Photodissociation of F₂ in solid Ar: Electronic state distribution in cage-exit

The role of different electronic states in cage-exit of F atoms for F₂ photodissociation in solid Ar is investigated by nonadiabatic molecular dynamics simulations, using Tully's "Surface-Hopping" approach. The 36 potential surfaces involved are treated by the diatomics-in-molecules (DIM) method. A simulation of 255 Ar atoms in an FCC structure with periodic boundary conditions is used. The results are: (I) Direct cage-exit events are not observed. At least two collisions of the F atoms with the Ar cage are necessary for cage-exit. (II) The total singlet to triplet population ratio at the instant of cage-exit is approximately the statistical one. (III) Some cage-exit events occur for the attractive states ¹ Σ_g⁺, ³Π_u but their role is much smaller than for the caged species. (IV) The Λ quantum number distribution at cage-exit is more uniform than for the caged species. Thus, the electronic state distribution for cage-exit differs greatly from that of the caged species.