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Basic studies toward ultrafast soft x-ray photoelectron diffraction; its application to probing local structure in
T Teramoto1, S Minemoto2, T Majima3
1Institute for Radiation Sciences, Osaka University, 1-1 Machikaneyama-cho, Toyonaka, Osaka 560-0043, Japan.
Structural Dynamics (Melville, N.Y.)
|May 2, 2022
Summary
Ultrafast X-ray photoelectron diffraction (UXPD) using a free-electron laser can probe molecular structure. Initial state degeneracies limit sensitivity, but using nondegenerate orbitals could reveal fine structures.
Area of Science:
- Atomic and Molecular Physics
- Chemical Physics
- Materials Science
Background:
- Ultrafast X-ray Photoelectron Diffraction (UXPD) offers element-specific molecular structure probing.
- Current UXPD schemes involve laser alignment, photoexcitation, and X-ray probing.
Purpose of the Study:
- To investigate the feasibility of UXPD for determining the C-I bond distance in iodobenzene.
- To understand the influence of initial state degeneracies on UXPD sensitivity.
- To establish criteria for successful UXPD experiments.
Main Methods:
- A three-step UXPD scheme using near-infrared laser alignment, UV laser pumping, and soft X-ray Free-Electron Laser (SXFEL) probing.
- Measurement of I 3d XPD profiles from aligned iodobenzene.
- Density Functional Theory (DFT) calculations of I 3d XPD profiles, considering molecular alignment degrees.
Main Results:
- Experimental and theoretical I 3d XPD profiles from iodobenzene were obtained.
- The C-I bond distance could not be precisely determined due to limitations.
- Initial state degeneracies were found to reduce sensitivity to molecular structure in I 3d XPD profiles.
Conclusions:
- UXPD sensitivity to molecular structure is diminished by initial state degeneracies.
- Selecting nondegenerate molecular orbitals for photoemission is crucial for observing fine structures in XPD profiles.
- Key criteria for successful UXPD include using SXFEL, achieving high molecular alignment (>0.8), and probing nondegenerate orbitals.
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