Formation of Si2, C2, C2+ and N2+ by radiative association

Abstract

Rate coefficients for the direct radiative association of silicon atoms to form Si2, carbon atoms to form C2, a carbon atom and a carbon ion to form the C2+ ion, and a nitrogen atom and a nitrogen ion to form the N2+ ion are estimated for temperatures in the range 300 to 14 700 K. For Si2, the rate coefficients (kSi2) increase with an increase of temperature, and they can be expressed by kSi2=2.19 x 10-18 (7/300)0.045 exp (-258.79/T) cm3 s-1 At T ≥ 7100 K, the rate coefficient kSi2 is ≈ 2.5 x 10-18 cm3 S-1 and is independent of temperature. The rate coefficients for C2, C2+ and N2+ in the temperature range 300 to 14 700 K are fitted to the relation k = α (T/300)β exp (- γ/T) cm3 S-1, where α, β and γ are: 4.36 x 10-18 cm3 S-1, 0.35 and 161.31 for C2, 4.01 x 10-18 cm3 S-1, 0.17 and 101.52 for the C2+ ion, and 3.71 x 10-18 cm3 S-1, 0.24 and 26.12 for the N2+ ion, respectively. In each case, the rate coefficients increase with an increase of temperature. © 1997 RAS.