In this project in the Experimental Physical Chemistry Program of the Chemistry Division, Brent Koplitz of Tulane University will investigate site-specific hydrogen-atom production in alkanes, haloalkanes, and organometallic compounds photolyzed under collisionless conditions. The photochemistry of alkyl radicals produced by excimer laser photolysis will be followed using time-of-flight mass spectrometric detection of the Doppler profiles of the hydrogen (deuterium) atoms via their VUV transitions. Ab initio calculations will also be performed to gain additional insight into the photochemistry of the radicals. %%% An understanding of site-specific haloalkane/radical photochemistry is of environmental importance in addition to its role in understanding fundamental photochemical processes in general. The studies supported in this project should impact the understanding of HCFC (hydrochlorofluorocarbon) breakdown in the atmosphere as well as helping to clarify issues involved in the fabrication of semiconductors.