Quantal calculation of the lifetime of N+(5S) and the λ2145Å auroral mystery feature

Abstract The calculated radiative lifetime of the metastable ion is 6.4 × 10−3s. Used in conjunction with the results of measurements by Erdman, Espy and Zipf this sets 1.3 × 10−18 cm2 as the upper limit to the cross section for the formation of N + ( 5 S ) in e - N2 collisions at 100eV which leaves the possibility that the process is responsible for the λ2145 A feature in auroras only just open. The cross section for the formation of N + ( 5 S ) in e — N collisions is large. However for this process to lead to the observed intensity of λ2145 A relative to λ3914 A the N:N2 abundance ratio would have to be as high as 1.6 × 10−2.

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