SENSITIVITY AND CORRELATION-ANALYSIS OF THE PHYSICAL PARAMETERS IN ABSORPTION, 4-WAVE-MIXING, AND SCHLIEREN EXPERIMENTS

Experimental data that are used to determine rate coefficients depend not only upon reaction rates but also the physical properties of the m easured species. Sensitivity coefficients are presented for the physic al parameters of three general experimental techniques: a signal linea rly dependent on the concentration of a species, a signal quadraticall y dependent on concentration, and a schlieren signal, which depends up on a bulk property of the system. With these, both the physical and ch emical parameters of a model may be treated on a comparable basis. The similarities and differences between these techniques are illustrated in a simple example of radical formation via first-order precursor de composition followed by second-order recombination. The results are th en applied to two important examples: H-2 + O-2 and CH3 + CH3. In almo st all cases, the experimental data contains more information about th e physical parameters, such as the optical cross section, than the kin etic rate coefficients. Furthermore, if a physical parameter is not pr operly treated; strong correlations between it and rate coefficients w ill introduce significant systematic biases in the rate coefficient. ( C) 1995 John Wiley and Sons, Inc.