Dynamics of colloidal crystals studied by pump-probe experiments at FLASH

TL;DR

This study uses pump-probe experiments at FLASH to observe ultrafast structural dynamics in colloidal crystals, revealing GHz frequency vibrations and correlating them with theoretical models of sphere vibrations.

Contribution

It demonstrates a novel time-resolved IR and XUV diffraction technique to analyze picosecond-scale dynamics in colloidal crystals at an advanced facility.

Findings

Periodic modulations at 4-5 GHz detected in colloidal crystals.

Theoretical eigenfrequency of 5.07 GHz matches observed vibrations.

Ultrafast structural dynamics characterized with picosecond resolution.

Abstract

We present a time-resolved infrared (IR) pump and extreme-ultraviolet (XUV) probe diffraction experiment to investigate ultrafast structural dynamics in colloidal crystals with picosecond resolution. The experiment was performed at the FLASH facility at DESY with a fundamental wavelength of 8 nm. In our experiment, the temporal changes of Bragg peaks were analyzed and their frequency components were calculated using Fourier analysis. Periodic modulations in the colloidal crystal were localized at a frequency of about 4-5 GHz. Based on the Lamb theory, theoretical calculations of vibrations of the isotropic elastic polystyrene spheres of 400 nm in size reveal a 5.07 GHz eigenfrequency of the ground (breathing) mode.