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Open Access Publications from the University of California

Stimulated X-Ray Emission Spectroscopy in Transition Metal Complexes

  • Author(s): Kroll, T
  • Weninger, C
  • Alonso-Mori, R
  • Sokaras, D
  • Zhu, D
  • Mercadier, L
  • Majety, VP
  • Marinelli, A
  • Lutman, A
  • Guetg, MW
  • Decker, FJ
  • Boutet, S
  • Aquila, A
  • Koglin, J
  • Koralek, J
  • Deponte, DP
  • Kern, J
  • Fuller, FD
  • Pastor, E
  • Fransson, T
  • Zhang, Y
  • Yano, J
  • Yachandra, VK
  • Rohringer, N
  • Bergmann, U
  • et al.

© 2018 American Physical Society. We report the observation and analysis of the gain curve of amplified Kα x-ray emission from solutions of Mn(II) and Mn(VII) complexes using an x-ray free electron laser to create the 1s core-hole population inversion. We find spectra at amplification levels extending over 4 orders of magnitude until saturation. We observe bandwidths below the Mn 1s core-hole lifetime broadening in the onset of the stimulated emission. In the exponential amplification regime the resolution corrected spectral width of ∼1.7 eV FWHM is constant over 3 orders of magnitude, pointing to the buildup of transform limited pulses of ∼1 fs duration. Driving the amplification into saturation leads to broadening and a shift of the line. Importantly, the chemical sensitivity of the stimulated x-ray emission to the Mn oxidation state is preserved at power densities of ∼1020 W/cm2 for the incoming x-ray pulses. Differences in signal sensitivity and spectral information compared to conventional (spontaneous) x-ray emission spectroscopy are discussed. Our findings build a baseline for nonlinear x-ray spectroscopy for a wide range of transition metal complexes in inorganic chemistry, catalysis, and materials science.

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