  Accurate molecular data for the low-lying states of SiO are computed and used
to calculate rate constants for radiative association of Si and O. Einstein
A-coefficients are also calculated for transitions between all of the bound and
quasi-bound levels for each molecular state. The radiative widths are used
together with elastic tunneling widths to define effective radiative
association rate constants which include both direct and indirect (inverse
predissociation) formation processes. The indirect process is evaluated for two
kinetic models which represent limiting cases for astrophysical environments.
The first case scenario assumes an equilibrium distribution of quasi-bound
states and would be applicable whenever collisional and/or radiative excitation
mechanisms are able to maintain the population. The second case scenario
assumes that no excitation mechanisms are available which corresponds to the
limit of zero radiation temperature and zero atomic density. Rate constants for
SiO formation in realistic astrophysical environments would presumably lie
between these two limiting cases.
