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Stimulated X-ray emission for materials science


Resonant inelastic X-ray scattering and X-ray emission spectroscopy can be used to probe the energy and dispersion of the elementary low-energy excitations that govern functionality in matter: vibronic, charge, spin and orbital excitations1,2,3,4,5,6,7. A key drawback of resonant inelastic X-ray scattering has been the need for high photon densities to compensate for fluorescence yields of less than a per cent for soft X-rays8. Sample damage from the dominant non-radiative decays thus limits the materials to which such techniques can be applied and the spectral resolution that can be obtained. A means of improving the yield is therefore highly desirable. Here we demonstrate stimulated X-ray emission for crystalline silicon at photon densities that are easily achievable with free-electron lasers9. The stimulated radiative decay of core excited species at the expense of non-radiative processes reduces sample damage and permits narrow-bandwidth detection in the directed beam of stimulated radiation. We deduce how stimulated X-ray emission can be enhanced by several orders of magnitude to provide, with high yield and reduced sample damage, a superior probe for low-energy excitations and their dispersion in matter. This is the first step to bringing nonlinear X-ray physics in the condensed phase from theory10,11,12,13,14,15,16 to application.

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Figure 1: Geometry to observe spontaneously stimulated X-ray emission from solids.
Figure 2: Observing stimulated emission from a solid.
Figure 3: Spectrally resolved stimulated emission.


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We thank N. Rohringer, A. Scherz and J. Stöhr for discussions. We acknowledge support from the FLASH staff. Financial support was given to M.B. by the VolkswagenStiftung. Further support was given by the German Federal Ministry of Education and Research through the priority programme FLASH: “Matter in the light of ultrashort and extremely intense X-ray pulses” and contract number 05K10PK2, and also by the Deutsche Forschungsgemeinschaft through the graduate school: “Physics with new advanced coherent radiation sources”.

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All authors contributed to planning parts of the experiment. Research was conducted by F.S., C.T., N.P., C.S.-L. and M.B. Data analysis and interpretation was done by M.B., S.S. and A.F. The formalism was developed and the manuscript was written by M.B. with input from all co-authors.

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Correspondence to M. Beye.

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The authors declare no competing financial interests.

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Beye, M., Schreck, S., Sorgenfrei, F. et al. Stimulated X-ray emission for materials science. Nature 501, 191–194 (2013).

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