Unusual time-delayed changes in the x-ray diffraction parameters of ${\mathrm{LiNbO}}_3$ and ${\mathrm{LiNbO}}_3:\text{Fe}$ crystals were observed under nanosecond laser impact. Subnanosecond time resolution in the registration of diffraction rocking curve (DRC) dynamics was achieved through the synchronization of a 4 ns laser pulse with the circulation phase of electron bunches within a synchrotron storage ring. The response of the crystals to optical impact resulted in a reversible center-of-mass shift and integral intensity decrease of the DRC recovering in $\sim 35$ ns. The dynamics of lattice deformation indicates the process of formation and subsequent decay of an electrical charged layer near the surface due to directed migration of photoelectrons as a result of the bulk photovoltaic effect. The drop in the integral intensity of the DRCs is apparently caused by a running wave generated by a sharp change in the deformation of the crystal lattice. In the case of the nominally undoped crystal, the time-delayed processes occur within the same time interval but with significantly smaller amplitudes.

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• Lattice dynamics
• Photoinduced effect
• Ultrafast phenomena
• X-ray diffraction