Hyperfine Interaction and Chemical Bonding in the BeH Molecule

ESR spectra of the BeH and BeD molecules in their ground ²Σ⁺ states were measured while isolated in solid argon matrices at 4°K. g tensors and hyperfine structure (hfs) constants for interaction with ⁹Be, H, and D were determined. ${\text{|Ψ (0)|}}^2$ values at Be and H nuclei were found to be 0.317(2) and 0.0434(2) a.u., respectively, as compared to 0.3223 and 0.0367 a.u. recently calculated by Bender and Davidson using a 1039 CI wavefunction. The HF SCF function of Cade and Huo gave poorer agreement with the measured ${\text{|Ψ (0)|}}_N^2$ values but gave satisfactory agreement with experimental values of $\text{〈(3}{\cos }^2{\theta }_N{\text{−1)/r}}_N^3\mathrm{〉.}$ Approximate spin distributions and bonding among the alkaline‐earth hydride molecules are briefly discussed.