Vibrational Distribution in Late Nitrogen Afterglows

The late portion of long afterglows in nitrogen at a pressure of 1 mm Hg has been investigated spectroscopically, revealing that during 140 sec of decay no change occurs in the characteristic relative vibrational distribution of the N2 (B 3Π→A 3Σ) 1st positive bands. A common excitation mechanism for all levels is required; it cannot depend upon known metastable particles formed in the initial discharge or generated during the decay.