(2 + n) REMPI of acetylene: Gerade Rydberg states and photorupture channels

Mass analysis studies were performed of ions detected after (2 + n) REMPI of acetylene for resonance excitations to various gerade Rydberg states as a function of laser power. These data, along with STQN/DFT calculations for dissociation of acetylene to C2 + H2, allowed an estimate of a threshold for photodissociation via gerade Rydberg states near 75 000–77 000 cm−1. Mechanisms are proposed regarding (2 + 3) REMPI of acetylene to form C 2 + as well as C+ and H+. Simulation analysis of partly-resolved rotational structured spectra recorded for different jet cooling allowed determinations of precise spectroscopic parameters and lifetime estimates for the Rydberg state, 4p 1Δg00.