THE RADIATIVE ASSOCIATION OF C AND S, C+ AND S, SI AND O, AND SI+ AND O

Rate coefficients for radiative association of carbon and sulfur atoms to form CS, carbon ions and sulfur atoms to form CS+, silicon and oxygen atoms to form SiO, and silicon ions and oxygen atoms to form SiO+ are estimated for temperatures ranging from 300 to 14,700 K. For this temperature range, radiative association rate coefficients (k) are found to vary with temperature (T) as k(CS) = 4.36 x 10(-19) T-0.22+/-0.01 cm(3) s(-1) for CS, k(CS+) = 3.07 x 10(-19) T-0.15+/-0.02 cm(3) s(-1) for CS+, k(SiO) = 5.52 x 10(-18) T-0.31+/-0.02 cm(3) s(-1) for SiO, and k(SiO+) = 6.22 x 10(-18) -4.61 x 10(-22) T + 2.73 x 10(-26) T-2 cm(3) s(-1) for SiO+. Our calculated rate coefficients k(SiO) are higher than the values used in modeling the chemistry of SN 1987A and molecular outflow regions. On the other hand, for Si+ and O, the rate coefficients are one order of magnitude lower than the values used in modeling the chemistry of circumstellar envelopes.