N2 Vegard–Kaplan System in Absorption

Abstract

Seven bands (6, 0–12, 0), of the N2 Vegard–Kaplan system have been observed in the absorption spectrum of 12 m·atm of gas. The measuring instrument was a 2-m scanning spectrometer with a resolution of about 30 000. Pulse-counting techniques, coupled with the use of a theoretical model based on a measured collision broadening coefficient, have allowed fairly accurate estimates of the transition probabilities of the observed bands. The electronic transition moment has been calculated from the measured transition probabilities and extrapolated with the aid of emission measurements, in order to determine the lifetimes of the system. It is shown that the system has a double lifetime for each vibrational level. The calculated lifetimes [τi(υ′)] for the A 3Σu+ (υ = 0) state were τ2(0) = 1.27 sec for the Σ = 0 substate levels, and τ1(0) = τ3(0) = 2.5 sec for the Σ = 1, −1 substate levels.