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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Pressure and Temperature Dependence of the Recombination of p-Fluorobenzyl Radicals
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Pressure and Temperature Dependence of the Recombination of p-Fluorobenzyl Radicals

机译：对氟苄基自由基复合的压力和温度依赖性

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The rate constants of the recombination reaction of p-fluorobenzyl radicals,p-F-C_6H_4CH_2+p-F-C_6H_4CH_2 (+M) -> C_(14)H_(12)F_2 (+M),have been measured over the pressure range 0.2-800 bar and the temperature range 255-420 K.Helium,argon,and CO_2 were employed as bath gases (M).At pressures below 0.9 bar in Ar and CO_2,and 40 bar in He,the rate constant k_1 showed no dependence on the pressure and the nature of the bath gas,clearly indicating that it had reached the limiting high-pressure value of the energy-transfer (ET) mechanism (k_(1,infinity)~(ET)).A value of k_(1,infinity)~(ET)(T)=(4.3 +- 0.5) x 10~(-11) (T/300 K)~(-0.2) cm~3 molecule~(-1) s~(-1) was determined.At pressures above about 5 bar,the k_1 values in Ar and CO_2 were found to gradually increase in a pressure range where according to energy-transfer mechanism,they should remain at the constant value k_(1,infinity)~(ET).The enhancement of the recombination rate constant beyond the value k_(1,infinity)~(ET),increased in the order He < Ar < CO_2,and it became more pronounced with decreasing temperature.The dependences of k_1 on pressure,temperature,and the bath gas were similar to previous observations in the recombination of benzyl radicals.The effect of fluorine-substitution of the benzyl ring on k values is discussed.The present results confirm the significant role of radical complexes in the recombination kinetics of benzyl-type radicals in the gas- liquid transition range.The observations on a rate enhancement beyond the experimental value of k_(1,infinity)~(ET),at elevated densities up to the onset of diffusion-control are consistently explained by the kinetic contribution of a "radical-complex" mechanism which is solely based on standard van der Waals interaction between radicals and bath gases.
机译：在0.2-800的压力范围内测量了对氟苄基自由基pF-C_6H_4CH_2 + pF-C_6H_4CH_2（+ M）-> C_（14）H_（12）F_2（+ M）的重组反应的速率常数bar和温度范围255-420 K.氦气，氩气和CO_2被用作熔池气体（M）。在Ar和CO_2压力低于0.9 bar，He压力低于40 bar的情况下，速率常数k_1不依赖于压力和浴槽气体的性质，清楚地表明它已经达到了能量传递（ET）机构的极限高压值（k_（1，infinity）〜（ET））。k_（1，无穷大）〜（ET）（T）=（4.3 +-0.5）x 10〜（-11）（T / 300 K）〜（-0.2）cm〜3分子〜（-1）s〜（-1）为在高于约5 bar的压力下，发现Ar和CO_2中的k_1值在一个压力范围内逐渐增加，根据能量传递机理，它们应保持在恒定值k_（1，infinity）〜（ET）超过k_（1，infinity）〜（ET）值的复合速率常数增加，增加e阶He

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