Photodissociation of N2: A significant source of thermospheric atomic nitrogen

In this paper the production rate of atomic nitrogen by photodissociation of N2 is reevaluated taking into account predissociation of the numerous ′Πu and ′Σu valence and Rydberg states of N2 under optically thick conditions. We find that if it is assumed that most of the solar energy absorbed in the 800‐ to 1000‐Å spectral range results in dissociation of N2, the production of N(²D) and N(4S) will be significantly enhanced. Inclusion of this source also requires an upward adjustment of the rate coefficient for quenching of N(²D) by atomic oxygen by ∼50%. This rate coefficient was previously determined aeronomically to be (3.9–4.5) × 10−13 cm³ s−1. Our calculations yield ∼6 × 10−13 cm³ s−1. An accurate knowledge of the rate is essential in calculations of the [N(4S)]/[NO] ratio which is nonlinearly sensitive to O quenching of N(²D).