Roadmap on dynamics of molecules and clusters in the gas phase

This roadmap article highlights recent advances, challenges and future prospects in studies of the dynamics of molecules and clusters in the gas phase. It comprises nineteen contributions by scientists with leading expertise in complementary experimental and theoretical techniques to probe the dynamics on timescales spanning twenty order of magnitudes, from attoseconds to minutes and beyond, and for systems ranging in complexity from the smallest (diatomic) molecules to clusters and nanoparticles. Combining some of these techniques opens up new avenues to unravel hitherto unexplored reaction pathways and mechanisms, and to establish their significance in, e.g. radiotherapy and radiation damage on the nanoscale, astrophysics, astrochemistry and atmospheric science

Transient absorption spectroscopy using high harmonic generation: a review of ultrafast X-ray dynamics in molecules and solids.

Attosecond science opened the door to observing nuclear and electronic dynamics in real time and has begun to expand beyond its traditional grounds. Among several spectroscopic techniques, X-ray transient absorption spectroscopy has become key in understanding matter on ultrafast time scales. In this review, we illustrate the capabilities of this unique tool through a number of iconic experiments. We outline how coherent broadband X-ray radiation, emitted in high-harmonic generation, can be used to follow dynamics in increasingly complex systems. Experiments performed in both molecules and solids are discussed at length, on time scales ranging from attoseconds to picoseconds, and in perturbative or strong-field excitation regimes. This article is part of the theme issue 'Measurement of ultrafast electronic and structural dynamics with X-rays'

Vibronic Dynamics of Photodissociating ICN from Simulations of Ultrafast X‐Ray Absorption Spectroscopy

Ultrafast UV-pump/soft-X-ray-probe spectroscopy is a subject of great interest since it can provide detailed information about dynamical photochemical processes with ultrafast resolution and atomic specificity. Here, we focus on the photodissociation of ICN in the 1Π1 excited state, with emphasis on the transient response in the soft-X-ray spectral region as described by the ab initio spectral lineshape averaged over the nuclear wavepacket probability density. We find that the carbon K-edge spectral region reveals a rich transient response that provides direct insights into the dynamics of frontier orbitals during the I−CN bond cleavage process. The simulated UV-pump/soft-X-ray-probe spectra exhibit detailed dynamical information, including a time-domain signature for coherent vibration associated with the photogenerated CN fragment. © 2020 The Authors. Published by Wiley-VCH Gmb

Electron dynamics in transition metal dichalcogenides utilizing attosecond transient absorption spectroscopy

Strong enhancement of exciton binding has been observed in valence-excitons in the optical regime of 2D materials. We report direct observation of long-lived core-exciton states in transition metal dichalcogenides by attosecond transient absorption spectroscopy in the XUV

Enhanced high-order harmonic generation driven by a wavefront corrected high-energy laser

We developed and implemented an experimental setup for the generation of high-energy high-order harmonics in argon gas for nonlinear experiments in the extreme ultraviolet (XUV) spectral range. High-order harmonics were generated by loosely focusing a high-energy laser pulse centered around 800 nm into a gas cell filled with argon in a phase-matching condition. The wavefront distortions of the driving pulse were corrected by a deformable mirror, and the XUV conversion efficiency was significantly improved due to the excellent beam profile at focus. A high-damage-threshold beam splitter was used to eliminate high-energy driving pulses co-propagating with high-order harmonics. The setup has a potential to provide intense ultrashort XUV pulses reaching the intensity levels required for nonlinear experiments in the XUV spectral range