Progress and prospects in nonlinear extreme-ultraviolet and X-ray optics and spectroscopy

Generalization of One-Center Nonorthogonal Configuration Interaction Singles to Open-Shell Singlet Reference States: Theory and Application to Valence-Core Pump-Probe States in Acetylacetone

“…Time-resolved near-edge X-ray absorption (TR-NEXAS) experiments aim to track the ensuing dynamics of molecular systems after a perturbation with light by monitoring the NEXAS (equivalently termed NEXAFS, XANES, or often simply XAS) features of the species involved as a function of time. With advances in synchrotron slicing techniques and the advent of free-electron lasers, the time resolution of modern TR-NEXAS experiments is well into the femtosecond regime. , Furthermore, improvements in high-harmonic generation have brought extreme UV and soft X-ray femtosecond pulses in the water window (270–550 eV) to table-top laser equipment. , With element and site specificity, as well as strong sensitivity to the electronic environment of the species being probed, the TR-NEXAS experiments enabled by these new technologies have already provided fundamental insight into the role of dark singlet and triplet states in the electronic relaxation of organic molecules and directly tracked the nuclear motion of small molecules post strong-field ionization. − …”

Time-Dependent Resonant Inelastic X-ray Scattering of Pyrazine at the Nitrogen K-Edge: A Quantum Dynamics Approach

“…The development of high-brilliance synchroton X-ray radiation sources − and X-ray free electron lasers − has enabled techniques that require high photon flux such as resonant inelastic X-ray scattering (RIXS) and its extension into the ultrafast time domain. − RIXS constitutes a Raman scattering process in which the system is resonantly excited into short-lived core-hole states and spontaneously decays back to the electronic ground and excited states. , This technique combines the element specificity of core-level spectroscopy with the ability to reach valence-excited states across a wide spectral range (>20 eV) even in the condensed phase and at a spectral resolution that is not limited by the core-hole lifetime broadening, making it a versatile and promising tool to study the local electronic structure in complex molecular systems. RIXS to ground and valence-excited states has already been applied in various areas such as the nature of hydrogen-bond interactions, − the photochemistry of transition-metal complexes, − ultrafast dynamics of molecules on surfaces, , proton transfer dynamics, ,, or core-excited state dynamics. − …”

Generation of interferometrically stable pulse pairs from a free-electron laser using a birefringent interferometer

“…The development of high brilliance XUV and x-ray FELs with femto-to attosecond pulse durations opens up many possibilities for nonlinear spectroscopy [1] and coherent control experiments [2]. Many of the proposed experimental schemes [3][4][5] require the generation of sequences of multiple XUV/xray pulses with precisely controlled timing.…”