Nanoscale heterogeneous dynamics probed by nanosecond x-ray speckle visibility spectroscopy

TL;DR

This study uses ultrafast x-ray speckle visibility spectroscopy at a free electron laser to observe nanosecond-scale heterogeneous dynamics in a colloidal jet, revealing flow heterogeneity at the nanoscale.

Contribution

It introduces a novel methodology for probing nano- and atomic-scale heterogeneous fluctuations in complex matter with x-ray free electron lasers.

Findings

Measured particle flow rate in colloidal jet.

Revealed heterogeneous flow field within the jet.

Established foundation for nanoscale fluctuation studies.

Abstract

We report observations of nanosecond nanometer scale heterogeneous dynamics in a free flowing colloidal jet revealed by ultrafast x-ray speckle visibility spectroscopy. The nanosecond double-bunch mode of the Linac Coherent Light Source free electron laser enabled the production of pairs of femtosecond coherent hard x-ray pulses. By exploring the anisotropic summed speckle visibility which relates to the correlation functions, we are able to evaluate not only the average particle flow rate in a colloidal nanoparticle jet, but also the heterogeneous flow field within. The reported methodology presented here establishes the foundation for the study of nano- and atomic-scale heterogeneous fluctuations in complex matter using x-ray free electron laser sources.