Study and control of Rydberg-molecule interactions with surfaces and adsorbates

当一个分子吸收深紫外辐射时，它可能会以里德伯态的形式短暂存在，在这种状态下，一个电子被提升到离分子核心很远的高能轨道上。在这种状态下，分子具有奇异的性质，因为受激的里德伯电子很容易受到外部电场或磁场以及与其他分子的相互作用的干扰。这个提议是关于研究当这些里德伯分子在气相中由激光激发产生碰撞到固体表面时发生的新的化学和物理现象。从广义上讲，气相分子和固体表面之间的碰撞在从催化、腐蚀、电子设备技术到平流层臭氧空洞的形成等广泛的化学过程中都很重要。一种称为等离子体的气相环境是由带电（电离）物质、高活性自由基和电子激发的富含能量物质（包括里德伯原子和分子）的混合物组成的。等离子体沉积过程在电子工业中具有重要意义，而气相等离子体和固体表面之间的相互作用是该过程的核心。里德伯原子和分子在等离子体中的作用尚不清楚。在这里提出的工作中，我们的目标是在基本水平上理解亚稳态里德伯分子和定义良好的表面之间的相互作用。我们将瞄准一束分子，这些分子被激光激发成里德伯态，在一个明确定义和特征的表面上，研究发生的过程。这些将包括：通过电子转移到表面的影响分子的电离；通过化学键断裂使进入的分子解离；里德堡电子的能量沉积到表面以打破键并引发与表面结合的吸附剂的化学过程。我们将研究是否有可能使用外加电场来控制这些过程的倾向。里德伯电子的轨道可以被这些场严重扭曲，这影响了随后的化学行为，并可能对其与表面的相互作用产生深远的影响。

When a molecule absorbs deep ultraviolet radiation it may exist transiently as a Rydberg state in which one of the electrons has been promoted into a high-energy orbit at a long distance from the core of the molecule. In such states, molecules have exotic properties because the excited Rydberg electron is very easily perturbed by external electric or magnetic fields and by interactions with other molecules. This proposal is concerned with the investigation of the novel chemistry and physics that occurs when these Rydberg molecules, created by laser excitation in the gas phase, bump into a solid surface. In broad terms, collisions between molecules in the gas phase and solid surfaces are of importance in a wide range of chemical processes ranging from catalysis, to corrosion, to electronic device technology to the formation of the ozone hole in the stratosphere. One type of gas phase environment, known as a plasma , is made up of a mixture of charged (ionized) species, highly reactive free radicals, and electronically-excited energy-rich species including Rydberg atoms and molecules. The process of plasma deposition is of major importance in the electronics industry and the interaction between the gas-phase plasma and solid surfaces lies at the heart of this process. The role of Rydberg atoms and molecules in plasmas is poorly understood. In the work proposed here, we aim to understand at a fundamental level the interaction between the metastable Rydberg molecules and well-defined surfaces. We will target a beam of molecules, which have been laser excited into Rydberg states, at a well defined and characterised surface and study the processes that occur. These will include: ionization of the impacting molecules by electron transfer to the surface; dissociation of the incoming molecules via chemical bond breaking; deposition of the energy of the Rydberg electron into the surface to break bonds and initiate chemical processes of adsorbates bonded to the surface. We will investigate whether it is possible to control the propensities for these processes using applied electric fields. The orbit of the Rydberg electron can be severely distorted by such fields and this affects the subsequent chemical behaviour and may have a profound effect on its interaction with the surface.