A detailed discussion of the N₂(C ³Π_u) and N₂(X ¹Σ_g⁺) vibrational temperatures in N₂ glow discharges

¹ Laboratório Interdisciplinar de Materials (LABMAT), Universidade Federal de Santa Catarina, 88040-900, Florianópolis, Brazil
² Centre de Physique des Plasmas et leurs Applications (CPAT), Université Paul Sabatier, 31062 Toulouse Cedex, France
³ Departamento de Física, Instituto Tecnológico de Aeronáutica, Centro Técnico Aeroespacial, 12228-900, São José dos Campos, Brazil

Corresponding author: ricard.a@cpat.ups-tlse.fr

Received: 5 December 2002
Revised: 10 December 2003
Accepted: 16 January 2004
Published online: 4 March 2004

Abstract

A N₂ direct current discharge was studied by optical emission spectroscopy. Experimental parameters as gas flow rate (Q), pressure (p) and current (I) were varied independently, covering the following range: 10 < I < 75 mA, 100 < Q < 1000 sccm and 1.7 < p < 10 torr, corresponding to the following plasma parameters: electron density in the range 10⁹−10¹² cm⁻³ and reduced electric field between 3×10⁻¹⁶ and 10⁻¹⁵ V cm⁻². The N₂(C ), N₂(X ) vibrational temperatures and the gas temperature were obtained from the first and second positive systems emissions. The N₂(C ) vibrational distributions did not exhibit a Boltzmann character. A linearization process was employed to such distributions allowing us to calculate the N₂(C ) temperature. The N₂(X ) temperature was calculated from the N₂(C ) one on the basis of the Franck-Condon factors. Results and the method of vibrational temperature calculus are presented.