Cavity Ring down Spectroscopy: A Review

Over the past decade, cavity ring down spectroscopy has emerged as a powerful technique for performing direct absorption measurements using pulsed lasers. Cavity ring down spectroscopy has since been used from the ultraviolet to the mid-infrared. It is a direct absorption technique, which can be performed with pulsed or continuous light sources and has a significantly higher sensitivity than obtainable in conventional absorption spectroscopy. It can be used to measure the concentration of some light-absorbing substances. Typically, the substances to be measured are in gaseous form. This technique is most widely known as cavity ring-down spectroscopy, although the alternative, but more cumbersome, cavity ring-down laser absorption spectroscopy is preferred by some authors. Here we discuss about the experimental implementation of Cavity ring down spectroscopy and its application to a number of areas of research including laser diagnostics of hostile environments, reaction kinetics and spectroscopy, with particular emphasis on our ongoing studies of the fast (sub-nanosecond) pre dissociation of electronically excited states of small molecules and radicals.