Ultraviolet Photoelectron Spectrum of NO2-

The 351.1-nm (3.532-eV) photoelectron spectrum of the nitrite anion (NO,) is reported. The electron affinity of NO2 is found to be 2.273 f 0.005 eV, which leads to the heat of formation AfHoo(NOJ = -183.4 f 0.9 k.J/fiol(-43.8 * 0.2 kcal/mol). Vibrational progressions of the symmetric stretch and bending modes of nitrogen dioxide, N02(X2AI), are observed up to 8000 cm-’ above the ground state. Observed fundamental vibrational frequencies of NOIare vl = 1284 f 30 cm-’ (symmetric stretch) and v2 = 776 f 30 cm-’ (bend). The vibrational band intensities are modeled by using a Franck-Condon analysis which explicitly treats the Duschinsky rotation of the normal coordinates between the anion and the neutral molecule. This analysis provides an estimate of the equilibrium geometry of the anion: r , (N-0) = 1.25 f 0.02 A and ( ~ ~ ( 0 N 0 ) = 117.5 * 2 O .