Non-Thermal Reactions in Thin Aqueous Films
EMSL Project ID
24799
Abstract
This proposal is a continuation of research under EMSL User Proposal #21797. Energetic processes at surfaces and interfaces are important in fields such as radiation chemistry, radiation biology, waste processing, and advanced materials synthesis. Low-energy electrons (<100 eV) frequently play a dominant role in these energetic processes since the higher energy primary particles produce numerous low-energy, chemically active, secondary electrons. In addition, the presence of surfaces or interfaces modifies the physics and chemistry compared to what occurs in the bulk. We will use electron-stimulated desorption, temperature programmed desorption, Fourier transform infrared spectroscopy, and other ultra-high vacuum (UHV) surface science techniques to investigate energetic, electron-stimulated reactions at surfaces and interfaces, and in thin aqueous films. A key element of the approach is to use a tunable, mono-energetic electron beam and precisely tailored model systems to unravel the complex chemistry that results from the simultaneous release of electrons with a broad range of energies by the primary excitation events associated with ionizing radiation. This work addresses several important issues, including understanding the relative importance of the primary excitation source compared to the secondary electrons it produces, energy transfer at surfaces and interfaces, and new reaction pathways at surfaces. Specifically, these studies are designed to address the following key scientific issues. How does interface between the water film and the substrate influence the energy deposition (by, for example, altering electron-ion recombination) and subsequent reactions? What are the mechanisms responsible for the transport/migration/diffusion of chemically reactive species in irradiated ASW films? How does the presence of solutes influence the energy deposition in aqueous films and the subsequent non-thermal chemistry? What are the lifetimes of electronically excited water molecules, and how far can they diffuse?
Project Details
Project type
Large-Scale EMSL Research
Start Date
2007-05-31
End Date
2010-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
45) Nikolay G. Petrik and Greg A. Kimmel, “Hydrogen bonding, H/D exchange and molecular mobility in thin water films on TiO2(110),” Phys. Rev. Lett. 99, 196103 (2007).
Akin MC, NG Petrik, and GA Kimmel. 2009. "Electron-Stimulated Reactions and O-2 Production in Methanol-Covered Amorphous Solid Water Films." Journal of Chemical Physics 130(10):Art. No. 104710.
Kimmel GA, J Matthiesen, M Baer, CJ Mundy, NG Petrik, RS Smith, Z Dohnalek, and BD Kay. 2009. "No Confinement Needed: Observation of a Metastable Hydrophobic Wetting Two-Layer Ice on Graphene." Journal of the American Chemical Society 131(35):12838-12844.
Petrik NG, and GA Kimmel. 2009. "Nonthermal Water Splitting on Rutile TiO2: Electron-Stimulated Production of H-2 and O-2 in Amorphous Solid Water Films on TiO2(110)." Journal of Physical Chemistry C 113(11):4451-4460.
Petrik NG, and GA Kimmel. 2011. "Electron- and hole-mediated reactions in UV -irradiated O2 adsorbed on reduced rutile TiO2(110)." Journal of Physical Chemistry C 115(1):152-164. doi:10.1021/jp108909p
Petrik NG, Z Zhang, Y Du, Z Dohnalek, I Lyubinetsky, and GA Kimmel. 2009. "Chemical Reactivity of Reduced TiO2(110): The dominant role of surface defects in oxygen chemisorption." Journal of Physical Chemistry C 113(28):12407-12411. doi:10.1021/jp901989x