Rotational temperature measurements in air and nitrogen plasmas using the first negative system of N 2+

Abstract

Recent Fourier-transform spectrometry measurements of a wide array of rovibrational lines of the first negative system of N 2 + were used to develop a quantitative line-by-line radiation code that can be used for accurate rotational temperature determinations in nitrogen and air plasmas. The model is applied to the interpretation of spectral measurements obtained in a nonequilibrium nitrogen/argon plasma produced by a 50 kW radio-frequency inductively coupled plasma torch. Two rotational temperature determination techniques are presented that consist either in performing a global fit of the spectral region 3700–3920 Å or in comparing the intensity of a single group of isolated lines at 3759.5 Å to the intensity of the (0–0) band head. Both techniques yield a rotational temperature of 4850 K with an accuracy of better than 2%.