THEORETICAL-STUDY OF THE X-1-SIGMA+, A1II, C-1-SIGMA-, AND E-1-SIGMA+ STATES OF THE SIO MOLECULE

The self-consistent-field plus configuration-interaction method has been used to compute potential energy curves and certain one-electron properties for the X 1Σ+, C 1Σ-, A 1Π, and E 1Σ+ states of SiO. This study employed a basis consisting of 51 Slater-type orbitals which is an expanded version of the one reported by McLean and Yoshimine. The computed ground-state dissociation energy (De) of 8.1 eV is in excellent agreement with the experimental value of 8.26±0.13 eV. The theoretical ground-state electric dipole moment function is in good agreement with the experimental curve constructed from the microwave data for the v = 0-3 vibrational levels. Einstein A coefficients for vibration-rotation transitions computed from existing theoretical and experimental data are in good agreement. The E 1Σ+ state is shown to dissociate adiabatically to ground-state atoms over a potential barrier with a maximum near 5 bohr. Calculated transition probabilities and radiative lifetimes for the A 1Π-X 1Σ+ and E 1Σ +-X 1Σ+ band systems agree well with recent laboratory experiments. Absorption cross sections as a function of wavelength have been computed and used to determine the opacity of SiO boundary layers that will form on the surface of probe vehicles entering the Jovian atmosphere at high speeds. These calculations demonstrate that the brilliant shock layer emission will be significantly absorbed by the SiO A 1Π-X 1Σ+ and SiO E 1Σ+-X 1Σ+ band systems in the boundary layer in the spectral region between 170 and 230 nm.