Kettwich Sharon C, Raston Paul L, Anderson David T
Department of Chemistry, University of Wyoming, Laramie, Wyoming 82071, USA.
J Phys Chem A. 2009 Jul 2;113(26):7621-9. doi: 10.1021/jp811206a.
We report IR + UV coirradiation photolysis experiments conducted on Cl(2)-doped para-hydrogen (p-H(2)) crystals at 1.8 K, using pulsed 355 nm UV radiation and cw broad-band near-IR light from a FTIR tungsten source. The amount of HCl photoproduct is monitored using FTIR spectroscopy as a function of the IR + UV exposure time. Detailed analysis of the HCl growth kinetics reveals that the reaction Cl + H(2)(v=1,J=0) --> HCl + H is playing a significant (15%) role in the in situ photochemistry. In contrast, UV-only photolysis experiments conducted under similar conditions produce almost exclusively (99%) isolated Cl atom photofragments, indicating the reaction Cl + H(2)(v=0,J=0) --> HCl + H is not readily occurring. This combination of photolysis experiments confirms that under these conditions, the Cl + H(2) reaction probability increases by a factor greater than 25 for Cl atom reactions with H(2)(v=1) versus H(2)(v=0). These results are therefore consistent with the expectation that vibrational excitation of the H(2) reagent lowers the reaction threshold and increases the reaction cross section for the Cl + H(2) reaction. These experimental studies were motivated by and are compared to the quantum model simulations reported by Korolkov, Manz, and Schild in the accompanying paper.
我们报告了在1.8 K温度下，对掺杂氯气的对氢（p-H₂）晶体进行红外（IR）+紫外（UV）共辐照光解实验的情况，实验中使用了脉冲355 nm紫外辐射以及来自傅里叶变换红外光谱仪（FTIR）钨光源的连续宽带近红外光。利用傅里叶变换红外光谱仪监测氯化氢光产物的量，并将其作为红外+紫外辐照时间的函数。对氯化氢生长动力学的详细分析表明，反应Cl + H₂(v = 1, J = 0) → HCl + H在原位光化学中起着重要作用（15%）。相比之下，在类似条件下进行的仅紫外光解实验几乎只产生孤立的氯原子光碎片（99%），这表明反应Cl + H₂(v = 0, J = 0) → HCl + H不容易发生。这些光解实验的组合证实，在这些条件下，与H₂(v = 0)相比，氯原子与H₂(v = 1)反应时，Cl + H₂反应概率增加了25倍以上。因此，这些结果与预期一致，即H₂试剂的振动激发降低了反应阈值，并增加了Cl + H₂反应的反应截面。这些实验研究的动机来自于并与随附论文中Korolkov、Manz和Schild报道的量子模型模拟进行了比较。
