Pulsed laser powered homogeneous pyrolysis: A computational analysis

The use of the pulsed laser powered homogeneous pyrolysis technique for measuring unimolecular decomposition rate constants under unambiguously homogeneous conditions is investigated by numerical simulation of the experiment. The coupled partial differential equations which govern the gas dynamics and chemical kinetics are solved numerically and the results analyzed. Conditions under which rate constants can be extracted from the experimental data using a simplified analysis are determined. The effects of five sources of error in the simplified analysis are computed. A correlation is presented which may be used to correct for overestimation of the rate constant which is inherent in the simple analysis. Conditions under which the other four sources of error become negligible are presented. Overall, it is expected that this technique will be capable of routinely measuring rate constants within a factor of 2, and will do much better when a high power laser with a uniform beam profile is used and/or a well characterized thermal monitor molecule is available which decomposes with kinetic parameters close to that of the reactant being investigated. © 1994 John Wiley & Sons, Inc.