The geometry of the NO2− anion: ab initio calculations and Franck–Condon analysis

Geometry optimization and harmonic vibrational frequency calculations have been performed on the X̃2A1 state of NO2 and X̃1A1 state of NO2−. Franck–Condon analyses and spectral simulations were carried out on the NO2(X̃2A1)–NO2−(X̃1A1) photo-detachment process. In addition, the equilibrium geometry parameters, r(NO)=1.248 ± 0.005 Å and ∠(ONO)=116.8 ± 0.5°, of the X̃1A1 state of NO2−, are derived by employing an iterative Franck–Condon analysis procedure in the spectral simulation. Our conclusions regarding the anion geometry suggest a reinterpretation of the results of Woo et al. [Phys. Rev. A 24 (1981) 1380].