%0 Journal Article
%A Kroll, Thomas
%A Weninger, Clemens
%A Alonso-Mori, Roberto
%A Sokaras, Dimosthenis
%A Zhu, Diling
%A Mercadier, Laurent
%A Majety, Vinay P.
%A Marinelli, Agostino
%A Lutman, Alberto
%A Guetg, Marc W.
%A Decker, Franz-Josef
%A Boutet, Sébastien
%A Aquila, Andy
%A Koglin, Jason
%A Koralek, Jake
%A DePonte, Daniel P.
%A Kern, Jan
%A Fuller, Franklin D.
%A Pastor, Ernest
%A Fransson, Thomas
%A Zhang, Yu
%A Yano, Junko
%A Yachandra, Vittal K.
%A Rohringer, Nina
%A Bergmann, Uwe
%T Stimulated X-Ray Emission Spectroscopy in Transition Metal Complexes
%J Physical review letters
%V 120
%N 13
%@ 1079-7114
%C College Park, Md.
%I APS
%M PUBDB-2019-00874
%P 133203
%D 2018
%X 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 ∼10<sup>20</sup>  W/cm<sup>2</sup> 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. 
%F PUB:(DE-HGF)16
%9 Journal Article
%$ pmid:29694162
%U <Go to ISI:>//WOS:000428394800008
%R 10.1103/PhysRevLett.120.133203
%U https://bib-pubdb1.desy.de/record/419010