Electron-Spin Magnetic Moment (g Factor) of X2Σ+ Diatomic Radicals MX(±) with Nine Valence Electrons (M = Be, B, Mg, Al; X = N, O, F, P, S, Cl). An ab Initio Study

Abstract

The electron-spin g shifts (magnetic moments μS) of X2Σ+(1π43σ) radicals MX(±) with nine valence electrons are calculated at their equilibrium geometries, using second-order perturbation theory, a Hamiltonian based on Breit−Pauli theory, and correlated (MRCI) wave functions. Eighteen diatomics have been studied: BeF, BeO-, BeCl, MgF, MgO-, and MgCl (class I); BF+, BCl+, AlF+, and AlCl+ (class II); and BO, BN-, BS, BP-, AlO, AlN-, AlS, and AlP- (class III). Most radicals have small Δg∥ values (≈−100 ppm) and large negative Δg⊥ values (−800 to −8500 ppm), except for AlN- and AlP-, which have positive Δg⊥ values (1400 and 10 000 ppm) due to the quasi-degeneracy X2Σ+/12Πi. The sum-over-states expansions for Δg⊥ are dominated in classes I and II by the coupling with 12Πr, and in class III with both 12Πi and 22Πr. The 2Πr(3σ→2π) state always contributes negatively, whereas 2Πi(1π→3σ) contributes positively for most radicals but negatively for the boron series BO, BN-, BS, and BP-. Experimental g shifts, which ...