Electronic kinetics of molecular nitrogen and molecular oxygen in high-latitude lower thermosphere and mesosphere

A S Kirillov

doi:10.5194/angeo-28-181-2010

Abstract

Abstract. Total quenching rate coefficients of Herzberg states of molecular oxygen and three triplet states of molecular nitrogen in the collisions with O2 and N2 molecules are calculated on the basis of quantum-chemical approximations. The calculated rate coefficients of electronic quenching of O2* and N2* molecules show a good agreement with available experimental data. An influence of collisional processes on vibrational populations of electronically excited N2 and O2 molecules is studied for the altitudes of high-latitude lower thermosphere and mesosphere during auroral electron precipitation. It is indicated that molecular collisions of metastable nitrogen N2(A3Σu*) with O2 molecules are principal mechanism in electronic excitation of both Herzberg states c1Σu&amp;minus, A'3Δu, A3Σu+ and high vibrational levels of singlet states a1Δg and b1Σg+ of molecular oxygen O2 at these altitudes.

Highlights

The study of electronic kinetics of atmospheric components in the region of high-latitude lower thermosphere and mesosphere (80–100 km) is required for a few reasons
May be studies related with laboratory investigations of a discharge in the mixture of N2−O2 shall help in the understanding of the role of these intermolecular processes in electronic kinetics of O2
The calculated rate coefficients are applied in the study of electronic kinetics of N2 and O2 at the altitudes of high-latitude lower thermosphere and mesosphere

Summary

Introduction

The concentrations of atomic oxygen, nitric oxide and other atmospheric components are rather less than concentrations of N2 and O2 and the collisional part of the kinetics of N2 and O2 can be considered in the frames of N2−N2, N2−O2, O2−O2 collisions. Kirillov (2008b) has shown that intermolecular electron energy transfers play a very important role in the processes of the electronic quenching of metastable nitrogen N2(A3 u+) in the collisions with N2 and O2 and singlet oxygen O2(a1 g, b1 g+) in the collisions with O2 These intermolecular transfers are dominant for many vibrational levels of the considered states of N2 and O2. Our calculation of total quenching rate coefficients for Herzberg states of molecular oxygen in the collisions with. Results of our calculations of total quenching rate coefficients for Herzberg states of molecular oxygen are plotted in. The calculation of total quenching rate coefficients for the states of molecular nitrogen in the collisions with N2 includes contributions of intramolecular and intermolecular electron energy transfer processes. We consider three principal processes responsible for the electronic excitation and quenching of triplet N2 and electronically excited O2:

The electronic excitation by auroral electron impact

Spontaneous radiative transitions

Vibrational population of electronically excited N2

Vibrational population of electronically excited O2

Conclusions