Time-Resolved Photoelectron Spectroscopy at 100 kHz: Commissioning of a COLTRIMS setup equipped with a table-top high-repetition XUV source 

It is a long-term goal pursued by the ultrafast science community to track the dynamics of photoexcited molecules on an ultrashort time scale. The seminal work by Albert Stollow et al. ^[1] showed that time-resolved photoelectron spectroscopy (TRPES) is a unique tool to characterize the full electronic dynamics by tracking the valence electrons on a femtosecond time scale. Over the past years, table-top photon sources that can generate light in the extreme ultraviolet (XUV) regime through High harmonic generation (HHG) have proven to be an efficient way to carry out such studies. Utilizing XUV photons as a probe has the advantage of excitation or ionization via single-photon absorption for the entire reaction pathway, including the ground state of the photoproducts. The combination of XUV sources driven by high-repetition ultrashort lasers and high-resolution COLTRIMS (Cold Target Recoil Ion Momentum Spectroscopy) setup paves the way to follow the electronic dynamics in a coincidence detection scheme. We are currently commissioning such a setup for pump-probe experiments using a 100-kHz White Dwarf femtosecond laser from Class 5 Photonic with dual OPCPA outputs. The high-repetition-rate, high- energy, 27-fs output of OPCPA 1 drives the XUV source, while the tunable output of OPCPA 2 acts as a pump pulse that can cover the range from the deep UV to the NIR. By capturing coincidence events of all photo products, both ions and electrons, with the COLTRIMS, we aim to perform TRPES of molecular gas targets in coincidence with momentum-resolved photoions.

[1] Femtosecond Time-Resolved Photoelectron Spectroscopy, Chem. Rev. 2004, 104, 4, 1719–1758.