The formation of SiH$^+$, PH$^+$, and SH$^+$ by radiative association

Cross sections for the radiative association of Si + , P + , and S + with atomic hydrogen to form the diatomic molecular ions SiH + , PH + , and SH + , respectively, are presented. The results are obtained using fully quantum-mechanical techniques and utilize ab initio molecular data calculated with the multireference single- and double-excitation configuration-interaction (MRD-CI) method. Thermal rate coefficients are presented and applications of the results to diffuse interstellar clouds are discussed.