The He⁺₊++N₂O Charge-transfer Reaction at Thermal Energy

Abstract

The ionization and dissociation processes of He⁺+N₂O charge-transfer (CT) reaction have been studied in a flowing afterglow by emission and laser-induced fluorescence spectroscopy. The N₂O+(A²∑⁺-X²∏₁) and N₂⁺+(B²∑u⁺-X²∏g⁺) emission spectra have been identified. The vibrational distribution of N₂O+(A) produced by the He⁺+-FN₂O CT reaction was determined and compared with that produced by the He⁺(2³S)+N₂O Penning ionization which proceeds via a vertical ionization process. The upper limit of the amount of N₂⁺+ ion produced in the B state is estimated to be at most 2% of the total amount of the produced N₂⁺+ ion, which has been obtained by comparing the total emission intensity of N₂⁺+(B-X) with that of N₂O+(A-X). No N₂O⁺(A-X) emission was observed by the He⁺2++N₂O and Ned-N₂OCT reactions, suggesting that the N₂O+(A) state is formed by a cascade from the higher excited electronic state of N₂O⁺. The relative populations in the vibrational levels up to v''=3 were determined by probing the B-X transition. The vibrational distribution of N₂⁺+(X) is inverted, which indicates that dissociation of N₂O+ into the vibrationally excite d N₂⁺+(X) state is an important exit channel for the formation of N₂⁺+ ion in the He⁺+d-N₂O CT reaction.