Rebbert R E, Lias S G, Ausloos P
Institute for Materials Research, National Bureau of Standards, Washington, D.C. 20234.
J Res Natl Bur Stand A Phys Chem. 1973 Mar-Apr;77A(2):249-257. doi: 10.6028/jres.077A.017.
The pulse radiolysis of methane has been studied in the absence and presence of electron scavengers such as SF and CDI and positive ion scavengers such as -CD in order to define the role of the intermediates H, C, CH, CH, CH, , and in product formation. The dose rate was varied from 0.68 to 15.2 × 10 eV/g-s, the dose (number of pulses) was varied, and the duration of the pulse was changed from 3 ns to 100 ns. The variation of the yields of the ethylene and ethane products with dose is explained by the reaction of H-atoms with accumulated ethylene product. The fast reacting C, CH, and CH species insert into methane to form acetylene, ethylene, and ethane products, but all of the reactions of these species cannot be completely specified since they may originate in upper electronic states, whose reactions with methane are unknown. Product formation by the slow reacting CH and CH radicals is also examined; for instance, evidence is presented for the occurrence of the reaction: CH + CH → CH + H. Results indicate that the ions and undergo neutralization mainly through the processes When -CD is added, a fraction of the and react with the additive rather than undergo neutralization. A calculation demonstrates that the fraction of ions undergoing reaction with a given concentration of -CD can be correctly predicted by assuming that the rate constant for neutralization of and is the same as that determined recently for the -butyl ion.
为了确定中间体H、C、CH、CH₂、CH₃、 和 在产物形成中的作用，研究了在不存在和存在电子清除剂（如SF₆和CDI）以及正离子清除剂（如β - CD）的情况下甲烷的脉冲辐解。剂量率在0.68至15.2×10¹⁸ eV/g-s之间变化，剂量（脉冲数）也有所不同，脉冲持续时间从3 ns改变到100 ns。乙烯和乙烷产物产率随剂量的变化是由H原子与积累的乙烯产物的反应所解释的。快速反应的C、CH和CH₂物种插入甲烷中形成乙炔、乙烯和乙烷产物，但这些物种的所有反应无法完全确定，因为它们可能起源于较高的电子态，其与甲烷的反应尚不清楚。还研究了反应较慢的CH₃和CH₃自由基的产物形成；例如，给出了反应CH₃ + CH₃ → C₂H₆ + H发生的证据。结果表明，离子 和 主要通过 过程进行中和。当加入β - CD时，一部分 和 与添加剂反应而不是进行中和。一项计算表明，通过假设 和 中和的速率常数与最近测定的丁基离子的速率常数相同，可以正确预测与给定浓度的β - CD反应的离子分数。
