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Chemie / Physik / Spektroskopie

Chemie / Physik / Spektroskopie
Forschungsthema:Synchrotron beam induced speciation changes in XAFS studies of aquatic radionuclide systems
Typ:Masterarbeit
Datum:Ab Jan. 2020
Betreuer:

Prof. Dr. Horst Geckeis
Dr. Jörg Rothe
Dr. Kathy Dardenne

Links:Ausschreibung

Work description

For some selected aqueous systems (e.g., the Neptunium(IV) aquo-ion Np(IV)aq, which tends to be oxidized to the trans-dioxo Np(V)O2+ cation in the presence of an intense synchrotron X-ray beam), beam induced speciation changes will be investigated by controlling and systematically changing the relevant experimental parameters:

  • Metal cation concentration
  • Total photon flux
  • Photon flux density (focused/defocused beam)
  • Sample temperature (from room to liquid nitrogen temperature)
  • Exposure time to the beam
  • Ground state electronic level (K- vs. L- / L- vs. M-edge)
  • Conditions for recovery of the pristine state before irradiation

These investigations will include a precise determination of the beam induced temperature increase (deposited energy) in the sample vial (“beam damage” might be actually a temperature induced speciation change) as well as EXAFS studies of the effect of deep freezing on the “aqueous” speciation.

 

Methods:

  • XAFS spectroscopy at well-defined conditions in transmission / fluorescence detection mode at the INE and ACT beamline stations (coop. INE beamline group)
  • Sample preparation (coop. INE aquatic chemistry group)
  • XAFS data analysis  

 

More details