HYDROGEN MOLECULES IN A SUPERSTRONG MAGNETIC-FIELD - EXCITATION-LEVELS

We study the energy levels of H-2 molecules in a superstrong magnetic field (B greater than or similar to 10(12) G), typically found on the surfaces of neutron stars. The interatomic interaction potentials are calculated by a Hartree-Fock method with multiconfigurations assuming electrons are in the ground Landau state. Both the aligned configurati ons and arbitrary orientations of the molecular axis with respect to t he magnetic-field axis are considered. Different types of molecular ex citations are then studied: electronic excitations, aligned (along the magnetic axis) vibrational excitations, and transverse vibrational ex citations (a constrained rotation of the molecular axis around the mag netic-field line). Similar results for the molecular ion H-2(+) are al so obtained and compared with previous variational calculations. Both numerical results and analytical fitting formulas are given for a wide range of field strengths. In contrast to the zero-field case, it is f ound that the transverse vibrational excitation energies can be larger than the aligned vibration excitation, and they both can be comparabl e to or larger than the electronic excitations. For B greater than or similar to B-crit=4.23 X 10(13) G, the Landau energy of the proton is appreciable and there is some controversy regarding the dissociation e nergy of H-2. We show that H-2 is bound even for B much greater than B -crit and that neither proton has a Landau excitation in the ground mo lecular state.