Dissociation dynamics of high-v Rydberg states of molecular hydrogen

Abstract

A high-resolution, state-selective investigation of the decay of (X 2Σg+)np, v′≥9 Rydberg states of H2 into the H(1s)+H(3l) and H(1s)+H(4l) dissociation continua has been performed. The (X 2Σg+)np Rydberg states were excited by double-resonance excitation via the E,F 1Σg+, v=6, J=0 and 1 states, and the H(3l) and H(4l) dissociation products were detected by monitoring the energy-resolved photoelectrons produced by nonresonant photoionization of the fragments. The energy region of interest (138 800–140 000 cm−1) includes the X 2Σg+, v+=9, N+=0–3 ionization thresholds, the H(1s)+H(4l) dissociation threshold, and the H++H− ion-pair threshold. Evidence of both direct and indirect dissociation involving both singly and doubly excited electronic states is observed. Comparisons to the previously observed X 2Σg+, v+=8 constant-ionic-state photoelectron spectrum and the ion-pair spectrum observed in the same energy region reveal strong competition between the ionization and dissociation processes through both rovibrational and electronic interactions.