  We present a new set up for resonant inelastic hard X-ray scattering at the
Bernina beamline of SwissFEL with energy, momentum, and temporal resolution.
The compact R=0.5 m Johann-type spectrometer can be equipped with up to 3
crystal analysers and allows efficient collection of RIXS spectra. Optical
pumping for time-resolved studies can be realized with a broad span of optical
wavelengths. We demonstrate the performance of the set-up at overall ~180 meV
resolution in a study of ground-state and photoexcited (at 400 nm) honeycomb 5d
iridate $\alpha$-$\mathrm{Li_2IrO_3}$. Steady-state RIXS spectra at the Iridium
${L_3}$-edge (11.214 keV) have been collected and are in very good agreement
with data collected at synchrotrons. The time-resolved RIXS transients (pumped
minus unpumped spectra) exhibit changes in the energy-loss region <2 eV, whose
features mostly result from the hopping nature of 5d electrons in the honeycomb
lattice. These changes are ascribed to modulations of the Ir-to-Ir intersite
transition scattering efficiency, which we associate to a transient screening
of the on-site Coulomb interaction.

Strongly Correlated Electrons