Fluorescence excitation and emission spectroscopy of the [formula omitted] Rydberg state of ammonia: Assignment of the “Schuster bands of ammonia”

Abstract

Low vibronic levels of the C ̃ ′ 1A′ 1 electronic states of NH 3 and ND 3 have been populated by coherent two-photon excitation. New information about the spectroscopy and the predissociation behavior of these levels has been obtained through analysis of their subsequent C ̃ ′- A ̃ fluorescence. ν 1 is very low in the A ̃ state, being 2300 ± 50 cm −1 for NH 3 and 1790 ± 50 cm −1 for ND 3. Some of the emissions observed from ammonia discharges (the “Schuster bands”), and attributed previously to the ammonium radical, are demonstrated to arise from the C ̃ ′- A ̃ Rydberg-Rydberg transition in ammonia, as recently proposed by Watson.