The effect of electronic autoionisation on the [formula omitted] state vibrational populations

Abstract

Dispersed fluorescence spectroscopy has been employed to study vibrational selectivity accompanying electronic autoionisation in N 2O. Vibrationally resolved fluorescence excitation spectra of the N 2 O + A ∼ 2 Σ + → X ∼ 2 Π transition have been recorded in the photon energy range 16.2–20.7 eV to monitor the formation of (0 0 0), (1 0 0), (2 0 0), (0 0 1) and (1 0 1) A ∼ 2 Σ + state ions. The spectra exhibit prominent structure due to autoionisation from Rydberg states belonging to series converging onto the (0 0 0) C ∼ 2 Σ + limit. Of the five series converging onto this limit, the most significant enhancement in the population of vibrationally excited A ∼ 2 Σ + state ions occurs via autoionisation from the ndσ or ndπ series. Within a single Rydberg series, the degree of vibrational enhancement varies considerably with principal quantum number. Previously unobserved bands in the N 2 O + A ∼ 2 Σ + → X ∼ 2 Π dispersed fluorescence spectrum have been assigned using energy levels determined in photoelectron spectroscopic studies.