Rotational temperature measurements in air and nitrogen plasmas using the first negative system of N2+

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 Angstrom or in comparing the intensity of a single group of isolated lines at 3759.5 Angstrom 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%. (C) 2001 Elsevier Science Ltd. All rights reserved.