MuSR and muonium studies of chemical reactivity and molecular interactions (at TRIUMF)

MuSR 和 μ 化学反应性和分子相互作用的研究（TRIUMF）

• 批准号: 43731-2006
• 负责人: Fleming, Donald
• 金额: $ 3.64万
• 依托单位: TRIUMF
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2008
• 资助国家: 加拿大
• 起止时间: 2008-01-01 至 2009-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=390524
• 关键词: MuSR; muonium; studies; chemical; reactivity

From a nuclear/physical chemistry perspective, the positive muon and its muonium atom (Mu=u+e-) is endowed with two key aspects: (i) the muon polarization in its environment, initally 100%, which can be sensitively monitored and (ii) the mass of the Mu atom, which is 1/9th that of the H-atom (but otherwise chemically identical), thereby providing for unique tests of quantum mass effects in chemical reactivity. The first aspect finds expression in the use of the muon as a spin probe of the molecular interactions and hyperfine coupling constants of muoniated free radicals in the catalytic environments of zeolites. The proposed research is to study both aryl (eg., substituted cyclohexadieynl) and alkyl (eg., from cis-2-butene, or the Mu-t-butyl radical) muoniated radicals in faujasites , above RT, in order to explore temperatures of catalytic interest. There are little or no ESR studies of H-adduct radicals which could be formed from acidic zeolites (HY)  and which could thereby act as reactive intermediates in these important industrial catalysts. The second aspect finds expression in the measurement of chemical reaction rates of the  light H-atom isotope, muonium. Despite the importance  of measured single-collision reaction rates in the field of chemical reaction dynamics, it is still bulk rate constants that impact on both life processes and industrial chemistry. Moreover, from a scientific perspective, the continued measurement of bulk rate constants often provides the best tests of the nature of the underlying Potential Energy Surface, in which quantum mass effects, notably tunelling and Zero Point Energy shifts are probed near threshold, and most dramatically so for the Mu atom. Current research in our group is focussed on the study of recombination rates with small molecules of interest to both theoretical and atmospheric chemistry (CO, NO, N2O,CO2, NO2) over wide ranges of pressure and temperature, including studies in supercritical CO2.  In these endeavours the ultra-light muon mass plays a pivotal role, affecting the reaction rates for addition, dissociation and stabilization in a synergistic way.

从核/物理化学的角度来看，正Muon及其Muon原子(Mu=u+e-)具有两个关键方面：(I)其环境中的Muon极化，最初为100%，可被灵敏地监测；(Ii)Mu原子的质量，其质量是H原子的1/9(但其他化学上相同)，从而提供了对化学反应中量子质量效应的独特测试。第一个方面表现在使用介子作为分子相互作用的自旋探针和分子筛催化环境中的超精细耦合常数。建议的研究是研究八面沸石中芳基(例如，取代的环己二烯)和烷基(例如，来自顺-2-丁烯或Mu-叔丁基自由基)的相互作用的自由基，以探索催化感兴趣的温度。几乎没有关于H-加合物自由基的ESR研究，这些自由基可以从酸性沸石(HY)中形成，从而在这些重要的工业催化剂中充当活性中间体。第二个方面体现在对最轻的氢原子同位素--钚的化学反应速率的测量上。尽管测量的单碰撞反应速率在化学反应动力学领域具有重要意义，但对生命过程和工业化学都有影响的仍然是体积速率常数。此外，从科学的角度来看，对体积速率常数的持续测量往往提供了对潜在势能面性质的最佳测试，其中量子质量效应，特别是调谐和零点能量移动被探测到接近阈值，最戏剧性的是对Mu原子如此。我们小组目前的研究集中在理论和大气化学(CO、NO、N2O、CO2、NO2)在广泛的压力和温度范围内与小分子的复合速率的研究，包括超临界CO2的研究。在这些努力中，超轻介子质量起着关键作用，以协同的方式影响加成、解离和稳定的反应速率。