Donohoue Deanna L, Bauer Dieter, Cossairt Brandi, Hynes Anthony J
Division of Marine and Atmospheric Chemistry, Rosenstiel School of Marine and Atmospheric Science, University of Miami, 4600 Rickenbacker Causeway, Miami, Florida 33149, USA.
J Phys Chem A. 2006 Jun 1;110(21):6623-32. doi: 10.1021/jp054688j.
A pulsed laser photolysis-pulsed laser induced fluorescence technique has been employed to study the recombination of mercury and bromine atoms, Hg + Br + M --> HgBr + M (1) and the self-reaction of bromine atoms, Br + Br + M --> Br2 + M (2). Rate coefficients were determined as a function of pressure (200-600 Torr) and temperature (243-293 K) in nitrogen buffer gas and as a function of pressure (200-600 Torr) in helium buffer gas at room temperature. For reaction 1, kinetic measurements were performed under conditions in which bromine atoms were the reactant in excess concentration while simultaneously monitoring the concentration of both mercury and bromine. A temperature dependent expression of (1.46 +/- 0.34) x 10(-32) x (T/298)(-(1.86+/-1.49)) cm6 molecule(-2) s(-1) was determined for the third-order recombination rate coefficient in nitrogen buffer gas. The effective second-order rate coefficient for reaction 1 under atmospheric conditions is a factor of 9 smaller than previously determined in a recently published relative rate study. For reaction 2 we obtain a temperature dependent expression of (4.31 +/- 0.21) x 10(-33) x (T/298)(-(2.77+/-0.30)) cm6 molecule(-2) s(-1) for the third-order recombination rate coefficient in nitrogen buffer gas. The rate coefficients are reported with a 2sigma error of precision only; however, due to the uncertainty in the determination of absolute bromine atom concentrations and other unidentified systematic errors we conservatively estimate an uncertainty of +/-50% in the rate coefficients. For both reactions the observed pressure, temperature and buffer gas dependencies are consistent with the expected behavior for three-body recombination.
采用脉冲激光光解-脉冲激光诱导荧光技术研究汞原子与溴原子的复合反应Hg + Br + M --> HgBr + M (1)以及溴原子的自反应Br + Br + M --> Br2 + M (2)。在氮气缓冲气体中，测定了速率系数随压力（200 - 600托）和温度（243 - 293K）的变化关系；在室温下，测定了在氦气缓冲气体中速率系数随压力（200 - 600托）的变化关系。对于反应(1)，在溴原子为过量反应物的条件下进行动力学测量，同时监测汞和溴的浓度。在氮气缓冲气体中，确定了三阶复合速率系数的温度依赖表达式为(1.46 ± 0.34) x 10(-32) x (T/298)(-(1.86 ± 1.49)) cm6 molecule(-2) s(-1)。在大气条件下，反应(1)的有效二阶速率系数比最近发表的相对速率研究中先前测定的值小9倍。对于反应(2)，在氮气缓冲气体中，确定了三阶复合速率系数的温度依赖表达式为(4.31 ± 0.21) x 10(-33) x (T/298)(-(2.77 ± 0.30)) cm6 molecule(-2) s(-1)。速率系数仅报告了2σ精度误差；然而，由于绝对溴原子浓度测定的不确定性和其他未识别的系统误差，我们保守估计速率系数的不确定性为±50%。对于这两个反应，观察到的压力、温度和缓冲气体依赖性与三体复合的预期行为一致。
