Line-ratio determination of atomic oxygen and N_2(A ~37Sigma;_u ~+) metastable absolute densities in an RF nitrogen late afterglow

摘要

Optical emission spectroscopy line-ratio methods are developed in order to estimate the absolute densities of nitrogen and oxygen atoms and metastable N_2 (A) molecules in the nitrogen late afterglow of an RF discharge, operating at p = 8 Torr, Q = 1 slm and P = 100 W, in what constitutes an extension of the typical domain of application of these methods. [N] is obtained from the first positive (1~+) emission with calibration by NO titration, [O] from the ratio of the NO_β to 1~+ bands, and [N_2 (A)] from the ratios of (i) the NO_γ and NO_β bands, (ii) the second positive (2~+) and NO _β bands and (iii) the 1~+ and 2~+ bands. In addition to the determination of the N, O and N_2 (A) absolute densities, the present investigation gives an indication on the order of magnitude of the rate coefficient of the very important reaction N_2 (X, v 13) + O → NO + N at room temperature.