X-ray absorption spectroscopy using a self-seeded soft X-ray free-electron laser

Area of Science:

• Atomic and Molecular Physics
• Materials Science
• Spectroscopy

Background:

• X-ray free electron lasers (XFELs) offer novel capabilities for investigating transition metal electronic structures and dynamics.
• L-edge absorption spectroscopy (XAS) is a key technique, but its application at XFELs requires narrower x-ray bandwidth than typically provided by self-amplified spontaneous emission (SASE).
• Existing methods necessitate additional monochromatization, complicating experiments.

Purpose of the Study:

• To compare the efficacy of monochromatizing self-amplified spontaneous emission (SASE) radiation versus a novel self-seeding technique at the Linac Coherent Light Source (LCLS) for L-edge XAS.
• To demonstrate the feasibility of performing L-edge XAS using LCLS self-seeding without external monochromators.
• To investigate the influence of undulator configurations on spectral shape and pulse energy for XAS measurements.

Main Methods:

• Comparison of L-edge XAS on a model transition metal system using two XFEL radiation modes: SASE with external monochromatization and self-seeded LCLS radiation.
• Characterization of spectral properties and pulse energy of the self-seeding scheme under varying undulator parameters.
• Analysis of the impact of these parameters on the resulting XAS measurements.

Main Results:

• L-edge XAS can be successfully performed using the LCLS self-seeding scheme, eliminating the need for an additional beamline monochromator.
• The spectral shape and pulse energy of the self-seeding radiation are tunable via the undulator setup.
• These tunable properties directly influence the quality and outcome of the x-ray spectroscopy measurements.

Conclusions:

• The self-seeding technique provides a more streamlined approach for L-edge XAS at XFELs.
• This method enhances the study of electronic structure and dynamics in transition metal systems.
• Optimizing undulator parameters in the self-seeding scheme is crucial for effective XAS experiments.