No 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.

Recovering a full dimensional quantum rate constant from a reduced dimensionality calculation: Application to the OH+CO→H+CO2 reaction Quantum mechanical calculations of the rate constant for the H2+OH→H+H2O reaction: Fulldimensional results and comparison to reduced dimensionality models

Advances in the time propagation of multidimensional wave packets are exploited to present the A-band photodissociation dynamics of methyl iodide for five active vibrational modes on the three relevant excited ab initiu potential surfaces. The five modes considered represent all of the experimentally observed dynamical activity. The only modes neglected are the asymmetric C-H stretch and the asymmetric deformation of the methyl group. The kinetic energy operator corresponding to these five degrees of freedom is derived. The fully quantum mechanical calculation was implemented upon grids using 2880 distinct time-dependent configurations, determined by the multiconfigurational time-dependent Hartree algorithm, for each electronic state. All of the currently known experimental results regarding the umbrella vibration, symmetric C-H stretching vibration, perpendicular rotation, and parallel rotation of the photodissociated methyl radical fragment are well reproduced. The full wavelength dependence of all of these quantities is determined. The wavelength dependence of the energy deposited into translational, vibrational, and rotational motion is also given. The time evolution of the modes is presented in the context of correlated motion and its effect upon the dissociative process. Many of the details of the dynamics inherent to the conically intersecting nature of the excited surfaces is delineated. In particular it is shown that the Jahn-Teller distortion of the * Q i state is irrelevant in contributing to the perpendicular character of resonance Raman depolarization ratios. Results are compared and contrasted to previous calculations employing the collinear pseudotriatomic model with optimized empirical surfaces or the bent pseudotriatomic model with the same ab initio surfaces.

Quasi-diabatic representations of adiabatic potential energy surfaces coupled by conical intersections including bond breaking: A more general construction procedure and an analysis of the diabatic representation J. Chem. Phys. 137, 22A511 (2012); 10.1063/1.4734315 Direct calculation of coupled diabatic potential-energy surfaces for ammonia and mapping of a fourdimensional conical intersection seam