Muons as Sensitive Isotopic H-atom Probes of Quantum Mass Effects in Chemical Reactivity and of the Motion of Muoniated Free Radicals in Nanoparticle Environments.

μ 子作为化学反应中量子质量效应和纳米颗粒环境中 μ 化自由基运动的敏感同位素氢原子探针。

• 批准号: 43731-2012
• 负责人: Fleming, Donald
• 金额: $ 2.55万
• 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: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=650838
• 关键词: Muons; Sensitive; Isotopic; atom; Probes

The study of chemical reaction rates is central to the whole field of chemistry and in this study it is often **the most simple elementary steps in a complex mechanism that are the most important. Chief among these **are the reaction rates of the H-atom and its isotopic variants; deuterium (D), with a mass of 2 amu, being **the most well known. Isotopes have the same number of electrons but different nuclear masses. Another **common hydrogen isotope is tritium (T), with a mass of 3 amu, but being dangerously radioactive, it has **seen little use in the study of thermal reaction rates. Thus it has fallen to nuclear science and particularly **muon science to extend the isotopic H-atom mass scale. The lightest isotope of the H-atom is Muonium **(Mu= u+e-), where `u+' is a positive muon, with a mass only 1/9th that of the proton. Though lacking a **"nucleus'' in the conventional sense, the muon mass is still 200 times the electron mass, meaning that **Mu and H atoms exhibit the same chemistry, but with very different reaction rates due to their factor of **nine difference in mass. This application is concerned with new directions in Mu reactivity from state-**selected reactants, using lasers to populate molecular excited states. At the other end of the mass scale **is the Muonic He atom (4Heu), where negative muons from the TRIUMF accelerator are captured by a **Helium atom, replacing one electron in the process, thereby endowing 4Heu with a mass of 4.1 amu, the **heaviest isotope of the H-atom. We are now in a position to compare the reaction rates of Mu and 4Heu **over an unprecedented ratio of a factor of 36 in mass, also a key aspect of the present application. A **possible practical aspect of our study of Mu reactivity is the formation of ''muoniated radicals'' and in **particular their motional effects in important industrial catalysts like Zeolites, for which there is no other **technique that can yield the same detailed results. This too is an important aspect of the present application,**but extended to other environments, the study of muoniated radicals on Au nanoparticles.************

化学反应速率的研究是整个化学领域的核心，在这项研究中，复杂机制中最简单的基本步骤往往是最重要的。其中最主要的是h原子及其同位素变体的反应速率；质量为2amu的氘(D)是最著名的。同位素的电子数相同，但原子核质量不同。另一种常见的氢同位素是氚(T)，质量为3amu，但由于具有危险的放射性，它在热反应速率的研究中几乎没有应用。因此，扩展同位素h原子质量尺度的工作就落到了核科学，特别是μ子科学的肩上。氢原子最轻的同位素是μ子（Mu= u+e-），其中“u+”是一个正的μ子，质量仅为质子的1/9。虽然没有传统意义上的“原子核”，但μ子的质量仍然是电子质量的200倍，这意味着**Mu原子和H原子表现出相同的化学性质，但由于它们的质量差** 9，它们的反应速率非常不同。这一应用涉及到用激光填充分子激发态从状态选择的反应物中研究Mu反应性的新方向。在质量尺度的另一端是μ子He原子（4Heu），来自TRIUMF加速器的负μ子被氦原子捕获，在这个过程中取代了一个电子，从而赋予4Heu 4.1 amu的质量，这是h原子最重的同位素。我们现在可以比较Mu和4Heu **的反应速率，这是前所未有的质量比为36倍，这也是目前应用的一个关键方面。我们研究Mu反应性的一个可能的实际方面是“钝化自由基”的形成，特别是它们在沸石等重要工业催化剂中的运动效应，没有其他技术可以产生同样详细的结果。这也是目前应用的一个重要方面，**但扩展到其他环境，研究Au纳米粒子上的电离自由基。************