Absolute Transition Probability of the Auroral Green Line

Abstract

A MEASUREMENT of the transition probability of the 5577 Å (′S₀–′D₂) auroral line of oxygen is important, not only because this is one of the predominant spectral features of aurorae and the upper atmosphere but also to provide a check on the theoretical predictions for this parameter. The latter is especially important in this case because of the quadrupole nature of the transition involved. Recent work^1–3 here and in other laboratories has shown that there is good agreement between theory and experiment when the relative transition probabilities of multipole lines from the same upper level are considered. Omholt⁴ obtained a value for the 5577 Å transition probability by studying the behaviour of the line in rapidly fluctuating aurorae, but so far no absolute laboratory measurements have been reported for the transition probability of this multipole line. This communication is a preliminary report of such a measurement.