Using Diffuse Scattering to Observe X-Ray-Driven Nonthermal Melting

Abstract

We present results from the SPring-8 Angstrom Compact free electron LAser (SACLA) XFEL facility, using a high intensity ($\sim 10^{20}$W/cm${}^2$) X-ray pump X-ray probe scheme to observe changes in the ionic structure of silicon induced by X-ray heating of the electrons. By avoiding Laue spots in the scattering signal from a single crystalline sample, we observe a rapid rise in diffuse scattering, which we attribute to a loss of lattice order and a transition to a liquid state within 100 fs of irradiation, a timescale which agrees well with first principles simulations, but is faster than that predicted by purely inertial behavior. This method is capable of observing liquid scattering without masking or filtering of signal from the ambient solid, allowing the liquid structure to be measured throughout and beyond the phase change.

6 pages, 5 figures. Updated title and abstract

References in corpus (1)

• Thermal and nonthermal melting of silicon under femtosecond x-ray irradiation

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• Nonthermal effects in solids after swift heavy ion impact
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• FEL stochastic spectroscopy revealing silicon bond softening dynamics