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Atomic inner-shell X-ray laser at 1.46 nanometres pumped by an X-ray free-electron laser



Since the invention of the laser more than 50 years ago, scientists have striven to achieve amplification on atomic transitions of increasingly shorter wavelength1,2,3,4,5,6,7. The introduction of X-ray free-electron lasers8,9,10 makes it possible to pump new atomic X-ray lasers11,12,13 with ultrashort pulse duration, extreme spectral brightness and full temporal coherence. Here we describe the implementation of an X-ray laser in the kiloelectronvolt energy regime, based on atomic population inversion and driven by rapid K-shell photo-ionization using pulses from an X-ray free-electron laser. We established a population inversion of the Kα transition in singly ionized neon14 at 1.46 nanometres (corresponding to a photon energy of 849 electronvolts) in an elongated plasma column created by irradiation of a gas medium. We observed strong amplified spontaneous emission from the end of the excited plasma. This resulted in femtosecond-duration, high-intensity X-ray pulses of much shorter wavelength and greater brilliance than achieved with previous atomic X-ray lasers. Moreover, this scheme provides greatly increased wavelength stability, monochromaticity and improved temporal coherence by comparison with present-day X-ray free-electron lasers. The atomic X-ray lasers realized here may be useful for high-resolution spectroscopy and nonlinear X-ray studies.

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Figure 1: Experimental scheme.
Figure 2: Single-shot spectra of the atomic XRL line and transmitted XFEL pump.
Figure 3: Dependence of the XRL output on pump power.
Figure 4: Simulation of the gain.


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This work was performed under the auspices of the US Department of Energy by Lawrence Livermore National Laboratory (LLNL; DE-AC52-07NA27344) and was supported by LLNL’s LDRD programme, 09-LW-044. Portions of this research were carried out at the Linac Coherent Light Source, a national user facility operated by Stanford University on behalf of the US Department of Energy, Office of Basic Energy Sciences. J.J.R., M.P. and D.R. were supported by the US Department of Energy Basic Energy Sciences AMOS Program. We thank M. J. Pivovaroff and K. A. van Bibber for their encouragement and support for this project; R. W. Lee, T. Ditmire, L. Young, R. Falcone and S. Le Pape for discussions of the experimental design; J.-C. Castagna, C.-M. Tsai, S. Schorb, M. L. Swiggers and M. Messerschmidt for their assistance with the experiment; M. J. Bogan for the loan of the X-ray CCD camera and A. Barty for the design of Fig. 1. We also acknowledge support of the LCLS software engineers for the control and data acquisition. We are indebted to the LCLS operating team for their support during beam time in achieving the necessary pulse energies for this experiment.

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Authors and Affiliations



N.R. and R.A.L. had the idea for the experiment, which was designed with J.J.R., J.D. and J.D.B. N.R. developed theory and models of the data. J.D.B. and C.B. were responsible for the AMO beamline at LCLS. R.H. designed the neon gas cell. D.R. and M.P. calibrated and installed the X-ray spectrograph. D.R., M.P., J.D.B., C.B., J.D., F.A., N.R., J.J.R. and R.A.L. carried out the experiment. S.P.H.-R. and R.A.L. performed hole-drilling tests on the gas-cell window materials. A.G. helped in the set-up of the experiment. J.D., R.A.L. and N.R. designed the filters. N.R., D.R. and R.A.L. analysed and interpreted the data. R.A.L. estimated the gain and gain–length product. N.R. wrote the paper with contributions from R.A.L., J.D., D.R. and J.J.R.

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Correspondence to Nina Rohringer.

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The authors declare no competing financial interests.

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Rohringer, N., Ryan, D., London, R. et al. Atomic inner-shell X-ray laser at 1.46 nanometres pumped by an X-ray free-electron laser. Nature 481, 488–491 (2012).

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