The hydrogen molecule H2 in inclined configuration in a weak magnetic field

Highly accurate variational calculations, based on a few-parameter, physically adequate trial function, are carried out for the hydrogen molecule H-2 in inclined configuration, where the molecular axis forms an angle theta with respect to the direction of a uniform constant magnetic field B, for B = 0, 0.1, 0.175 and 0.2 a.u. Three inclinations theta = 0 degrees, 45 degrees, 90 degrees are studied in detail with emphasis to the ground state 1(g). Diamagnetic and paramagnetic susceptibilities are calculated (for theta = 45 degrees for the first time), they are in agreement with the experimental data and with other calculations. For B = 0, 0.1 and 0.2 a.u. potential energy curves E vs R are built for each inclination, they are interpolated by simple, two-point Pade approximant Pade[2/6](R) with accuracy of not less than 4 significant digits. Spectra of rovibrational states are calculated for the first time. It was found that the optimal configuration of the ground state for B <= B-cr= 0.178 a.u. corresponds always to the parallel configuration, theta = 0, thus, it is a (1)Sigma(g) state. The state 1(g) remains bound for any magnetic field, becoming metastable for B > B-cr, while for B-cr < B < 12 a.u. the ground state corresponds to two isolated hydrogen atoms with parallel spins. (C) 2019 Elsevier Ltd. All rights reserved.