The Neutral Nitrogen Spectrum: Term Populations, Multiplet Intensities, Diagnostic Diagrams, and Comparisons with Observations

Abstract

A spectroscopic model of the neutral nitrogen atom is constructed using published radiative rates and derived approximate collisional excitation rates, giving term populations and allowed and forbidden multiplet intensities for a range of electron temperatures and densities. Figures illustrate the predicted variations of the stronger UV and IR multiplet intensities, which are compared with laboratory- and solar-observed UV line intensities and with IR line intensities observed in a number of astrophysical sources. Reasonable agreement is found for all of the compared UV and IR lines, except for one anomalous solar line. Diagnostic diagrams of allowed/allowed, allowed/forbidden, and forbidden/forbidden line ratios in nitrogen are provided and are applied also to other published observations of nitrogen UV and IR lines.