Representation of Diabatic Potential Energy Matrices for Multiconfiguration Time-Dependent Hartree Treatments of High-Dimensional Nonadiabatic Photodissociation Dynamics

Conventional quantum mechanical characterization of photodissociation
dynamics is restricted by steep scaling laws with respect to the dimensionality
of the system. In this work, we examine the applicability of the multi-configurational
time-dependent Hartree (MCTDH) method in treating nonadiabatic photodissociation
dynamics in two prototypical systems, taking advantage of its favorable
scaling laws. To conform to the sum-of-product form, elements of the
ab initio diabatic potential energy matrix (DPEM) are re-expressed
using the recently proposed Monte Carlo canonical polyadic decomposition
method, with enforcement of proper symmetry. The MCTDH absorption
spectra and product branching ratios are shown to compare well with
those calculated using conventional grid-based methods, demonstrating
its promise for treating high-dimensional nonadiabatic photodissociation
problems.