Quantum Mechanics of Beryllium Hydride

The interaction of a normal hydrogen atom with a beryllium atom having the electronic configurations $2s2s$ and $2s2p$, respectively, has been studied by the application of a modified Heitler-London method. It is shown that for beryllium in the ${}_{}{}^1{}_{}{}^{}S$ atomic state, the resulting ${}_{}{}^2{}_{}{}^{}\Sigma$ molecular state is repulsive. For beryllium in the ${}_{}{}^3{}_{}{}^{}P$ atomic state, the ${}_{}{}^4{}_{}{}^{}\Pi$ and ${}_{}{}^4{}_{}{}^{}\Sigma$ molecular states are repulsive, and the ${}_{}{}^2{}_{}{}^{}\Pi$ and ${}_{}{}^2{}_{}{}^{}\Sigma$ states are attractive. For beryllium in the ${}_{}{}^1{}_{}{}^{}P$ atomic state both the ${}_{}{}^2{}_{}{}^{}\Pi$ and ${}_{}{}^2{}_{}{}^{}\Sigma$ molecular states are found to be repulsive. However, when the interaction between the ${}_{}{}^2{}_{}{}^{}\Sigma ({}_{}{}^3{}_{}{}^{}P+{}_{}{}^2{}_{}{}^{}S)$ and the ${}_{}{}^2{}_{}{}^{}\Sigma ({}_{}{}^1{}_{}{}^{}S+{}_{}{}^2{}_{}{}^{}S)$ molecular states is taken into account the lowest ${}_{}{}^2{}_{}{}^{}\Sigma$ state is found to be attractive. The calculated heats of dissociation for the attractive states are in poor agreement with the extrapolated values from the band system.