Institut für Nukleare Entsorgung (INE)

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