An analysis and an interpretation of the reported photoelectron spectra of the nitrate anion, NO3-

Abstract

The traditional photo-electron (PE) spectra and the spectra measured by adopting a modern PE spectroscopical method, slow photo-electron velocity-map imaging of cryogenically cooled ion (cryo-SEVI), of the nitrate anion, NO₃^-, reported by Neumark group have been concurrently analyzed on the bases of traditional theories. According to Wigner threshold law, electron kinetic energy (ε) dependences on the anisotropy parameter, β(ε), and on the photo-detachment (PD) cross-section, σ(ε), have been able to be analyzed consistently. The β(ε) observed are analyzed using Cooper-Zare (CZ) and Wigner-Bethe-Cooper-Zare (WBCZ) formulations, the latter of which is one derived from the CZ formulation and Wigner threshold law. The analyses show that the PE of the bands terminating to the vibrationless and ν₄ fundamental levels of the NO₃ X ²A₂′ system have d-and s-wave characters, respectively (i.e. l = 2 and = 0 components, respectively), as the major component of the ejected PE behaviors, while the band terminating to the ν₁ fundamental region, ∼ 1050 cm^-1, has both of the characters, d-and s-waves. The d-and s-wave characters are consistent with the selection rule, ∆l = ±1, and with the characteristic of the highest occupied molecular orbital (HOMO) of the anion, NO₃^-, which is that the non-bonding MO, 1a₂′, mostly consists of in-plane 2p atomic orbital (AO) of the three O's, and of little contribution of that of the central N. The mixed characteristic of the band including the ν₁ fundamental is consistent with results from the laser spectroscopy of the B ²E′ - X ²A₂′ electronic transition of the NO₃ neutral radical, where it has been found that the 3ν₄ (a₁′ ) overtone with l = ±3 closely lies near the ν₁ fundamental.