AB-INITIO CALCULATIONS OF ELECTRON-SPIN MAGNETIC-MOMENTS FOR LI, BE AND B-HYDRIDE IN X(2)SIGMA(+) STATES

Electron-spin magnetic moments, in the form of g-shifts, have been com puted at the ROHF level for the X(2) Sigma(+) states of LiH+, BeH2+, L iH-, BeH and BH+. A perturbative approach, complete to second-order in appropriate Breit-Pauli operators, has been used. Retention of two-ce ntre integrals has proven vital. First-order terms are important, espe cially in describing the negative g(1) shifts observed experimentally in (2) Sigma(+) molecules. The relativistic mass correction dominates in first-order, except for LiH- where the two-electron spin-Zeeman gau ge correction supersedes. Second-order terms contribute negatively, an d only to the Delta g(perpendicular to) component. Along the isoelectr onic series LIH(-) --> BeH --> BH+, the magnitude of Delta g(perpendic ular to) increases due to the dependence of spin-orbit coupling on nuc lear charge. The relation of g-shifts to electronic structure and bond ing is explored.