High-Pressure Afterglow in Nitrogen

Abstract

A MOST remarkable afterglow in nitrogen has been observed at pressures higher than 10 mm. This afterglow has certain properties which would scarcely be looked for in an afterglow at high pressures. The most striking of these is the relatively strong excitation of the Vegard-Kaplan intercombination bands, which originate on the A³Σ -metastable state of nitrogen. Their intensity relative to the usually strong second-positive bands is as high as the intensity in the night-sky afterglow which I reported several years ago¹. The remarkable nature of this phenomenon will be realized when it is pointed out that the weak night-sky glow was produced at pressures of approximately 0.01 mm. by means of a very feeble exciting discharge, while this strong new glow is produced at about 1,000 times that pressure by means of a very strong exciting discharge. In fact, the relative intensity of these bands has been increasing steadily with pressure in the range so far studied. This is an anomalous result in view of the metastability of the A³Σ level. Moreover, the high-pressure afterglow is more intense and has a longer life than similar glows at lower pressures.