Advanced x-ray spectroscopy of actinide trichlorides

Area of Science:

• Nuclear Chemistry and Physics
• Materials Science
• Spectroscopy

Background:

• Actinide M4,5 edges are sensitive probes of electronic structure.
• Conventional X-ray absorption spectroscopy (XAS) provides insights into chemical states.
• Resonant inelastic x-ray scattering (RIXS) and HERFD-XAS offer enhanced sensitivity.

Purpose of the Study:

• To analyze the application of core-to-core (3d-to-4f) RIXS and HERFD-XAS at actinide M4,5 edges.
• To evaluate the sensitivity of these techniques to chemical state changes in trivalent actinide compounds.
• To investigate the relationship between HERFD-XAS and conventional XAS methods.

Main Methods:

• Utilized crystal-field multiplet formalism to calculate 3d-4f RIXS maps for actinide chlorides (AnCl3).
• Extracted HERFD-XAS spectra as cuts from RIXS maps at the An M4,5 edges.
• Employed a point-charge electrostatic model to study spectral dependence on coordination number.

Main Results:

• HERFD-XAS at the An M5 edge can monitor small variations in the actinide chemical state, despite spectral profile differences from conventional XAS.
• Better agreement between HERFD-XAS and XAS spectra was observed for An M4 edges compared to M5 edges.
• Calculations revealed significant sensitivity of An 5f state distribution to ligand structural arrangement around actinide sites.

Conclusions:

• Core-to-core RIXS and HERFD-XAS are powerful tools for characterizing trivalent actinides.
• HERFD-XAS demonstrates high potential for probing subtle changes in actinide chemical states and coordination environments.
• These advanced spectroscopic methods provide detailed insights into the electronic structure of actinides.