## 2 Experiment  
The pump-probe experiments were performed at the Linac Coherent Light Source (LCLS) [9] in Stanford, USA at the X-ray Pump Probe (XPP) beamline [19]. LCLS was operated in the Self Amplified Spontaneous Emission (SAE) mode [20]. A sketch of the experiment is shown in Figure 1. A double-crystal diamond (111) monochromator with the thicknesses of the monochromator crystals of 100 \(\upmu\)m and 300 \(\upmu\)m, enabled splitting of the primary X-ray beam into a pink (transmitted) and a monochromatic (reflected) branches and simultaneous operation of two beamlines (see Figure 1) [21]. We employed the monochromatic regime of LCLS with the energy of a single XFEL pulse of 8 keV (1.5498 A), energy bandwidth of 4.3 \(\times\) 10\({}^{-5}\)[22], and a pulse duration of about 50 fs as provided by electron bunch measurements at a repetition rate of 120 Hz. The X-ray beam was focused using the compound refractive lenses (CRLs) on the sample down to 50 \(\upmu\)m full width at half maximum (FWHM). The photon flux of the beam at the sample position was about 10\({}^{9}\) ph/pulse. This allowed us to perform measurements in a non-destructive regime. In the experiment, the colloidal crystal was oriented vertically, with its surface perpendicular to the incoming XFEL pulse in the transmission diffraction geometry. Colloidal crystal films were prepared using the vertical deposition method [23] from spherical colloids consisting of two different materials, either polystyrene (PS) or silica. The crystalline films consisted of 30-40 particle layers, depending on the position on the film along the growth direction (the number of crystal layers increases at later growth times). After crystal growth, some of the films were covered with a 20-50 nm thick aluminum layer to increase interaction with the IR laser. In total, three types of samples were investigated: PS colloidal crystals, PS colloidal crystals covered by Al, and silica crystals, with different sphere diameters of 420 \(\pm\) 9 nm, 376 \(\pm\) 8 nm and 238 \(\pm\) 7 nm, respectively. Due to the growing method, the dried colloidal crystal films used in our experiment contain cracksbetween single-crystal regions of about 50 \(\upmu\)m in size. Microscopic images of these samples are shown in Figure 2.  
Series of X-ray diffraction images were recorded using the Cornell-SLAC Pixel Array Detector (CSPAD) megapixel X-ray detector [24], positioned 10 m downstream from the sample, that is comprised of 32 silicon sensors with the pixel size of 110 \(\times\) 110 \(\upmu\)m\({}^{2}\) covering an area approximately 17 \(\times\) 17 cm\({}^{2}\). This experimental arrangement provided resolution of 0.5 \(\upmu\)m\({}^{-1}\) per pixel in reciprocal space. The 2.3 megapixels of the detector were read out at 120 Hz, encoded at 14 bits per pixel. In order to prevent damage of the detector, a 5 \(\times\) 5 mm\({}^{2}\) Al beamstop was placed in front of it. To reduce air scattering, a 10 m long flight tube filled with He was mounted between the sample and the detector. A Ti:sapphire IR laser was used to excite the colloidal crystal film. The pump pulses were generated with a wavelength \(\lambda\) = 800 nm (1.5497 eV) and duration about 50 fs (FWHM). The size of the laser footprint on the sample was 100 \(\upmu\)m (FWHM) and, thus, twice larger in comparison to the X-ray beam. The corresponding intensity of the laser pulses was on the order of 10\({}^{13}\) W/cm\({}^{2}\)\" The IR laser pulses were propagating along the XFEL pulses and were synchronized to the pulses from the XFEL with less than 0.5 ps jitter. The IR laser energy was controlled by rotation of the optical axis of a waveplate (see Figure 1), and was calibrated by power sensor at the position of the sample. The measured calibration curve is presented in Figure 3. Zero degrees of waveplate angle corresponds to the minimum and 10 degrees correspond to the maximum calibrated energy and intensity of the IR laser.