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发挥着关键作用，从恒星的形成到火箭燃料的安全存储，到氢燃料电池和工业催化。尽管它也是现存的最简单的分子，但我们还没有对氢与最简单的固体表面的相互作用有一个准确的预测理解。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索氢与表面的碰撞。有几个因素可以决定这些碰撞的结果，包括分子移动的速度有多快，它相对于表面的旋转方式，以及构成表面的材料和表面温度。可以独立改变这些(和其他)因素中的每一个的实验将提供对这种气体-表面碰撞的最详细的洞察，因为他们探索每个因素所起的作用，消除平均的需要和由此导致的不确定性，并提供必须准确地再现这些精心控制的实验的最严格的理论模型测试。在这个项目中，氢分子的旋转方向将被控制和操纵，以确定该参数是否可以用于控制氢分子在与表面碰撞中的反应性。这些测量将使用一种独特而新颖的磁操纵实验仪器和技术进行，该仪器和技术设在斯旺西大学化学系，用于在散射实验中控制氢分子的旋转方向。这些实验的结果将提供第一个定量的洞察力，以了解氢的旋转方向对分子与表面碰撞时解离概率的影响。该项目还将探索氢的旋转取向如何改变分子和表面之间的能量转移。这一能量转移过程是将分子捕获到表面并相应改变反应几率的重要步骤，但它与分子旋转方向的关系迄今尚不为以往的实验所能获得。最后，在建立了氢原子碰撞的方法之后，将进一步开发用于甲烷等小多原子分子的设备和技术。所有项目的结果对于开发准确的气体-表面反应理论模型将是无价的。

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.