Determination of rotational and vibrational temperatures of a nitrogen helicon plasma

We present a method of rotational and vibrational temperature estimation in nitrogen plasma by simulation of the emission spectrum of the first positive system (B-3 Pi(g)-> A(3)Sigma(+)(u)) of nitrogen. The gas kinetic temperature, assumed to be in equilibrium with the rotational temperature, was obtained from a fit to the experimentally obtained 0 -> 0 at 1051 nm, 1 -> 0 at 872.23 nm, and 2 -> 0 at 775.32 nm rovibrational band spectra. Excellent agreement between values inferred from each band [(499 +/- 29) K] as well as inferred by using the 3 -> 0 band peak ratio method [(473 +/- 25) K] was obtained for a 600 W, 850 G, and 10 mTorr helicon N-2 plasma. The vibrational temperature was determined from a Boltzmann plot of the integrated band intensities [(6040 +/- 225) K] and by numerical fit to the Delta v=+1,+2, and +3 sequences after accounting for Franck-Condon factors and electronic-vibrational transition moments [(6200 +/- 400) K]. (c) 2006 American Institute of Physics.