Quantum wave-packet dynamics of the photodissociation of LiF

A nuclear wave-packet description of the photodissociation of LiF is described, with emphasis on the dynamics associated with the formation of long-lived resonances. The predissociation is described using ab initio potential-energy curves and transition dipole matrix elements. The split operator method is used to propagate time-dependent coupled-channel wave functions in a diabatic representation. Dissociation is incorporated using absorbing potentials at large internuclear separations to prevent the return of flux from asymptotic regions. Extremely narrow resonances and broad window resonances are found atop a broad absorption envelope, in agreement with a recent stationary-state calculation. The lifetimes of the narrow resonances extend to hundreds of picoseconds, indicating the very slow nature of the dissociation dynamics. The features of the absorption spectrum are connected to specific aspects of the wave-packet motion on the ionic and covalent potential curves through a detailed study of the autocorrelation function.