The pressure and temperature dependence of the recombination reaction HO•+SO2+M→HOSO2•+M
The pressure and temperature dependence of the recombination reaction HO•+SO2+M→HOSO2•+M
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DOI：
10.1039/a901596e
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发表时间：
1999-06-01
影响因子：
3.3
通讯作者：
Hippler, H
中科院分区：
文献类型：
--
作者：
Fulle, D;Hamann, HF;Hippler, H
HO的重组。在温度220 ~ 400k，压力1 ~ 96 bar的氦浴气体中，研究了SO2自由基的形成。哈。CH4-O-3混合物在248 nm处激光闪光光解产生自由基，281 nm激发后用饱和激光诱导荧光（SLIF）检测自由基的衰变。从伪一阶条件下的slf时间曲线中提取了热二阶速率常数。由于我们的高压实验，我们进入了衰减范围的很大一部分，这允许对高压极限速率常数进行可靠的外推。我们结合文献中的低压实验，在220、300和400 K处构建了完整的衰减曲线。根据高压极限速率常数k(1,∞)= (1.2 +/- 0.3)x 10(-11) exp(-(360 +/- 100) k /T) cm(3)分子（-1）s（-1）的温度依赖性，我们得出了复合过程的一个小势垒。考虑到这个势垒，我们将低压极限速率常数的温度依赖性表示为k(1,0) = [He] (2.5 +/- 0.7) x 10(-32) (T/300 k)-(3.8+/-0.5) exp(-(360 +/- 100) k /T) cm(6)分子（-2）s（-1）。通过这种新的衰减分析，我们重新分析了文献中各种第三体（Ar, N-2, O-2, CO2, SO2， H2O和SF6）的重组速率常数，可靠地推断出相应的低压极限速率常数，并确定了它们的碰撞效率和每次碰撞传递的平均能量[δ E]（所有）。讨论了对大气化学的影响。
The recombination of the HO. radical with SO2 was studied in the bath gas helium at temperatures between 220 and 400 K and in the pressure range between 1 and 96 bar. HO. radicals were generated by laser flash photolysis of CH4-O-3 mixtures at 248 nm and their decay was detected using saturated laser induced fluorescence (SLIF) following excitation at 281 nm. Thermal second order rate constants were extracted from the SLIF-time profiles under pseudo-first order conditions. Due to our high pressure experiments we accessed a wide part of the falloff range which allowed for a reliable extrapolation towards the high pressure limiting rate constant. We constructed complete falloff curves at 220, 300 and 400 K incorporating the low-pressure experiments from the literature. From the temperature dependence of the high pressure limiting rate constant k(1, infinity) = (1.2 +/- 0.3) x 10(-11) exp(-(360 +/- 100) K/T) cm(3) molecule(-1) s(-1) we conclude on a small barrier for the recombination process. Taking into account this barrier, we express the temperature dependence of the low pressure limiting rate constants as k(1,0) = [He] (2.5 +/- 0.7) x 10(-32) (T/300 K)-(3.8+/-0.5) exp(-(360 +/- 100)K/T) cm(6) molecule(-2) s(-1). With this new falloff analysis we reanalyzed the recombination rate constants in the literature for various third bodies (Ar, N-2, O-2, CO2, SO2, H2O and SF6), reliably extrapolated towards the corresponding low pressure limiting rate constants, and determined their collision efficiencies and the average energies [Delta E](all) transferred per collision. Implications for atmospheric chemistry are discussed.