Electron capture in collisions of S with H+ -: art. no. 062713

Within the framework of a fully quantum-mechanical molecular-orbital close-coupling (QMOCC) theory, charge transfer has been studied for collisions of S with H+. The multireference single- and double-excitation configuration-interaction method was utilized to evaluate the adiabatic potentials and nonadiabatic coupling matrix elements for the SH+ system. Cross sections and rate coefficients are presented for S(P-3,D-1)+H+-> S+(S-4(0),D-2(0),P-2(0))+H with relative collision energies between 0.1 meV/u and 10 keV/u and temperatures between 10 K and 2.0x10(6) K. The investigation shows that the charge-transfer process is dominated by S(P-3)+H+-> S+(P-2(0))+H and that the cross sections and rate coefficients vary by orders of magnitude over the energy and temperature range considered. The current rate coefficients are in disagreement with the often adopted value of 1.30x10(-9) cm(3)/s at low temperatures, and two orders of magnitude smaller than a previous estimate at T=10(4) K, for the process S(P-3)+H+-> S+(D-2(0),P-2(0))+H. We also perfomed semiclassical close-coupling calculations, which give cross sections in excellent agreement agreement with the QMOCC results for energies above 30 eV/u. Application of the results to astrophysical environments is briefly discussed.