The HeH+ molecular ion in a magnetic field

A detailed study of the low-lying electronic states 1Σ, 3Σ, 3Π, 3Δ of the HeH+ molecular ion in parallel to a magnetic field configuration (when α-particle and proton are situated on the same magnetic line) is carried out for B = 0 - 4.414 x 1013 G in the Born-Oppenheimer approximation. The variational method is employed using a physically adequate trial function. It is shown that for the Σ states the parallel configuration is stable with respect to small deviations. The quantum numbers of the ground state depend on the magnetic field strength. The ground state evolves from the spin-singlet 1Σ state for small magnetic fields B ∼< 0.5 au to the spin-triplet 3Σ (unbound or weakly bound) state for intermediate fields and to the spin-triplet strongly bound 3Π state for B ∼> 15 au. When the HeH+ molecular ion exists, it is stable with respect to dissociation