Photodissociation of LiFH and NaFH van der Waals complexes: A semiclassical trajectory study

The photodissociation of Li⋯FH and Na⋯FH van der Waals complexes is studied using Tully’s fewest-switches surface-hopping and the natural decay of mixing semiclassical trajectory methods for coupled-state dynamics. The lifetimes of the predissociated excited-state complex (exciplex), as well as the branching ratio into reactive and nonreactive arrangements and the internal energy distribution of the products are reported at several excitation energies. The semiclassical trajectory methods agree with each other only qualitatively, and the results are strongly dependent on the choice of electronic representation. In general, the lifetime of the LiFH exciplex is shorter and less dependent on the excitation energy than the lifetime of the NaFH exciplex. The semiclassical dynamics of LiFH and NaFH are interpreted in terms of the features of their coupled potential energy surfaces.