Structure and couplings in the (Si-H)(3+) quasimolecule

We have studied the (Si-H)(3+) quasimolecule, treating it as a two-active-electron system, calculating adiabatic potentials and wavefunctions for a number of low-lying singlet and triplet states of Sigma(+) and Pi symmetry for 53 internuclear separations. Full configuration interaction has been performed within the two-active electron subspace. We have also calculated nonadiabatic (radial and rotational) dynamical couplings, including corrections to ensure Galilean invariance. A shallow minimum, D-e approximate to 0.185 eV is found in the potential curve corresponding to the triplet entrance channel, capable of supporting 11 vibrational levels. Low-energy Si3+ + H charge transfer is expected to be dominated by production of Si2+(3p(21)D) with an estimated cross section at energy E of 9 Angstrom(2)/ root E/(eV u(-1)) and corresponding rate coefficient approximate to 3.2 x 10(-10) cm(3) s(-1).