KINETIC SPECTROSCOPY OF THE NCl $b^{1}\Sigma^{+}-X^{3}\Sigma^{-}$ $TRANSITION^{a}$

Abstract

Renewed interest in the low-lying metastable electronic states of NCl has been generated by the realization that $NCl(a^{1}\Delta)$ may be used as energy carrier in chemical laser $devices^{a}$. In order to characterize the conditions within a device (local temperature, pressure and concentration) we are currently developing spectroscopic diagnostic based on direct absorption measurements of $NCl b^{1}\Sigma^{+}-X^{3}\Sigma^{-}$ transition. We report studies of the $b^{1}\Sigma^{+}-X^{3}\Sigma^{-}$ system using photolitic generation of NCl, combined with long-path absorption measurements. A CW ring dye laser was used to obtain high resolution (Doppler limited) spectra. Branching ratios for $N_{3}Cl+h\nu \to NCl(X^{3}\Sigma^{-}/a^{1}\Delta) + N_{2}$ were determined for 193 and 248 nm photolysis. Time-resolved measurements provided information about NCl energy transfer and reaction kinetics. The advance of the results of $NCl(a^{1}\Delta)/I$ transfer lasers will be discussed.