He2+ molecular ion and the He− atomic ion in strong magnetic fields
AbstractWe study the question of existence, i.e., stability with respect to dissociation of the spin-quartet permutation- and reflection-symmetric 4(−3)+g (Sz=−3/2,M=−3) state of the (ααeee) Coulomb system: the He2+ molecular ion, placed in a magnetic field 0≤B≤10000 a.u. We assume that the α particles are infinitely massive (Born-Oppenheimer approximation of zero order) and adopt the parallel configuration, when the molecular axis and the magnetic field direction coincide, as the optimal configuration. The study of the stability is performed variationally with a physically adequate trial function. To achieve this goal, we explore several helium-containing compounds in strong magnetic fields, in particular; we study the spin-quartet ground state of the He− ion and the ground (spin-triplet) state of the helium atom, both for a magnetic field in 100≤B≤10000 a.u. The main result is that the He2+ molecular ion in the state 4(−3)+g is stable towards all possible decay modes for magnetic fields B≳120a.u. and with the magnetic field increase the ion becomes more tightly bound and compact with a cigar-type form of electronic cloud. At B=1000a.u., the dissociation energy of He2+ into He−+α is ∼702eV and the dissociation energy for the decay channel to He+α+e is ∼729eV, and both energies are in the energy window for one of the observed absorption features of the isolated neutron star 1E1207.4-5209.