Split-pulse X-ray photon correlation spectroscopy with seeded X-rays from X-ray laser to study atomic-level dynamics

Abstract

With their brilliance and temporal structure, X-ray free-electron laser can unveil atomic-scale details of ultrafast phenomena. Recent progress in split-and-delay optics (SDO), which produces two X-ray pulses with time-delays, offers bright prospects for observing dynamics at the atomic-scale. However, their insufficient pulse energy has limited its application either to phenomena with longer correlation length or to measurement with a fixed delay-time. Here we show that the combination of the SDO and self-seeding of X-rays increases the pulse energy and makes it possible to observe the atomic-scale dynamics in a timescale of picoseconds. We show that the speckle contrast in scattering from water depends on the delay-time as expected. Our results demonstrate the capability of measurement using the SDO with seeded X-rays for resolving the dynamics in temporal and spatial scales that are not accessible by other techniques, opening opportunities for studying the atomic-level dynamics.

From Femtoseconds to Hours—Measuring Dynamics over 18 Orders of Magnitude with Coherent X-rays

“…(a) By changing the pulse width, the speckle contrast obtained by XSVS follows expectations from molecular dynamics simulations[30]. (b) Longer times are achieved using a split-and-delay device at SACLA, where the speckle contrast depends on the pulse intensity suggesting radiation-induced dynamics[31]. Figures are reprinted from[30,31] under CC-BY 4.0.…”

“…[30]. (b) Longer times are achieved using a split-and-delay device at SACLA, where the speckle contrast depends on the pulse intensity suggesting radiation-induced dynamics [31]. Figures are reprinted from [30,31] under CC-BY 4.0.…”

“…The inset shows the closed box that is flushed with helium to reduce parasitic scattering. Shinohara et al applied the split-and-delay line of SACLA for studying the dynamics of liquid water [31]. By using self-seeded X-ray pulses, the spectral width was reduced and thus the pulse energy that passed the split-and-delay-line increased.…”

“…The main part of this review discusses dynamics studies from the last 10 years, focussing on the new possibilities thanks to accessing faster timescales at storage rings and the performance of XPCS at FEL sources. Recent highlights that will be addressed in this review include the observation of two types of liquid water [29] as well as probing realtime dynamics in liquid water on femto-to picosecond time scales [30,31]. Furthermore, new routes of understanding stress relaxation in glasses have been revealed recently [32].…”

Analysis Strategies for MHz XPCS at the European XFEL

“…with the speckle contrast β that is determined by the coherence properties of the beamline [5]. While XPCS at storage-ring sources typically covers dynamics in the range between hours down to (sub-)millisecond time scales, its main application at XFEL facilities are fast time scales in the femto-to nanosecond domain [6][7][8], using either double-pulse approaches via split-and-delay devices or modification of the X-ray pulse length between a few to about 100 fs. The apparent gap of time scales between nano-and milliseconds originates from the limitations of the time resolution of two-dimensional detectors.…”