Population of N2(A3Σu+) 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.