Population of N₂(A³Σ_u⁺) metastable states in a pure nitrogen glow discharge

Abstract

The concentration of the nitrogen metastable molecule N2(A 3 Sigma u+) is determined in a pure nitrogen glow discharge as a function of the pressure (from 0.1 to 2 Torr) and of the discharge current (up to 30 mA cm-2) using the optical absorption of the first positive system bands. The absorption maximum is of the order of 2% corresponding to a N2(A 3 Sigma u+, nu =0) concentration of about 1.4*1012 cm-3. Measurements of the concentration of nitrogen atoms, the electronic field are also reported. A kinetic model indicates that the N2(A) molecules are created by electronic excitation from ground-state molecules and lost mainly by diffusion to the walls and collisions with N(4S) atoms.