The Spectrum of Strontium Hydride

Abstract

With a metallic strontium arc in a hydrogen atmosphere as a source, high dispersion spectrograms of three groups of bands in the near infrared with main heads at 7020A, 7347A and 7508A have been obtained. Analysis shows that the latter two groups of bands constitute a ${}_{}{}^2{}_{}{}^{}\Pi \to {}_{}{}^2{}_{}{}^{}\Sigma$ system with only the (0, 0) and (1, 1) vibrational transitions, while the first group represents a transition from a higher ${}_{}{}^2{}_{}{}^{}\Sigma$ to the same normal ${}_{}{}^2{}_{}{}^{}\Sigma$ state. Quantum analyses of the (0, 0) bands give for the normal ${}_{}{}^2{}_{}{}^{}\Sigma$ state ${B_0}^{\prime \prime }=3.6198\mathrm{}$ and ${D_0}^{\prime \prime }=-1.287\mathrm{}\times {10}^{-4\mathrm{}}$, $r_0=2.16\mathrm{}\times {10}^{-8\mathrm{}}$ cm. For the ${}_{}{}^2{}_{}{}^{}\Pi$ state, $A=299\mathrm{}$, ${B_{0,-\frac{1}{2}}}^{\prime }=3.6683\mathrm{}$, ${D_{0,-\frac{1}{2}}}^{\prime }=-1.33\mathrm{}\times {10}^{-4\mathrm{}}$, ${B_{0,+\frac{1}{2}}}^{\prime }=3.6787\mathrm{}$ and ${D_{0,+\frac{1}{2}}}^{\prime }=1.13\mathrm{}\times {10}^{-4\mathrm{}}$. The rotational energy constants for the upper ${}_{}{}^2{}_{}{}^{}\Sigma$ state are ${B_0}^{\prime }=3.8318\mathrm{}$ and ${D_0}^{\prime }=-1.641\mathrm{}\times {10}^{-4\mathrm{}}$. The spin doubling constant ${\gamma }_0$ in the normal state is +0.122, in the upper ${}_{}{}^2{}_{}{}^{}\Sigma$ state it is -3.81, while from the $\Lambda$-type doubling in the ${}_{}{}^2{}_{}{}^{}\Pi$ state $p_0=-3.92\mathrm{}$ and $q_0=-0.398\mathrm{}$. The doubling in the ${}_{}{}^2{}_{}{}^{}\Sigma$, ${}_{}{}^2{}_{}{}^{}\Sigma$ band is much the largest yet found in bands of this type. From the near equality of the $p_0$ of the ${}_{}{}^2{}_{}{}^{}\Pi$ and the ${\gamma }_0$ of the upper ${}_{}{}^2{}_{}{}^{}\Sigma$ and their close agreement with calculated values, it is to be concluded that these two states stand to each other in the relation of "pure precession", as is the case for the corresponding states of CaH. The probable electron configurations are then $\cdots 5p\pi$ and $\cdots 5p\sigma$ for the ${}_{}{}^2{}_{}{}^{}\Pi$ and upper ${}_{}{}^2{}_{}{}^{}\Sigma$ states and $\cdots 4d\sigma$ for the normal state.