Rovibrational energy transfer in collisions of H₂with D₂: a full-dimensional wave packet propagation study

Abstract

We present full-dimensional quantum dynamics calculations for the process of rovibrational energy transfer in collisions between H 2 and D 2 molecules, specificallyRotationally resolved state-to-state cross-sections are obtained for collision energies up to 0.5 eV. From these we calculate rotationally averaged thermal rate coefficients in the temperature range from 100 to 500 K, and compare them with available experimental data. For some transitions, we found it numerically advantageous to compute cross-sections of the reverse collision process and then use microscopic reversibility to obtain the originally sought cross-sections. We employ the Multi-Configuration Time-Dependent Hartree (MCTDH) method for propagating wave packets, and calculate the cross-sections from transition probabilities obtained by the correlation function formalism introduced by Tannor and Weeks. Computations are performed with a potential energy surface that is based on the six-dimensional surface from Boothroyd et al. but reduced in anisotropy, as suggested by Pogrebnya and Clary. The expression of the kinetic energy operator in terms of internal curvilinear coordinates allows us to treat the kinematics of the system exactly, without any decoupling approximations.

Resonances of HCO Computed Using an Approach Based on the Multiconfiguration Time-Dependent Hartree Method

“…Then, it is possible to treat systems that are larger than usual. A typical case is the study of dynamics on conically intersecting surfaces. − MCTDH turned out to be also very efficient for the calculations of cross sections or reaction rates of collisions − or infrared spectra − when a very high level of resolution is not desired, because a very high level of accuracy necessitates long-time propagations.…”

Multi-layer Potfit: An accurate potential representation for efficient high-dimensional quantum dynamics

“…The example system to be considered is the inelastic collision of two H 2 molecules. As our group has studied this system in the past [55][56][57][58][59] using standard MCTDH, here a brief summary of the system details is sufficient.…”

Accuracy of Potfit-based potential representations and its impact on the performance of (ML-)MCTDH

“…Concerning the representation of the wavefunction, major breakthroughs in obtaining accurate results with limited resources were achieved by Meyer and coworkers in developing the multi-configuration time-dependent Hartree method (MCTDH) [4,5,6,7]. MCTDH has proven to be a powerful computational method for highdimensional quantum systems, both for investigating the system dynamics [8,9,10,11,12,13,14] as well as for determining spectroscopic features [15,16,11,17,18,19,20,21,22], where it should be noted that the list of cited works is far from complete. With its multi-layer extension ML-MCTDH [23,24,25], accurate full-dimensional quantum calculations for systems with up to hundreds of degrees of freedom (DOFs) are possible [23,26,27,28,29,30,25,31,32,33].…”