Vibrational transition probabilities in the B-X and B′-X systems of the SiCl radical

Vibrational transition probabilities have been measured for the B²Σ⁺(ν′=0-3)-X ²Π(ν″=0-10) and B′²Δ(ν′=0,1)-X²Π(ν″=0-2) systems of SiCl. Individual vibronic levels of the excited states were prepared by laser excitation of ground-state SiCl formed in a discharge-flow system, and the resultant emission was dispersed and recorded. Independent measurements made in two laboratories were in very satisfactory agreement. The extensive results for the B-X system were compared with Franck-Condon factors derived from Rydberg-Klein-Rees potentials, allowing the form of the electronic transition dipole moment function to be assessed. It was found that the electronic transition probability for the B-X system is relatively slowly varying with internuclear distance, consistent with previous conclusions on the electronic configurations of the states involved The more limited data on the strongly diagonal B′-X system were not readily reproduced from the accepted form of the potentials and the anticipated electronic transition dipole moment.