ERROR ANALYSIS FOR COMPLEX KINETICS SYSTEMS METHYL-VINYL CROSS-RADICAL REACTIONS

Many rate constants, particularly for radical-radical reactions, are d etermined in systems exhibiting complex kinetics. Parameters often com prise several species concentrations, absorption cross sections, and r ate constants. They cannot be obtained from an exact analytic expressi on, and therefore, must be solved iteratively through an efficient num erical differential equation solver. We examine here the reaction kine tics of the CH3 and the C2H3 mixed-radical system, generated by excime r laser photolysis of methyl vinyl ketone (MVK) at 193.3 nm. As a mode l, a detailed error analysis for determination of the cross-radical re action rate constant, the initial CH3 and C2H3 radical concentrations are performed using a least-squares modeling program (Acufit). The lea st-squares program, an assumed mechanism, a detailed set of signal-ave raged data, are viewed as the measuring ''instrument.'' The output of the ''instrument'' consists of a ''signal'' that is fit to the data us ing the least-squares criterion. This gives estimated parameters that are examined with respect to random as well as systematic errors. The biases due to uncertainties of each known parameter and combined uncer tainties on the measured parameters are assessed. (C) 1994 John Wiley & Sons, Inc.*