Infrared Laser Kinetic Spectroscopy

Abstract

High-resolution infrared spectroscopy has been low in sensitivity and thus it has been almost impossible to observe vibration-rotation transitions of transient molecules. Most infrared studies of such species have thus been conducted in low-temperature inert matrices, whereby structural information has been lost to a large extent. The sensitivity has, however, recently been much improved thanks to introduction of lasers. Infrared diode laser spectroscopy, for example, now allows us to detect molecules as small in number as 10¹⁰, and has in fact been successfully applied to high-resolution spectroscopic studies of transient molecules, free radicals, and molecular ions, which were generated mainly by electrical discharges [1]. The recent development of high-power lasers such as excimer laser and carbon dioxide laser makes it possible to employ such a laser for photochemical generation of transient molecules from an appropriate precursor; an excimer laser pulse typically contains 10¹⁷ photons. In the present study infrared cw diode laser spectroscopy is used to probe the nascent distribution of photofragments, mostly transient molecules, generated by the excimer laser photolysis.