Electronic States and Band Spectrum Structure in Diatomic Molecules. VII.P2→S2andS2→P2Transitions

Abstract

A survey is made of the varied empirical structure-types to be expected for ${}_{}{}^2{}_{}{}^{}P\to {}_{}{}^2{}_{}{}^{}S$ and ${}_{}{}^2{}_{}{}^{}S\to {}_{}{}^2{}_{}{}^{}P$ bands, and examples of these types are discussed individually. In agreement with Kemble's theory, the arrangement of the rotational levels in the ${}_{}{}^2{}_{}{}^{}P$ state changes continuously with the parameter $\frac{\Delta E}{B}$ ($\Delta E=\mathrm{electronic}\mathrm{doublet}\mathrm{separation}$), and these changes are responsible for a large part of the observed variations in band structure. Fig. 1 and Table I show how the arrangement of the ${}_{}{}^2{}_{}{}^{}P$ levels changes with $\frac{\Delta E}{B}$, and Figs. 2-5 show, for the MgH, OH, HgH, and NO $\gamma$ bands, how observed branches are related to energy levels. In Table II, data on $\Delta E$ and $B$ are listed for a number of molecules. The mode of variation of the arrangement of the rotational levels in ${}_{}{}^2{}_{}{}^{}P$ states appears to be in striking agreement with the quantitative formulas of Hill and Van Vleck. For example, if $\frac{\Delta E}{B}=+2\mathrm{}$, their equation becomes formally identical with the Kramers and Pauli formula which holds exactly for the ${}_{}{}^2{}_{}{}^{}P$ state of CH.