Time-resolved photoelectron spectroscopy using synchrotron radiation time structure

TLDR

Synchrotron radiation time structure is increasingly used to study dynamic material properties, but its wide accessible time domain limits pump‑probe experiments. To enable photoelectron spectroscopy from milliseconds to picoseconds, the authors require measuring the creation time of each photoelectron. They replaced the standard CCD camera with a 5‑ns‑resolution delay‑line detector on a Scienta SES 2002 analyzer, matching the SOLEIL synchrotron time structure. Characterization of electron time‑of‑flight versus kinetic energy and pass energy shows a time spread below 140 ns even at 10 eV, confirming that pump‑probe photoelectron spectroscopy can achieve the SOLEIL pulse‑width resolution and beamline performance.

Abstract

Synchrotron radiation time structure is becoming a common tool for studying dynamic properties of materials. The main limitation is often the wide time domain the user would like to access with pump-probe experiments. In order to perform photoelectron spectroscopy experiments over time scales from milliseconds to picoseconds it is mandatory to measure the time at which each measured photoelectron was created. For this reason the usual CCD camera-based two-dimensional detection of electron energy analyzers has been replaced by a new delay-line detector adapted to the time structure of the SOLEIL synchrotron radiation source. The new two-dimensional delay-line detector has a time resolution of 5 ns and was installed on a Scienta SES 2002 electron energy analyzer. The first application has been to characterize the time of flight of the photoemitted electrons as a function of their kinetic energy and the selected pass energy. By repeating the experiment as a function of the available pass energy and of the kinetic energy, a complete characterization of the analyzer behaviour in the time domain has been obtained. Even for kinetic energies as low as 10 eV at 2 eV pass energy, the time spread of the detected electrons is lower than 140 ns. These results and the time structure of the SOLEIL filling modes assure the possibility of performing pump-probe photoelectron spectroscopy experiments with the time resolution given by the SOLEIL pulse width, the best performance of the beamline and of the experimental station.