Negative ions of carbon, nitrogen, and phosphorus

Negative ions of the nitrogen atom have yet to be observed. We estimate the electron affinity of the N^- system to be approximately -0.181 eV using the multiconfiguration Dirac-Fock method. Similar calculations for the neighboring (same row) C^- and (same column) P^- system yield, respectively, 1.210 eV and 0.702 eV, in good agreement with measurements: respectively, 1.263 eV and 0.746 eV. The discrepancies that remain are primarily due to core-core and core-valence correlation effects that have been neglected. The improbability of the existence of a stable N^- system is already evident from a comparison of much simpler calculations with measurements for systems in the same row and neighboring row of the Periodic Table.