Barium Hydride Spectra in the Infrared

Quantum analyses of the (1,0), (1,1) and (2,1) bands of the infrared ${}_{}{}^2{}_{}{}^{}\Sigma \to {}_{}{}^2{}_{}{}^{}\Sigma$ system of BaH and some details of the ${}_{}{}^2{}_{}{}^{}\Pi \to {}_{}{}^2{}_{}{}^{}\Sigma$ band at 10,300A are presented. The spin doubling constant $\gamma$ of the upper ${}_{}{}^2{}_{}{}^{}\Sigma$ state is very large (-4.88) and decreases with increasing molecular rotation, $A\cong 625$ ${\mathrm{cm}}^{-1\mathrm{}}$ for the ${}_{}{}^2{}_{}{}^{}\Pi$ state, and a perturbation occurs in the ${}_{}{}^2{}_{}{}^{}\Pi _{\frac{1}{2}d}^{}{}_{}{}^{}$ levels at $J=11\mathrm{}\frac{1}{2}$.