Determination of gas temperature from unresolved bands in the spectrum from a nitrogen discharge

A spectroscopic technique is described for determining the gas temperature associated with unresolved bands in the second positive system of the emission spectrum of molecular nitrogen. Projection operators are used in an iterative technique to estimate gas temperature from the shape of a band. The technique is applied to temporally resolved spectra recorded during the glow stage of spark breakdown in nitrogen. The gas temperature is shown to rise from about room temperature at a rate that is in agreement with the electrical power input to the glow discharge. This technique could be of use for studying the effect of gas temperature on the performance of the nitrogen laser.