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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Thermal decomposition of ClOOCl
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Thermal decomposition of ClOOCl

机译：ClOOCl的热分解

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ClOOCl was prepared in situ in a temperature controlled photoreactor (v = 420 L) by photolyzing OClO/N-2 mixtures in the wavelength range 300-500 nm at temperatures between 242 and 261 K and total pressures between 2 and 480 mbar. After switching off the lights, excess NO2 was added, and IR and UV spectra were monitored simultaneously as a function of time. By spectral stripping of all other known UV absorbers (in particular, other chlorine oxides and chlorine nitrate), we determined rate constants k(-1) of the reaction ClOOCl (+M) -> ClO + ClO (+M) from the first-order decay of the residual UV absorption of ClOOCl at 246 and for the low-pressure limiting rate constant. Application of Troe's expression for the limiting low-pressure rate constants of unimolecular decomposition reactions leads to E-0 = Delta H-r(0)0(ClOOCl -> ClO+ClO) = 66.4 +/- 3.0 kJ mol(-1). k(-1,0) started to fall off from the pressure proportional low pressure behavior at p 30 mbar; however, reliable extrapolation to the high pressure limit was not possible. The decomposition rate constants of ClOOCl were directly measured for the first time, and they are higher, depending on temperature and pressure, by factors between 1.5 and 4.2 as compared to experimental data on k(-1) by Nickolaisen et al. [J. Phys. Chem. 1994, 98, 155] which were derived from the approach of ClO to thermal equilibrium with its dimer ClOOCl. Combination of the present dissociation rate constants with recommended temperature and pressure dependent data on the reverse reaction (k(1)) demonstrate inconsistencies between the dissociation and recombination rate constants. Summarizing laboratory data on k(1) and k(-1) above 250 K and field measurements on the ClO + ClO <-> ClOCCl equilibrium in the nighttime polar stratosphere close to 200 K, the expression K-c = k(1)/k(-1) = 3.0 x 10(-27) exp(8433 K/T) cm(3) molecule(-1) is derived for the temperature range 200-300 K.
机译：通过在242和261 K之间的温度和2和480 mbar之间的总压力下对波长范围为300-500 nm的OClO / N-2混合物进行光解，在温度控制的光反应器（v = 420 L）中原位制备ClOOCl。关掉灯后，加入过量的NO2，并同时监测IR和UV光谱随时间的变化。通过对所有其他已知的紫外线吸收剂（特别是其他氯氧化物和硝酸氯）进行光谱分析，我们从第一个反应中确定了反应ClOOCl（+ M）-> ClO + ClO（+ M）的速率常数k（-1） ClOOCl在246的残余紫外吸收的阶次衰减以及对于低压极限速率常数。 Troe表达式在单分子分解反应的极限低压速率常数中的应用导致E-0 = Delta H-r（0）0（ClOOCl-> ClO + ClO）= 66.4 +/- 3.0 kJ mol（-1）。在p 30 mbar时，k（-1,0）从压力比例低压行为开始下降;但是，无法可靠地推断出高压极限。首次直接测量了ClOOCl的分解速率常数，与温度和压力有关，它们的分解率常数比Nickolaisen等人在k（-1）上的实验数据高1.5到4.2之间。 [J.物理化学[1994，98，155]衍生自ClO及其二聚体ClOOCl达到热平衡的方法。当前解离速率常数与逆反应中推荐的温度和压力相关数据的组合（k（1））证明了解离速率常数与重组速率常数之间存在不一致。总结250 K以上的k（1）和k（-1）的实验室数据以及夜间平流层接近200 K的ClO + ClO <-> ClOCCl平衡的现场测量，表达式Kc = k（1）/ k （-1）= 3.0 x 10（-27）exp（8433 K / T）cm（3）分子（-1）适用于200-300 K的温度范围。

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