Temperature evaluation from the partially resolved 391 nm N2+band

Abstract

The rotational temperature evaluation method based on only the partially resolved (0,0) emission band of B² Sigma _u⁺-X² Sigma _g⁺ of the N₂⁺ molecule at 391.44 nm is proposed when a low- or medium-resolution power (R=4000 to 12000) transportable spectral instrument has to be used, i.e. to diagnose an industrial plasma source. The band was simulated for large temperatures and apparatus width ranges, and six local peaks on the simulated spectrum were found to be quite sensitive to the temperature evolution; they are composed of the line P26 or complex lines P26+R1, P30+R3, P32+R5, P34+R7, and P36+R9. These local intensity maxima are compared to the band head peak and a practical formula which takes into account the band head shape is proposed for the temperature range of 2000-7000 K. The accuracy on temperature evaluation should be about 6% near 7000 K when the relative peak intensities are known within 3% error. The presented method can be easily used by a spectroscopist not involved in molecule structure.