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Shock tube studies of thermal decomposition reactions using ultraviolet absorption spectroscopy.

机译：使用紫外线吸收光谱对热分解反应进行冲击管研究。

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Several elementary thermal decomposition reactions of importance in combustion systems have been investigated using ultraviolet laser absorption spectroscopy and high-temperature shock tube methods. These studies are broken into three categories: (1) the decomposition of alkanes, (2) the incubation and decomposition of CO2, and (3) the decomposition of the benzyl radical and toluene.; The decomposition of ethane, propane, iso-butane, and n-butane were studied over the temperature range of 1297--2034 K and pressure range of 0.13--8.8 atm. The progress of reaction after shock-heating was monitored by measuring methyl radical concentration using laser absorption at 216.62 nm. The rate coefficient determinations were fit using RRKM/master equation calculations using a restricted Gorin model for the transition states.; The thermal decomposition of CO2 was investigated behind shock waves at temperatures of 3200--4600 K and pressures of 0.44--0.98 atm. Ultraviolet laser absorption was used to monitor the CO2 concentration with microsecond time resolution, allowing the observation of a pronounced incubation period prior to steady CO2 dissociation for the first time, confirming the expected bottleneck in collisional activation of this triatomic molecule. Master-equation calculations, with a simple model for collisional energy transfer, were carried out to describe the measured incubation times and decomposition rate coefficient. The master equation calculations suggest that the energy transferred per collision must have a greater than linear dependence on energy.; The decomposition of benzyl and toluene was investigated behind shock waves at temperatures of 1398--1782 K and pressures around 1.5 atm. Benzyl radicals were detected using laser absorption at 266 nm to monitor the progress of reaction. The fast decomposition of benzyl iodide dilute in argon behind shock waves provided an instantaneous benzyl source enabling the measurement of the rate of benzyl decomposition by monitoring the pseudo-first-order decay in benzyl absorption at 266 nm. Rate coefficients for the two-channel toluene decomposition were determined by monitoring benzyl absorption at 266 nm during the shock heating of toluene dilute in argon. RRKM/master equation calculations were carried out for the two-channel toluene decomposition using a restricted Gorin model for the two transition states providing extrapolation of the measured rate coefficients to the high-pressure-limit.
机译：使用紫外线激光吸收光谱法和高温激波管方法研究了燃烧系统中一些重要的基本热分解反应。这些研究分为三类：（1）烷烃的分解，（2）CO 2的孵育和分解，（3）苄基和甲苯的分解。在1297--2034 K的温度范围和0.13--8.8 atm的压力范围内研究了乙烷，丙烷，异丁烷和正丁烷的分解。通过使用在216.62nm的激光吸收测量甲基自由基浓度来监测冲击加热后的反应进程。速率系数的确定使用RRKM /主方程计算进行了拟合，其中使用了受限的Gorin模型来计算过渡态。在3200--4600 K的温度和0.44--0.98 atm的压力下的冲击波后研究了CO2的热分解。使用紫外激光吸收以微秒的时间分辨率监测CO2浓度，从而允许在首次稳定CO2解离之前观察到明显的潜伏期，从而确认了该三原子分子碰撞活化的预期瓶颈。用简单的碰撞能量转移模型进行主方程计算，以描述测得的孵育时间和分解速率系数。主方程计算表明，每次碰撞传递的能量必须大于对能量的线性依赖性。在1398--1782 K的温度和约1.5 atm的压力下的冲击波后研究了苄基和甲苯的分解。使用在266 nm处的激光吸收来检测苄基，以监测反应进程。冲击波后，氩气中稀释的苄基碘快速分解，提供了瞬时苄基源，可通过监测266 nm处苄基吸收的假一级衰减来测量苄基分解的速率。通过在氩气中稀释甲苯的冲击加热过程中监测266 nm处的苄基吸收，可以确定两通道甲苯分解的速率系数。使用受限Gorin模型对两个过渡态进行了两通道甲苯分解的RRKM /主方程计算，从而将测得的速率系数外推至高压极限。

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