Knowledge Bank

The spectrum of the $N2+$ molecular ion has been photographed from 1200 to 6000 {\AA} at the Dieke Spectroscopy Laboratory of the Johns Hopkins University and at the Spectroscopic Facility of the Argonne National Laboratory. Special hollow cathode sources have been developed to enhance the emission of $N2+$ relative to $N2$ and to permit the transmission of either iron or thorium standard emission lines along the axis of the source without additional optics. The photographic plates have been measured on comparators at the Institute for Molecular Physics of the University of Maryland and the Naval Research Laboratory as well as at Argonne, and cross comparisons of the results have been made in order Co optimize the absolute accuracy of the line positions. The investigation is intended to provide data of such precision as to permit the tabulation of improved absolute energy levels for the lower electronic states of N$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow><mrow\; data-mjx-texclass="ORD">+</mrow>}$. These states are particularly subject to various types of perturbations, as a result of which deperturbation methods must be employed in generating the spectroscopic constants.