High Temperature Laser Photolysis in Reflected Shock Waves : Pulse Generation of Radicals and Their Chemical Reactions

点击翻译按钮获取中文摘要

A new method for the pulse generation of radicals in reflected shock waves has been developed to measure the rates of radical-molecule reactions at high temperatures. An intense pulse of ArF (193 nm) or KrF (248nm) laser was used to photolyze O_2, CO_2, NO, H_2S, and C_2H_2 in reflected shock waves. Concentrations of atomic species such as H, O, and N atoms were measured by atomic resonance absorption spectroscopy. By using this method, following results were obtained.(1) It has been shown that O_2 and CO_2 could be photodecomposed at 193 nm in the reflected shock waves via the absorption from vibrationally excited states. It was also shown that O_2 could be phtolysed even at 248 nm by the absorption from v"=7. Vibrational relaxation rates of O_2 in v"=2 and 7 were determined.(2) Rate constants for the reactions of N+H_2 were directly determined at high temperatures for the first time.(3) Non-Arrhenius temperature dependence of the rate constant was found for the H+H_2S reaction. This temperature dependence was explained by a transition state theory based on the quantum mechanical calculation of the transition state.(4) The C_2H radical was produced by ArF laser photolysis of C_2H_2 in reflected shock waves. The rate constants of C_2H+C_2H_2 and C_2H+H_2 reactions were directly determined at high temperatures for the first time.