Hyperfine Interaction and Chemical Bonding in MgH, CaH, SrH, and BaH Molecules

Abstract

ESR spectra of MgH, CaH, SrH, and BaH molecules in their ground Σ+2 states were measured while isolated in solid argon matrices at 4°K. The molecules were prepared by quenching metal and hydrogen atom beams in a stream of argon. g tensors and hyperfine structure (hfs) constants for interaction with H, and in the case of MgH, with 25Mg and D, were determined. For 25MgH, | Ψ (0) |2 at Mg and H nuclei were found to be 0.800(8) and 0.0663(2) a.u., respectively, in good agreement with 0.7635 and 0.03789 a.u. recently calculated by Chan and Davidson using a 953 CI wavefunction. It is evident that such elaborate calculations are necessary to obtain accurate theoretical spin densities. Hydrogen hf interaction within the group of molecules indicate less ionicity than in the corresponding diatomic fluorides although the spin density is still predominantly on the metal atoms. Metal p and d contributions are approximately derived from the observed Δg⊥ values and discussed in relation to the united-atom model.