation.