Solution phase high repetition rate laser pump x-ray probe picosecond hard x-ray spectroscopy at the Stanford Synchrotron Radiation Lightsource

• Published in: Structural dynamics (Melville, N.Y.) N.Y.), 2023-09, Vol.10 (5), p.054304-054304
• Main Authors: Reinhard, Marco, Skoien, Dean, Spies, Jacob A., Garcia-Esparza, Angel T., Matson, Benjamin D., Corbett, Jeff, Tian, Kai, Safranek, James, Granados, Eduardo, Strader, Matthew, Gaffney, Kelly J., Alonso-Mori, Roberto, Kroll, Thomas, Sokaras, Dimosthenis
• Format: Article
• Language: English
• Subjects: Absorption spectroscopy; Availability; Camshafts; chemical processes; Data acquisition; Density functional theory; Doped fibers; Electron spin; Electrons; Emission spectra; Energy; Experiments; Fiber lasers; Lasers; Ligands; OTHER INSTRUMENTATION; Phase transitions; Radiation; Repetition; Signal to noise ratio; Spectrum analysis; storage rings; Synchrotron radiation; Synchrotrons; Time measurement; X ray absorption; X ray detectors; x-ray absorption spectroscopy; x-ray emission spectroscopy; X-ray spectroscopy; X-rays; Ytterbium
• ISSN: 2329-7778; 2329-7778
• DOI: 10.1063/4.0000207

We present a dedicated end-station for solution phase high repetition rate (MHz) picosecond hard x-ray spectroscopy at beamline 15-2 of the Stanford Synchrotron Radiation Lightsource. A high-power ultrafast ytterbium-doped fiber laser is used to photoexcite the samples at a repetition rate of 640 kHz, while the data acquisition operates at the 1.28 MHz repetition rate of the storage ring recording data in an alternating on-off mode. The time-resolved x-ray measurements are enabled via gating the x-ray detectors with the 20 mA/70 ps camshaft bunch of SPEAR3, a mode available during the routine operations of the Stanford Synchrotron Radiation Lightsource. As a benchmark study, aiming to demonstrate the advantageous capabilities of this end-station, we have conducted picosecond Fe K-edge x-ray absorption spectroscopy on aqueous [FeII(phen)3]2+, a prototypical spin crossover complex that undergoes light-induced excited spin state trapping forming an electronic excited state with a 0.6–0.7 ns lifetime. In addition, we report transient Fe Kβ main line and valence-to-core x-ray emission spectra, showing a unique detection sensitivity and an excellent agreement with model spectra and density functional theory calculations, respectively. Notably, the achieved signal-to-noise ratio, the overall performance, and the routine availability of the developed end-station have enabled a systematic time-resolved science program using the monochromatic beam at the Stanford Synchrotron Radiation Lightsource.