The Rotational Structure of the Blue-Green Bands ofNa2

Abstract

Because of the theoretically impossible structure of these bands as reported by previous observers, the writers have measured them, in absorption, in the third order spectrum of a seven inch plane grating mounted in a forty foot spectrograph. Each band is found, quite definitely, to consist of only one $P$, one $Q$ and one $R$ branch. This accords with Mulliken's theory that the electronic transition is ${}_{}{}^1{}_{}{}^{}P-{}_{}{}^1{}_{}{}^{}S$, and with the nature of the fluorescence series. Moreover the absorption series correlate properly with the fluorescence series. The combination relations have been applied to all measured bands and found to hold, rigorously, within the experimental error, except for the expected $\mathrm{PQR}$ defect, which is very small.