Experimental Demonstration of Attosecond Pump-Probe Spectroscopy with an X-ray Free-Electron Laser

TL;DR

This paper demonstrates the generation and control of sub-femtosecond pulse pairs from an X-ray free-electron laser, enabling high-resolution pump-probe experiments to study electronic dynamics with atomic site specificity.

Contribution

It presents a novel method to produce and precisely control sub-femtosecond X-ray pulses for pump-probe spectroscopy.

Findings

Pulse delay control down to 270 attoseconds

Successful pump-probe measurement on para-aminophenol

Demonstration of sub-femtosecond resolution in X-ray spectroscopy

Abstract

Pump-probe experiments with sub-femtosecond resolution are the key to understanding electronic dynamics in quantum systems. Here we demonstrate the generation and control of sub-femtosecond pulse pairs from a two-colour X-ray free-electron laser (XFEL). By measuring the delay between the two pulses with an angular streaking diagnostic, we characterise the group velocity of the XFEL and demonstrate control of the pulse delay down to 270 as. We demonstrate the application of this technique to a pump-probe measurement in core-excited para-aminophenol. These results demonstrate the ability to perform pump-probe experiments with sub-femtosecond resolution and atomic site specificity.