This research, part of the Experimental Physical Chemistry Program, uses the techniques of laser flash photolysis to produce radicals and transient species, which are then studied by infrared spectroscopic techniques. This research will produce an understanding of the structure and dynamics of prototypical transient species of importance to combustion and chemical bonding. Techniques of time-resolved spectroscopy will be utilized to study the energy levels and dynamics of small radicals such as C2H, C4H, vinyl, vinylidene and allyl. In a second study the absorption spectra of larger radicals will be studied after supersonic cooling. The cooling will reduce the temperature and the number of populated ro-vibrational levels, thereby simplifying the interpretation of the infrared spectra of these species.