Knowledge Bank

The author has recently identified six previously unidentified bands in the infrared auroral spectrum as arising from the $A2\pi$ state of $N2+$. The analysis of these bands, which appeared to be related from similarities in band profiles, gave vibrational constants for the lower state that were very close to those for the $X2\Sigma$ state of $N2+$. A systematic discrepancy of a few wave numbers was noted which cannot be explained by observational errors, but which may be due to progressive changes in rotational structure from band to band. The doublet structure of these bands is very similar to the same transition in CN. A re-examination of the relative band intensities indicates that the $A2\pi$ state of $N2+$ lies at $8997cm-1$. An observational test of this identification would be provided by the requirement of a strong band at 9189 {\AA} and a weaker band at 9470 {\AA} in the auroral spectrum.