Self-referenced coherent diffraction x-ray movie of Angstrom- and femtosecond-scale atomic motion

TL;DR

This paper demonstrates a novel x-ray diffraction technique that captures real-time atomic motion within molecules at Angstrom and femtosecond scales, revealing detailed internal dynamics with high sensitivity.

Contribution

The study introduces a new heterodyne x-ray diffraction method that uses the initial static charge distribution as a reference to image molecular internal motion in unprecedented detail.

Findings

Visualized coherent vibrational motion and dispersion.

Observed molecular dissociation and rotational dephasing.

Demonstrated high spatial and temporal resolution imaging.

Abstract

Time-resolved femtosecond x-ray diffraction patterns from laser-excited molecular iodine are used to create a movie of intramolecular motion with time and space resolution of $30~$fs and $0.3$ \AA . The high spatial fidelity is due to interference between the moving excitation and the static initial charge distribution. This x-ray interference has not been employed to image internal motion in molecules before. The initial state is used as the local oscillator for heterodyne amplification of the excited charge distribution to retrieve real-space movies of atomic motion on \AA ngstrom and femtosecond scales. Coherent vibrational motion and dispersion, dissociation, and rotational dephasing are all clearly visible in the data, thereby demonstrating the stunning sensitivity of heterodyne methods.