Two relaxation techniques are described, both of which use surface temperature modulation as their basis. In these techniques, modulation of laser light intensity results in a modulation of surface reaction rates. The first technique, a diffusive transport relaxation technique, has been developed to study the chemical reactions occurring under the high pressure conditions used in laser-induced chemical vapor deposition. Perturbation of the reaction rate in a high pressure reactor produces transients in the gas phase reactant and product concentrations for the case of gas phase transport-limited deposition. The product species are differentiated from species formed from the reactant during ionization and fragmentation due to the phase-sensitive nature of the detection scheme. The system response is examined theoretically by examining the response of the gas phase reactant and product concentrations to the modulated surface reaction. The second technique is a new technique which has been developed for obtaining detailed information concerning reaction energetics and pathways of elementary surface reactions. This technique also employs a laser to generate a surface temperature modulation. The laser light is incident on a pure metal film which is mounted within an ultra high vacuum chamber. By modulating the laser intensity, the surface chemical reaction rates are modulated. The combined use of surface temperature modulation and appropriate linearization methods allows a quantitative analysis of the overall reaction energetics to be made. and is used here to investigate the surface processes in a thermal laser-induced reaction.