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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Rate Coefficients for the Propargyl Radical Self-Reaction and Oxygen Addition Reaction Measured Using Ultraviolet Cavity Ring-down Spectroscopy
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Rate Coefficients for the Propargyl Radical Self-Reaction and Oxygen Addition Reaction Measured Using Ultraviolet Cavity Ring-down Spectroscopy

机译：紫外腔衰荡光谱法测量炔丙基自由基自反应和加氧反应的速率系数

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摘要

By using 193 nm laser photolysis and cavity ring-down spectroscopy to produce and monitor the propargyl radical (CH_2CCH), the self-reaction and oxygen termolecular association rate coefficients for the propargyl radical were measured at 295 K between total pressures of 300 Pa and 13300 Pa (2.25 and 100 Torr) in Ar, He, and N_2 buffer gases. The rate coefficients obtained by simple second-order fits to the decay data were observed to vary with the photolytic precursors: allene, propargyl chloride, and propargyl bromide. By using a numerical fitting routine and more comprehensive mechanisms, a distinct rate coefficient for the selfreaction was determined, k_infinity (C_3H_3 + C_3H_3) = (4.3 +- 0.6) * 10~(-11) cm~3 molecule~(-1) s~(-1) at 295 K. This rate coefficient, which is a factor of 2.8 times slower than reported previously, was independent of total pressure and buffer choice over the entire pressure range. Other rate coefficients derived during the modeling included k(C_3H_3 + H 665 Pa He) = (2.5 +- 1.1) * 10~(-10) cm~3 molecule~(-1) s~(-1), k(C_3H_3 + C_3H_3Cl_2) = (7 +- 4) * 10~(-11) cm~3 molecule~(-1) s~(-1), and k(C_3H_3 + C_3H_3Br_2) = (2.4 +- 2) * 10~(-11) cm~3 molecule~(-1) s~(-1). The association reaction C_3H_3 + O_2 was found to lie in the falloff region between linear and saturated pressure dependence for each buffer gas (Ar, He, and N_2) between 300 Pa and 13300 Pa. A fit of these data derived the high-pressure limiting rate coefficient k_infinity (C_3H_3 + O_2) = (2.3 +- 0.5) * 10~(-13) cm~3 molecule~(-1) s~(-1). Three measurements of the propargyl radical absorption cross-section obtained #sigma#_(332.5) = (413 +- 60) * 10~(-20) cm~2 molecule~(-1) at 332.5 nm. Stated uncertainties are two standard deviations and include the uncertainty of the absorption cross section, where appropriate.
机译：通过使用193 nm激光光解和腔衰荡光谱法生产和监测炔丙基（CH_2CCH），在总压力为300 Pa和13300的295 K下测量了炔丙基的自反应和氧分子缔合速率系数在Ar，He和N_2缓冲气体中的Pa（2.25和100 Torr）。观察到通过简单的二阶拟合得到的衰变数据的速率系数随光解前体：丙二烯，炔丙基氯和炔丙基溴而变化。通过数值拟合程序和更全面的机制，确定了不同的自反应速率系数k_infinity（C_3H_3 + C_3H_3）=（4.3 +-0.6）* 10〜（-11）cm〜3分子〜（-1） s〜（-1）在295K。此速率系数比以前报道的速度慢2.8倍，与整个压力范围内的总压力和缓冲液选择无关。在建模过程中得出的其他速率系数包括k（C_3H_3 + H 665 Pa He）=（2.5 +-1.1）* 10〜（-10）cm〜3分子〜（-1）s〜（-1），k（C_3H_3 + C_3H_3Cl_2）=（7 +-4）* 10〜（-11）cm〜3分子〜（-1）s〜（-1），而k（C_3H_3 + C_3H_3Br_2）=（2.4 +-2）* 10〜 （-11）cm〜3分子〜（-1）s〜（-1）。发现缔合反应C_3H_3 + O_2位于300 Pa和13300 Pa之间的每种缓冲气体（Ar，He和N_2）的线性和饱和压力依赖性之间的衰减区域中。这些数据的拟合导出了高压极限速率系数k_infinity（C_3H_3 + O_2）=（2.3 +-0.5）* 10〜（-13）cm〜3分子〜（-1）s〜（-1）。对炔丙基自由基吸收截面的三个测量值是在332.5 nm下获得的σ（332.5）=（413 + -60）* 10〜（-20）cm〜2分子〜（-1）。陈述的不确定度是两个标准偏差，并在适当情况下包括吸收截面的不确定度。

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