LASER INITIATED CHAIN REACTION STUDIES
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Date
1980
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Ohio State University
Abstract
A new technique has been developed to study systematically the complete, realtime evolution of chemical chain combustion processes. Chain reactions are initiated by radical selective photolysis with low power laser pulses. Time evolution of the populations is obtained spectroscopically by detection of infrared chemiluminescence from specific vibrationally excited products. The technique has been applied to a variety of model chain reaction systems including: $C\ell_{2}/H_{2} S, C\ell_{2}/H_{2}, C\ell_{2}/H_{3}SH, C\ell_{2}/HBr$, and $C\ell_{2}$/hydrocarbons. Each system exhibits a characteristically different behavior depending on the chemistry and the magnitudes of the propagation, termination, and vibrational deactivation rates. By varying the energy density of the laser pulse, initial radical concentrations can be controlled, enabling the study of either the main propagation steps or subsequent radical–radical processes. Analysis of the realtime chain evolution with a corresponding mathematical formalism provides complete quantitative information on the rate constants of propagation, branching, and termination processes, as well as information on transient intermediates. The methods are readily generalized to many combustion systems utilizing other state and product specific spectroscopic probes.
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