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

Lead Research Organisation: University of Oxford
Department Name: Oxford Chemistry

Abstract

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.

Publications

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Gibbard J (2016) Resonant charge transfer of hydrogen Rydberg atoms incident at a metallic sphere in Journal of Physics B: Atomic, Molecular and Optical Physics

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McCormack E (2012) Detection of electrons in the surface ionization of H Rydberg atoms and H 2 Rydberg molecules in Journal of Physics B: Atomic, Molecular and Optical Physics

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McCormack EA (2010) Level crossings in the ionization of H(2) Rydberg molecules at a metal surface. in The journal of physical chemistry. A

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Sashikesh G (2013) Ionization of Rydberg H2 molecules at doped silicon surfaces. in The Journal of chemical physics

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So E (2015) Ionization of Rydberg H atoms at band-gap metal surfaces via surface and image states in Journal of Physics B: Atomic, Molecular and Optical Physics

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So E (2011) Charge transfer of Rydberg H atoms at a metal surface. in Physical review letters

 
Description A range of studies have been conducted involving the interaction of a beam of highly excited (Rydberg) hydrogen atoms with various types of solid surface. These include fully conducting surfaces (e.g., gold), semiconducting surfaces (doped silicon and single crystal copper), thin film surfaces (iron on mica), insulators (mica), and surfaces coated with nanoparticles. The studies reveal the sensitivity of the electron transfer process to the electronic and geometrical properties of the surface
Exploitation Route Possible development of analytical technique to probe surface electronic properties.
Sectors Chemicals,Electronics,Energy

 
Description European Union Framework 7
Amount £4,100,000 (GBP)
Funding ID COHERENCE 
Organisation European Commission 
Department Seventh Framework Programme (FP7)
Sector Public
Country European Union (EU)
Start  
 
Description European Union Framework 7
Amount £124,044 (GBP)
Funding ID RIANS 
Organisation European Commission 
Department Seventh Framework Programme (FP7)
Sector Public
Country European Union (EU)
Start  
 
Description European Union Framework 7
Amount £4,100,000 (GBP)
Funding ID COHERENCE 
Organisation European Commission 
Department Seventh Framework Programme (FP7)
Sector Public
Country European Union (EU)
Start  
 
Description European Union Framework 7
Amount £124,044 (GBP)
Funding ID RIANS 
Organisation European Commission 
Department Seventh Framework Programme (FP7)
Sector Public
Country European Union (EU)
Start