Experimental and theoretical study of intramultiplet transitions in collisions of C(3P) and Si(3P) with He

Abstract

We present a combined theoretical and experimental study of intramultiplet transitions in collisions of C(3P) and Si(3P) with He. Relaxation rate constants have been measured using the CRESU (Cinétique de Réaction en Ecoulement Supersonique Uniforme) technique at 15 K for C(3P)+He and over the 15–49 K temperature range for Si(3P)+He. Three sets of interaction potentials have been generated for the ∑−3 and ∏3 electronic states of CHe and SiHe systems. Quantum-mechanical calculations have been performed on these potential curves for the spin–orbit relaxation and excitation. Cross sections and rate constants are very sensitive to the interaction potential. For the Si(3P)+He system, an overall good agreement between the theoretical and experimental rate constants is found with the best quality interaction potential, while for the C(3P)+He system experimental rate constants are much smaller than the theoretical ones.