TheEBand System of Calcium Hydride

Abstract

The $E$ band system of CaH at 4900A is shown to be the $\Delta v=0\mathrm{}$ sequence of a ${}_{}{}^2{}_{}{}^{}\Pi \to {}_{}{}^2{}_{}{}^{}\Sigma$ transition, the lower state being the normal ${}_{}{}^2{}_{}{}^{}\Sigma _{}^{+}{}_{}{}^{}$ state. Quantum analysis gives for the $E$, ${}_{}{}^2{}_{}{}^{}\Pi$ state $B_0=4.2844\mathrm{}$, $D_0=-2.16\mathrm{}\times {10}^{-4\mathrm{}}$, $A=9.3\mathrm{}$, $\gamma =+0.230\mathrm{}$ for $K<\mathrm{}20\mathrm{}$, ${\omega }_0=1248.6\mathrm{}$ and ${\omega }_e{x}_e=21.8\mathrm{}$. The large $\gamma$-constant, its changing value for the higher rotational levels and other relations are indications of strong interaction between the $E$ state and other near-lying CaH states. Spin- and $\Lambda$-doubling relations are discussed.