Diode laser spectroscopy for monitoring the yield of metastable Cl from photodissociation of simple molecules

Time resolved spectroscopy of the atomic fine structure transition of Cl, 2P1/2–2P3/2 at 882.35 cm−1 is applied to derive relative yields of the metastable level 2P1/2 of Cl(Cl*) from the photodissociation by excimer laser radiation of KrF or ArF. Molecules such as HCl, CH3Cl, CH2Cl2, phenyl chloride, and PCl3 are studied, getting for the first time the possibility of systematic comparison of yields for Cl* and also of earlier results on heavier halogens obtained by other authors using different methods. Most yields determined in the present work are close to a value as calculated from the statistical weights of the two fine structure levels of Cl. This finding is related in a simple diabatic picture to the small spin–orbit interaction in Cl compared to that in iodine. Additionally some rate constants for the collisional quenching of the metastable Cl by the parent molecule are derived.