C2(X1Σg＋)自由基与不饱和碳氢化合物反应的温度效应

Temperature Dependence of C_2(X_1Σ_g^+) in Reactions with Unsaturated Hydrocarbons

运用脉冲激光光解-激光诱导荧光(PLP-LIF)的方法在293-573K的温度范围内测量了C2(X1Σ+g)自由基与不饱和碳氢化合物(C2H4和C2H2)气相反应的双分子反应速率常数.获得的速率常数可以用Arrhenius公式表达如下(单位:cm3·molecule-1·s-1):k(C2H4)=(1.16±0.10)×10-10exp[(290.68±9.72)/T],k(C2H2)=(1.36±0.02)×10-10exp[(263.85±7.60)/T],误差为2σ.由获得的双分子反应速率常数及其所呈现的负温度效应,我们认为在293-573K温度范围内C2(X1Σ+g)自由基和不饱和碳氢化合物的反应遵循加成机理.

Bimolecular rate constants for the gas-phase reactions of C2（X1Σ＋g） with unsaturated hydrocarbons C2H 4 and C2H 2 were measured over the temperature range 293-573 K by pulsed laser photolysis/laserinduced fluorescence（PLP-LIF）.The rate constants,in the unit of cm 3 · molecule-1 · s-1,can be fitted by the normal Arrhenius expressions：k（C2H 4）=（1.16±0.10）×10-10 exp[（290.68±9.72）/T],and k（C2H 2）=（1.36±0.02）× 10-10 exp[（263.85 ± 7.60）/T],where all error estimates are ± 2σ and represent the precision of the fit.The observed bimolecular rate constants along with the negative temperature dependences of k（T） allow us to conclude that the reactions of C2（X1Σ＋g） with these unsaturated hydrocarbons in the temperature range 293573 K proceed via an addition mechanism.