Chirality is widespread in nature, playing a fundamental role in biochemical processes and in the origin of life itself. The observation of dynamics in chiral molecules is crucial for the understanding and control of the chiral activity of photoexcited states. One of the most promising techniques for the study of photoexcited chiral systems is time-resolved photoelectron circular dichroism (TR-PECD), which offers an intense and sensitive probe for vibronic and geometric molecular structure as well as electronic structures, and their evolution on a femtosecond timescale. However, the nonlocal character of the PECD effect, which is imprinted during the electron scattering off the molecule, makes the interpretation of TR-PECD experiments challenging. In this respect, core photoionization is known to allow site and chemical sensitivity to photelectron spectroscopy. Here we demonstrate that TR-PECD utilizing core-level photoemission enables probing the chiral electronic structure and its relaxation dynamics with atomic site sensitivity. Following UV pumped excitation to a $3s$ Rydberg state, fenchone enantiomers (${\mathrm{C}}_{10}{\mathrm{H}}_{16}\mathrm{O}$) were probed on a femtosecond scale using circularly polarized soft x-ray light pulses provided by the free-electron laser FERMI. C $1s$ binding energy shifts caused by the redistribution of valence electron density in this $3s$-valence-Rydberg excitation allowed us to measure transient PECD chiral responses with an enhanced C atom site selectivity compared to that achievable in the ground state molecule. This chemical-specific, site-specific, and enantiosensitive observation of the electronic structure of a transiently photoexcited chiral molecule is expected to pave the way toward chiral femtochemistry probed by core-level photoemission.

We present a robust, three-stage optical parametric amplifier driven by a Ti:Sapphire ultrafast laser system that implements passive carrier-envelope phase stabilization and directly generates five-cycle mid-IR pulses by dispersion compensation. The source is based on potassium titanyl arsenate crystals and exploits intra-pulse difference-frequency seed generation in the mid-IR. This source will be particularly suited for applications in strong-field physics, such as high order harmonic generation and photoelectron spectroscopy.

We present a laser-based neutron source that produces 1.8 × 10 5 neutrons/s with a conversion rate of 7.8 × 10 5 neutrons/J . Laser pulses of 12 fs and 23 mJ were focused onto a 430 -nm -thick heavy water liquid sheet at a 10 Hz repetition rate. The resulting peak intensity of 4 × 10 18 W/cm 2 accelerated deuterium ions from the target rear side to a kinetic energy of 1 MeV. This deuteron beam induced H 2 ( d , n ) 3 He fusion reactions in a deuterated polyethylene target, producing fast neutrons. The neutron yield was measured using two independent detection systems: the LILITH time-of-flight spectrometer, consisting of eight plastic scintillators covering nearly 180 ∘ , and a calibrated bubble detector spectrometer. The neutron yield per laser shot is 35 times higher than that recently achieved by lasers with comparable pulse energies, while the conversion rate is the highest ever achieved by continuously operating, sub-100 fs lasers. The generated neutrons are emitted from an area of 0.65 cm 2 corresponding to the deuteron beam spot on the catcher. Their angular distribution is peaked in forward and backward directions in agreement with the literature data on the angular distribution of H 2 ( d , n ) 3 He reaction. The system operated continuously for several hours per day with an unprecedented stability of 5 % .

High-order harmonic generation has become a standard technique for producing attosecond extreme ultraviolet (XUV) pulses in the laboratory, yet the high flux necessary for nonlinear XUV photoionization remains accessible to only a few research groups. Here, we introduce the SYLOS Compact high-harmonic beamline at the Extreme Light Infrastructure Attosecond Light Pulse Source, specifically designed to provide the flux required for nonlinear optics in the XUV. We present a detailed characterization of the beam line demonstrating its capability to generate and utilize both intense attosecond pulse trains and isolated attosecond pulses. We further showcase the 2-XUV–photon double ionization of neon (Ne) and argon (Ar), achieved in a user campaign. The results underscore the beamline’s capability to support cutting-edge attosecond experiments and investigations of ultrafast electron dynamics on the attosecond scale.

Synopsis: We present a high-energy mid-infrared optical parametric amplifier source tunable between 2.8 and 3.8 μm for strong-field applications. We exploited this source in combination with a 800 nm source for generating high-order harmonics in atoms and molecules in a two-color pulse scheme.