High Resolution Spectroscopy of Chlorine and the Formation of Chlorine

The emission spectrum produced by a corona excited supersonic expansion with He and Cl_ 2 has been extensively studied at high resolution in the region between 410 nm and 490 nm. The most prominent features are due to Cl_ 2^ + and Cl^ + emission. Most of the observed bands of Cl_2 ^+ belong to the A^2Pi _{rm u}-X^2 Pi_{rm g} system. For the Omega=1/2 component bands, the Lambda-type splittings of the rotational lines are resolved for the first time and their parameters are obtained for both the A^2Pi_ {rm u} and X^2Pi _{rm g} states. Molecular constants for the A^2Pi_{ rm u}-X^2Pi_ {rm g} system of ^ {35}Cl_2^+ are determined. Constants for the mixed isotope, ( ^{35}Cl^{37 }Cl)^+, which cannot be predicted directly from the constants of ^ {35}Cl_ 2^ + due to perturbations to the A^2Pi _{rm u} state, have also been determined. In addition, bands which involve new vibrational levels of the upper electronic state are identified. The observed emission lines of the atomic chlorine ions are extraordinarily broadened compared to the Cl _ 2^ + and Cl emission lines. It is determined that this is due to the production of chlorine ions with high kinetic energy and randomly oriented velocities. The reaction mechanism for the formation of these energetic Cl^ + ions is identified in this study; the observed Cl^+ ions are formed from the decomposition of the highly excited state of Cl_2^{2+} which is produced by the reaction of excited state He^+ ions with Cl_2 .