Vibrational transition probabilities in the B-X and C-X systems of the SiF radical

Vibrational transition probabilities have been measured for the B ²Σ⁺ (υ′ = 0, 1, 2, 4, 5)-X²Π(υ″=0-10) and C ²Δ(υ′ = 0, 1)-X²Π(υ″ = 0-5) band systems of the SiF radical. Individual B ²Σ⁺ and C ²Δ state vibrational levels were selectively populated by laser excitation of ground state SiF X ²Π prepared in a discharge-flow system. The resultant fluorescence was then dispersed and recorded. Comparison of the observed band strengths with Franck-Condon factors calculated from Rydberg-Klein-Rees potentials allowed the form of the respective electronic transition dipole moment functions to be estimated. The B-X system was found to have an electronic transition probability which did not vary significantly with internuclear separation. In contrast, the observations for the C-X system could only be reproduced by assuming a rapidly decreasing function. These conclusions are consistent with the accepted dominant electronic configurations of the states involved.