Magnetic Properties of the BH Molecule

Abstract

The unusual magnetic properties of the 1Σ+ BH molecule calculated earlier from perturbed (coupled) Hartree—Fock theory have been confirmed, and rendered more nearly gauge invariant. Predictions of the spin—rotation constant for hydrogen are CH=−14.9 kc/sec with B as origin, and CH=−18.2 kc/sec with H as origin, as compared with the earlier values of −8.5 and −25.3 kc/sec, respectively. Also, the shielding at H is σH=24.46 ppm with B as origin and σH=25.44 ppm with H as origin, as compared with our previous values of 22.55 and 27.62 ppm, respectively. In addition, we present an interpretation of the molecular paramagnetism, the antishielding at B, and the large spin—rotation constant of B, in terms of orbital current densities. It is found that these extreme properties calculated for BH result from a paramagnetic current due to excitations of the lone-pair electrons on the boron atom to an unoccupied pπ orbital on this atom.