  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.
