Imaging collisions of OH radicals with liquid surfaces

这是一个化学博士研究项目。气相分子与液体表面的相互作用在许多现实环境中是重要的。他们的研究提出了许多严峻的实验挑战，因为开发可以与液相样品耦合的表面敏感方法存在困难。其中一类重要的反应是大气气溶胶颗粒表面对OH自由基的吸收；这些过程具有重要的气候意义。我们一直在研究OH自由基与液体表面碰撞的基本初级事件，选择它们作为气溶胶表面化学功能的代表。我们扩展了之前的工作，引入了OH自由基的分子束源，并将其与一种新的基于激光的成像方法相结合。这为进行新的动态测量开辟了道路，我们可以获得分散的OH分子的速度和角分布与其内部量子态之间的相关性。观测到的特征高度表明了地表直接碰撞机制和更复杂碰撞机制之间的平衡。这一见解很有价值，无论是在这种特殊情况下，还是在帮助更广泛地了解气液界面化学的一般领域。

This is a PhD research project in Chemistry. The interactions of gas-phase molecules with the surfaces of liquids are important in a number of real-world environments. Their study presents a number of serious experimental challenges, because of the difficulties of developing surface-sensitive methods that can be coupled with liquid-phase samples. One important class of these reactions is the uptake of OH radicals at the surfaces of atmospheric aerosol particles; these processes have important climatic implications. We have been studying the fundamental primary events in the collisions of OH radicals with liquid surfaces chosen as proxies for the chemical functionality present at the surfaces of aerosols. We have extended our previous work by introducing a molecular-beam source of the OH radicals and combining it with a novel, laser-based imaging method. This has opened the way to making new classes of dynamical measurements, where we can obtain the correlations between the speed and angular distributions of the scattered OH molecules and their internal quantum states. The observed characteristics are highly indicative of the balance between competing direct and more-complex collisional mechanisms at the surface. This insight is valuable, both in this particular context and also in helping to inform the general field of gas-liquid interfacial chemistry more widely.