Revealing photofragmentation dynamics through interactions between Rydberg states: REMPI of HI as a case study

Abstract

High energy regions of molecular electronic states are largely characterized by the nature and involvement of Rydberg states. Whereas there are a number of observed dynamical processes that are due to interactions between Rydberg and valence states, reports on the corresponding effect of Rydberg–Rydberg state interaction in the literature are scarce. Here we report a detailed characterization of the effects of interactions between two Rydberg states on photofragmentation processes, for a hydrogen halide molecule. Perturbation effects, showing as rotational line shifts, intensity alterations and line-broadenings in REMPI spectra of HI, for two-photon resonance excitations to the j³Σ⁻(0⁺; v′ = 0) and k³Π₁(v′ = 2) Rydberg states, are analyzed. The data reveal pathways of further photofragmentation processes involving photodissociation, autoionization and photoionization affected by the Rydberg–Rydberg state interactions as well as the involvement of other states, close in energy. Detailed mechanisms of the involved processes are proposed.