Seeded stimulated X-ray emission at 5.9 keV
Margaret Doyle, Aliaksei Halavanau, Yu Zhang, Yurina Michine, Joshua Everts, Franklin D. Fuller, Roberto Alonso‐Mori, Makina Yabashi, Ichiro Inoue, Taito Osaka, Jumpei Yamada, Yuichi Inubushi, Toru Hara, Jan Kern, Junko Yano, Vittal K. Yachandra, Nina Rohringer, Hitoki Yoneda, Thomas Kröll, Claudio Pellegrini, Uwe Bergmann
Abstract
X-ray free-electron lasers (XFELs) provide intense pulses that can generate stimulated X-ray emission, a phenomenon that has been observed and studied in materials ranging from neon to copper. Two schemes have been employed: amplified spontaneous emission (ASE) and seeded stimulated emission (SSE), where a second color XFEL pulse provides the seed. Both phenomena are currently explored for coherent X-ray laser sources and spectroscopy. Here, we report measurements of ASE and SSE of the 5.9 keV Mn K α 1 fluorescence line from a 3.9 molar NaMnO 4 solution, pumped with 7 femtosecond FWHM XFEL pulses at 6.6 keV. We observed ASE at a pump pulse intensity of 1.7×10 19 W/cm 2 , consistent with earlier findings. We observed SSE at dramatically reduced pump pulse intensities down to 1.1×10 17 W/cm 2 . These intensities are well within the range of many existing XFEL instruments, which supports the experimental feasibility of SSE as a tool to generate coherent X-ray pulses, spectroscopic studies of transition metal complexes, and other applications.