Rotationally controlled gas-surface reactions

氢（H2）是宇宙中最丰富的分子，它与表面的相互作用在许多应用中起着关键作用，从恒星的形成和火箭燃料的安全储存，到氢燃料电池和工业催化。尽管H2也是存在的最简单的分子，但我们对H2与最简单的固体表面的相互作用还没有准确的预测性理解。因此，为了提高我们的知识和理解，需要仔细控制实验，在基本的分子水平上探测H2与表面的碰撞。有几个因素可以决定这些碰撞的结果，包括分子的运动速度和相对于表面的旋转方式，以及表面的材料和表面温度。实验可以独立地改变每一个这些（和其他）因素将提供对这种气体-表面碰撞的最详细的洞察，因为它们探测每个因素所起的作用，消除了平均的需要和由此导致的不确定性，并提供了对理论模型的最严格的测试，这些理论模型必须准确地再现这些精心控制的实验。在这个项目中，氢分子的旋转取向，其可被认为对应于分子是像直升机还是侧手翻一样旋转，将被控制和操纵以确定该参数是否可用于控制H2与表面碰撞的反应性。这些测量将使用一种独特的和新颖的磁操纵实验装置和技术进行，该装置和技术位于斯旺西大学化学系内，以控制散射实验中H2分子的旋转取向。这些实验的结果将提供第一个定量的洞察力的影响的旋转取向的H2分子解离的概率，当它与表面碰撞。该项目还将探索H2的旋转方向如何改变分子和表面之间的能量转移。这种能量转移过程是将分子捕获在表面上的重要步骤，并相应地改变反应概率，但它与分子旋转取向的关系迄今为止还无法通过以前的实验获得。最后，在建立了H2碰撞的方法之后，将进一步开发用于甲烷等小多原子分子的装置和技术。所有项目的结果将是无价的，在寻求发展准确的理论模型的气体表面反应。

Hydrogen (H2) is the most abundant molecule in the universe, and its interaction with surfaces plays a pivotal role in many applications, from the formation of stars and the safe storage of rocket fuel, to hydrogen fuel cells and industrial catalysis. Despite also being the simplest molecule in existence, we do not yet have an accurate predictive understanding of the interaction of H2 with even the simplest solid surfaces. As such, to improve our knowledge and understanding, carefully controlled experiments are required which probe the collisions of H2 with surfaces at a fundamental, molecular level. There are several factors that can determine the outcome of these collisions, including how fast the molecule is travelling and how it is rotating with respect to the surface, as well as the material the surface is made from and the surface temperature. Experiments which can independently vary each of these (and other) factors will provide the most detailed insight into this gas-surface collision, as they probe the role each factor plays, remove the need for averaging and the uncertainty this leads to, and provide the most stringent tests of theoretical models that must accurately reproduce these carefully controlled experiments.In this project the rotational orientation of hydrogen molecules, which can be considered to correspond to whether the molecule is rotating like a helicopter or a cartwheel, will be controlled and manipulated to determine whether this parameter can be used to control the reactivity of H2 in collisions with a surface. These measurements will be performed using a unique and novel magnetic manipulation experimental apparatus and technique, that is based within the Department of Chemistry at Swansea University, to control the rotational orientation of H2 molecules in scattering experiments. The results of these experiments will provide the first quantitative insight into the effect the rotational orientation of H2 has on the probability the molecule dissociates when it collides with a surface. The project will also explore how the rotational orientation of H2 changes the transfer of energy between the molecule and the surface. This energy transfer process is an important step for trapping a molecule on a surface and correspondingly changes reaction probabilities, yet its relation to the rotational orientation of the molecule was so far inaccessible to previous experiments. Finally, having established the methodology for collisions on H2, the apparatus and technique will be further developed for small polyatomic molecules such as methane. The results from all of the project will be invaluable in the quest to develop accurate theoretical models of gas-surface reactions.