Molecular treatment of electron capture at low to intermediate collision energies: Collisions of B4+ ions with H atoms.

Abstract

Partial and total cross sections for electron capture in collisions of B[sup 4+] ions with H atoms from 100 meV/amu to 10 keV/amu have been rigorously determined by using the molecular-orbital expansion method modified by the inclusion of electron translation factors. Quantum-mechanical (3 channels) and semiclassical (12 channels) methods have been employed at collision energies lower than 30 eV/amu and higher than 15 eV/amu, respectively. The agreement of the present results with measurements above 1 keV/amu is reasonable. In our cross sections for the singlet manifold, rather large oscillatory structures are found below 10 eV/amu that are attributable to Stueckelberg-type oscillation. At collision energies below a few eV/amu, the B[sup 3+](1[ital s]3[ital d]) and B[sup 3+](1[ital s]3[ital p]) states are the dominant states for the triplet and singlet manifolds, respectively. However, the B[sup 3+](1[ital s]3[ital p]) state for the triplet and B[sup 3+](1[ital s]3[ital d]) state for the singlet take over above these energies. At energies above 1 keV/amu, three states, the B[sup 3+](1[ital s]3[ital s]), B[sup 3+](1[ital s]3[ital p]), and B[sup 3+](1[ital s]3[ital d]) states, contribute equally to the electron-capture process. A comparison of the present B[sup 4+] results with previous results for different projectiles with the same chargemore » (i.e., Be[sup 4+], C[sup 4+], and N[sup 4+]) reveals that although the cross sections of all these systems lie roughly within a certain range of magnitudes at intermediate collision energies ([ital E]=0.5--10 keV/amu), differences begin to emerge in magnitude and energy dependence below this energy. We examined the scalability of the cross section; some remarks on the scaling are given.« less