Atomic nitrogen as a probe of physical conditions in the interstellar medium

This is the authors' abstract. We don't add key points for this paper.

Accurate computations of the collision strengths of atomic nitrogen are used to calculate emissivities for transitions from the 4S ground state to the individual levels of the 2D and 2P doublets. The density-sensitive ratio between the intensities of the N I forbidden lines at 5198 and 5200 A is analyzed in an attempt to obtain information about conditions in transition regions of ionization fronts around planetary nebulae and Herbig-Haro objects. Mechanisms for the partial ionization of material lying beyond an ionization front are considered.