Band Spectrum of Barium Hydride at 10,000A

A BaH band with principal head at 10,052A degraded to the red is $\mathrm{}(0,0)\mathrm{}{}_{}{}^2{}_{}{}^{}\Pi _{1\frac{1}{2}}^{}{}_{}{}^{}\to {}_{}{}^2{}_{}{}^{}\Sigma$, the lower state being the same as for the other BaH systems. ${B_0}^{*}=3.280\mathrm{}$, $D_0=-1.3\mathrm{}\times {10}^{-4\mathrm{}}$ and the $\Lambda$- doubling is large and negative. This ${}_{}{}^2{}_{}{}^{}\Pi$ state as well as the upper ${}_{}{}^2{}_{}{}^{}\Sigma$ state for the 8924A band must be derived from Ba ${}_{}{}^3{}_{}{}^{}P+\mathrm{H}{}_{}{}^2{}_{}{}^{}S$. The origin of a perturbation in the ${}_{}{}^2{}_{}{}^{}\Pi _{1\frac{1}{2}c}^{}{}_{}{}^{}$ levels at $J=20\mathrm{}\frac{1}{2}$ is discussed.