Photodissociation spectroscopy and dynamics of the N2O−2 anion

Abstract

The spectroscopy and dissociation dynamics of the N2O−2(C2v) anion have been investigated using the technique of fast ion beam translational spectroscopy. A newly developed pulsed supersonic discharge source is described for the production of internally cold N2O−2. A structured absorption band beginning near 580 nm is observed, and is assigned to the B̃(2A2)←X̃(2B2) transition with the aid of ab initio calculations. Two dissociation channels from the upper state are observed: (1) O−+N2O and (2) NO−+NO. Translational energy and angular distributions are measured for both channels at several excitation energies. The translational energy distribution for channel (1) at 570 nm shows resolved structure corresponding to N2O vibrational excitation. The translational energy distributions for channel (1) are reasonably well described by prior distributions, indicating this channel results from dissociation from the N2O−2 ground electronic state. In contrast, channel (2) appears to result from dissociation on a repulsive excited electronic state. From the translational energy distributions for channel (1), we obtain the bond dissociation energy and heat of formation (at 0 K) for N2O−2: D0(O–N2O)=1.40±0.03 eV and ΔH0f,0(N2O−2)=0.58±0.04 eV.