STRUCTURE AND COUPLINGS IN THE (SI-H)(3-MOLECULE() QUASI)

We have studied the (Si-H)(3+) quasimolecule, treating it as a two-act ive-electron system, calculating adiabatic potentials and wavefunction s for a number of low-lying singlet and triplet states of Sigma(+) and Pi symmetry for 53 internuclear separations. Full configuration inter action has been performed within the two-active electron subspace. We have also calculated nonadiabatic (radial and rotational) dynamical co uplings, including corrections to ensure Galilean invariance. A shallo w 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 cros s section at energy E of 9 Angstrom(2)/ root E/(eV u(-1)) and correspo nding rate coefficient approximate to 3.2 x 10(-10) cm(3) s(-1).