Absorption oscillator strengths for the a′ 1Σ−u–X 1Σ+g and w 1Δu–X 1Σ+g transitions of molecular nitrogen

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Abstract
Measurements have been made of the intensities of absorption bands of molecular nitrogen in the vacuum ultraviolet (vuv) in order to determine the lifetimes of the metastable singlet species a′ 1Σ−u and w 1Δu. The method consists of comparing line and band areas among neighboring features. Interest in these states has recently been heightened by recognition of the energy storing capability of their lowest levels and, in particular, of their role as possible precursors in the formation of NO produced by auroral activity. It is found that the v=0 level of the nitrogen a′ 1Σ−u has a lifetime of 0.013 sec. This is governed by transitions to the ground state. The w 1Δu state, on the other hand, should essentially be radiatively disconnected from the ground state at auroral altitudes due to the lack of collisions. There is no evidence for the w–X transitions at low pressures.