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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Kinetics and Products of the Reactions BrO + DMS and Br + DMS at 298 K
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Kinetics and Products of the Reactions BrO + DMS and Br + DMS at 298 K

机译：BrO + DMS和Br + DMS在298 K反应的动力学和产物

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摘要

The kinetics of the reaction BrO + DMS -> products (1), were examined by use of pulsed-laser photolytic generation and time-resolved detection of the BrO radical by absorption spectroscopy at total pressures of 60, 100, and 200 Torr N_2 (1 Torr = 133.322 Pa). A value of k_1 = (4.40 +- 0.66) * 10~(-13) cm~3 s~(-1) was obtained independent of pressure at 295 K. This value is significantly higher than that determined previously in low-pressure (< 4 Torr He), discharge flow measurements (2.6 * 10~(-13) cm~3 s~(-1)). By observing the formation of DMSO directly, we obtain a value of 1.17 +- 0.34 for its yield in reaction 1; the major uncertainty is the +- 30% in the DMSO cross section. The impact of these results on the chemistry of the remote marine boundary layer was assessed using a chemical box model. At daytime concentrations of 1-2 pmol/mol, the BrO radical was found to be an important sink for DMS and the dominant source of DMSO. In a second set of experiments, pulsed-laser photolysis coupled with resonance fluorescence detection of Br atoms was employed to study the equilibrium kinetics of Br + DMS + M reversible Br - DMS + M (4, -4) at 100 Torr N_2 and 295 K. Values of k_4 = (6.36 +- 0.43) * 10~(-11) cm~3 s~(-1) and k_(-4) = (1.02 +- 0.07) * 10~4 s~(-1) were obtained, and were used to calculate the equilibrium constant K_4 = (6.24 +- 0.56) * 10~(-15) cm~3. The uncertainty is 2#sigma# plus estimated systematic error. At high [Br] ((1-3) * 10~(12) cm~(-3)), Br atoms are lost from equilibrium via the fast reaction Br + Br - DMS -> Br_2 + DMS (5), and a value of k_5 = (4.2_(-1.2)~(+2.3) * 10~(-10) cm~3 s~(-1) was obtained. The uncertainty is 2#sigma# plus the major systematic error incurred by estimating [Br]_o from laser fluence measurements. Pulsed-laser photolysis combined with time-resolved UV absorption at selected wavelengths and diode array measurements in the wavelength range 300-450 nm showed a strong absorption centered at 365 nm due to Br-DMS. A value of #sigma#_(-1.1)~(+1.6) * 10~(-17) cm~2 was obtained by fitting to the time-resolved absorption signal due to Br-DMS. The uncertainty is 2#sigma# plus systematic error (as above).
机译：通过在60、100和200 Torr N_2的总压力下使用脉冲激光光解产生和通过吸收光谱法在时间分辨上检测BrO自由基来检查反应BrO + DMS→产物（1）的动力学。 1托= 133.322帕）。与295 K时的压力无关，获得k_1 =（4.40 +-0.66）* 10〜（-13）cm〜3 s〜（-1）的值。此值明显高于先前在低压下确定的值（ <4 Torr He），流量测量（2.6 * 10〜（-13）cm〜3 s〜（-1））。通过直接观察DMSO的形成，我们在反应1中的产率为1.17±0.34。主要不确定性是DMSO横截面的±30％。使用化学盒模型评估了这些结果对偏远海洋边界层化学性质的影响。在白天浓度为1-2 pmol / mol时，发现BrO自由基是DMS的重要吸收剂和DMSO的主要来源。在第二组实验中，采用脉冲激光光解结合Br原子的共振荧光检测来研究Br + DMS + M可逆Br-DMS + M（4，-4）在100 Torr N_2和295时的平衡动力学。 K. k_4的值=（6.36 +-0.43）* 10〜（-11）cm〜3 s〜（-1）和k _（-4）=（1.02 +-0.07）* 10〜4 s〜（-1 ），并用来计算平衡常数K_4 =（6.24 +-0.56）* 10〜（-15）cm〜3。不确定度为2＃sigma＃加上估计的系统误差。在[Br]高（（1-3）* 10〜（12）cm〜（-3））时，Br原子通过快速反应Br + Br-DMS-> Br_2 + DMS（5）从平衡中丢失，并且得出k_5 =（4.2 _（-1.2）〜（+2.3）* 10〜（-10）cm〜3 s〜（-1）的值，不确定度为2＃sigma＃加上由测量引起的主要系统误差从激光能量密度测量中估算[Br] _o脉冲激光光解与选定波长处的时间分辨UV吸收以及300-450 nm波长范围内的二极管阵列测量相结合，归因于Br-DMS，在365 nm处有很强的吸收。通过拟合Br-DMS产生的时间分辨吸收信号，获得#sigma #_（-1.1）〜（+1.6）* 10〜（-17）cm〜2的值，不确定度为2＃sigma＃加上系统错误（如上所述）。

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