Controlling X-rays with light


Ultrafast X-ray science is an exciting frontier that promises the visualization of electronic, atomic and molecular dynamics on atomic time and length scales. A largely unexplored area of ultrafast X-ray science is the use of light to control how X-rays interact with matter. To extend control concepts established for long-wavelength probes to the X-ray regime, the optical control field must drive a coherent electronic response on a timescale comparable to femtosecond core-hole lifetimes. An intense field is required to achieve this rapid response. Here, an intense optical control pulse is observed to efficiently modulate photoelectric absorption for X-rays and to create an ultrafast transparency window. We demonstrate an application of X-ray transparency relevant to ultrafast X-ray sources: an all-photonic temporal cross-correlation measurement of a femtosecond X-ray pulse. The ability to control X-ray–matter interactions with light will create new opportunities for present and next-generation X-ray light sources.

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Figure 1: Relevant atomic states contributing to X-ray absorption.
Figure 2: X-ray absorption spectrum for Ne in the absence of a coupling laser.
Figure 3: The fractional change in X-ray transmission induced by the coupling laser in the parallel polarization configuration (ɛLɛX).
Figure 4: Polarization dependence of the fractional change in X-ray transmission and the calculated X-ray absorption cross-section for laser-dressed neon.
Figure 5: Cross-correlation measurement of the femtosecond X-ray pulse duration from the ALS slicing source.
Figure 6: Layout of the femtosecond spectroscopy beamline at the ALS.


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We thank C. Buth and S.E. Harris for enlightening discussions and D.L. Ederer, T. Weber, R.W. Schoenlein and P. Heimann for experimental support during early stages of this project. This work was supported by the Chemical Sciences, Geosciences, and Biosciences Division of the Office of Basic Energy Sciences, Office of Science, US Department of Energy, under Contract No. DE-AC02-06CH11357 and DE-AC02-05CH11231. This work was carried out at the Advanced Light Source, Lawrence Berkeley National Laboratory, and was supported by the Office of Science, Office of Basic Energy Sciences, of the US Department of Energy under Contract No. DE-AC02-05CH11231.

Author information

T.E.G., M.P.H., A.B., S.H.S. and L.Y. contributed to the design of the experiment. T.E.G., M.P.H. and B.R. were responsible for the femtosecond X-ray beamline and control laser performance. T.E.G., M.P.H., S.H.S., T.K.A., J.V.T., E.P.K., B.K. and L.Y. collected the data. H.R.V. and R.S. carried out the supporting theoretical calculations. Data analysis and interpretation were done by S.H.S., T.E.G., M.P.H., E.P.K., R.S. and L.Y.

Correspondence to L. Young.

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Glover, T., Hertlein, M., Southworth, S. et al. Controlling X-rays with light. Nature Phys 6, 69–74 (2010) doi:10.1038/nphys1430

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