Low Energy Resonant Electron Scattering by O₂ and NO

Abstract

Theoretical investigations are made for elastic scattering and vibrational excitation via a vibrationally excited transient ionic state, following the reaction e+AB→AB^−**(υ′)→AB(υ)+e. Restrictions on the electronic wave number k and on the resonant partial wave angular momentum l are such that k<<1 and l≥1. A threshold law is proposed: a resonance width between the vibrational υ and υ′ states, Γ_υ^υ′, is proportional to k^2l+1 multiplied by a square of the Franck-Condon factor F_υ^υ′. This is an extention of the usual Wigner rule, Γ_υ^υ′∝k^2l+1.
The results of semi-empirical calculations are presented for O₂ and NO. By using only one calibration parameter, satisfactory results are obtained. Resonance widths of the transient υ′ states and energy integrated vibrational excitation cross sections are calculated. For the life time of O₂^−**(υ′=4), 7.2×10⁻¹¹sec is obtained. This value is consistent with all available experimental data.