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

Abstract Geometry optimization and harmonic vibrational frequency calculations have been performed on the X 2 A 1 state of NO 2 and X 1 A 1 state of NO 2 − . Franck–Condon analyses and spectral simulations were carried out on the NO 2 ( X 2 A 1 )–NO 2 − ( X 1 A 1 ) photo-detachment process. In addition, the equilibrium geometry parameters, r (NO)=1.248 ± 0.005 A and ∠(ONO)=116.8 ± 0.5°, of the X 1 A 1 state of NO 2 − , 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].