2021 Fiscal Year Research-status Report
Electron Scattering and Electron Angular Anisotropy in Water and Aqueous Solution
| Project/Area Number |
20K15229
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| Research Institution | Kyoto University |
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Principal Investigator |
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| Project Period (FY) |
2020-04-01 – 2023-03-31
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| Keywords | electron spectroscopy / electron scattering / liquid water / photoelectron anisotropy |
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| Outline of Annual Research Achievements |
The project studies electron scattering and its impact on electron angular distributions in liquids using photoelectron spectroscopy in international collaboration. Electron scattering is crucial for understanding energy deposition, radical formation and biological damage by slow and fast electrons, and a correct interpretation of spectra from liquid water and aqueous solutions.
A novel energy-referencing scheme has been developed to determine accurate ionization energies from aqueous solutions down to a few-10 meV scale. This enables the study of surface-specific effects as well as detection of even small energy shifted due to inelastic electron scattering.
This novel method was then applied to solutions of sodium iodide and tetrabutylammonium iodide, which showed very different concentration-dependent energy shifts. The former is a model system for bulk electronic structure changes while the latter is a surface-active species, which modifies the surface potential of the solution.
Knowledge of electron scattering behavior at low kinetic energies was used to interpret the very first photoelectron circular dichroism from liquid fenchone, a chiral molecule. After careful subtraction of the scattering background signal a significant left / right asymmetry was found. This first result opens the path for studies of biologically relevant molecules in aqueous solutions.
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| Current Status of Research Progress |
Current Status of Research Progress
1: Research has progressed more than it was originally planned.
Reason
Even though the pandemic is still ongoing, effective online collaboration and work sharing with international partners have resulted in good progress of the project. Experimental measurements are ongoing in Germany, while analysis is conducted in Japan. Several topics are already in the wrap-up phase on the way to publishing results while experiments continue in parallel.
The new absolute-energy referencing method developed last year in combination with gained knowledge on electron scattering behavior at low kinetic energies proved to be a crucial basis to study photoemission from a flat jet as well as from chiral molecules, both emerging new fields in liquid-jet spectroscopy.
Overall, the project is progressing smoothly and already more difficult-to-interpret solutes are being studied.
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| Strategy for Future Research Activity |
While the pandemic situation is slowly relaxing, the collaboration will continue online for the time being. Plans to resume travel for a more direct collaboration and on-site experiments in Germany are underway.
After establishing accurate binding-energy measurements the next goal is to access energies referenced to the Fermi-level (or electrochemical potential), which will make it possible to discern surface- or bulk specific effects of solutes. This promises to open the pathway for quantifying probing depth and a solution's surface potential. In parallel, measurements of calibrated liquid-phase spectra will be undertaken, which are then compared with a physical scattering model to gain insight into then relative probability of electron scattering at different energies.
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| Causes of Carryover |
The project proposed international collaboration with mainly business travel expenses to join experiments in Europe and discuss with collaboration partners directly. This has unfortunately been made impossible by the ongoing corona pandemic. Thanks to effective online collaboration the research project is not negatively impacted by this. Travel will be resumed for a more effective collaboration as soon as the travel restrictions have been lifted. If possible the expenses will be used for 2-3 business trips to Europe and travel to conferences as originally planned in the proposal.
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