Hydrogen atom catalyzed ortho-to-para conversion in solid molecular hydrogen
Hydrogen atom catalyzed ortho-to-para conversion in solid molecular hydrogen
复制标题
氢原子催化固体分子氢中的邻位至对位转化
DOI：
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
David T. Anderson
中科院分区：
文献类型：
--
作者：
A. Strom;K. Fillmore;David T. Anderson
用红外光谱法研究了掺杂少量氢原子（10-50 ppm）杂质的固体氢样品中分子氢邻位到帕拉（o/p）的转化过程。使用原位193 nm的N2 O掺杂剂分子的光解产生的H-原子。对于具有相对低的初始邻位H2分数（Xo ≤ 0.03）的氢晶体，在1.8和4.0 K温度下的o/p转化动力学遵循先前为H原子催化的o/p转化建立的动力学方程。测得的原子催化的o/p转换动力学表明H-原子在这些条件下是移动的，与以前的ESR测量一致。有人提出，氢原子扩散的量子隧道机制，被描述为化学扩散。对所测得的o/p转化动力学数据的详细拟合允许提取光解后的初始H原子浓度，假定H原子复合速率常数（H + H → H2）的文献值。所测量的o/p转换动力学显示，所观察到的o/p转换远小于基于先前测量的H原子复合速率常数的预期，因此表明H原子不会随机扩散通过晶体，而是优先在高仲氢含量的区域中扩散。从这项研究中估计的H-原子浓度与以前的ESR测量是一致的，但在冲突与各种掺杂剂，如N2 O的H-原子反应的动力学研究。
Infrared spectroscopy is used to investigate the process of molecular hydrogen ortho-to-para (o/p) conversion in solid hydrogen samples doped with small concentrations (10–50 ppm) of hydrogen atoms (H-atoms) as an impurity. The H-atoms are generated using the in situ 193 nm photolysis of N2O dopant molecules. For hydrogen crystals with relatively low initial ortho-H2 fractions (Xo ≤ 0.03), the o/p conversion kinetics at temperatures of 1.8 and 4.0 K follow kinetic equations developed previously for H-atom catalyzed o/p conversion. The measured atom catalyzed o/p conversion kinetics indicates the H-atoms are mobile under these conditions in agreement with previous ESR measurements. It has been proposed that the H-atoms diffuse by a quantum tunneling mechanism that is described as chemical diffusion. Detailed fits of the measured o/p conversion kinetic data allow the initial H-atom concentration after photolysis to be extracted assuming literature values for the H-atom recombination rate constant (H + H → H2). The measured o/p conversion kinetics show the observed o/p conversion is much less than expected based on the previously measured H-atom recombination rate constant and thus suggest that the H-atoms do not diffuse randomly through the crystal but rather diffuse preferentially in regions of high para-hydrogen content. The estimated H-atom concentrations from this study are consistent with previous ESR measurements but in conflict with kinetic studies of H-atom reactions with various dopants such as N2O.
DOI：
10.1016/j.jqsrt.2013.07.002
发表时间：
2013-11-01
影响因子：
2.3
作者：
Rothman, L. S.;Gordon, I. E.;Wagner, G.
通讯作者：
Wagner, G.