  Detailed quantum chemistry calculations within the multireference
configuration interaction approximation with the Davidson correction (MRCI+Q)
are presented using an aug-cc-pV6Z basis set, for the potential energy curves
and transition dipole moments between low lying molecular states of singlet
spin symmetry for the SiO molecule. The high quality molecular data are used to
obtain radiative association cross sections and rate coefficients for
collisions between ground state Si and O atoms. Quantal calculations are
compared with semiclassical results. Using a quantum kinetic theory of
radiative association in which quasibound levels are assumed to be in local
thermodynamic equilibrium, we find that resonances play an important role in
enhancing the rate coefficients at low temperatures by several orders of
magnitude from that predicted by standard quantum scattering formulations.
These new molecular formation rates may have important implications for
applications in astrophysics.
