Diffraction-Detected Sum Frequency Generation: Novel Ultrafast X‑ray Probe of Molecular Dynamics

We propose a novel time-resolved diffraction technique based on sum frequency generation that combines an optical pump with an X-ray stimulated Raman probe. Simulations are presented for formyl fluoride, which is nonchiral in the ground state and evolves into a chiral nonplanar structure in the first excited state upon excitation by a circularly polarized UV pump. A coherently controlled elliptically polarized pump is used to prepare the molecule in a selected enantiomer and the chiral interconversion dynamics is then monitored by the probe diffraction

Coupled Electronic and Nuclear Motions during Azobenzene Photoisomerization Monitored by Ultrafast Electron Diffraction

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Phase Cycling RT-TDDFT Simulation Protocol for Nonlinear XUV and X‑ray Molecular Spectroscopy

Real-time time-dependent density functional theory (RT-TDDFT) provides a practical algorithm for propagating a many-electron system driven by external laser fields. The fields are included nonperturbatively in the propagation, and the molecular reduced single-electron density operator and various spectroscopic and diffraction signals can be computed directly, avoiding the expensive calculation of many-body states. Nonlinear optical signals contain contributions of multiple pathways. A phase cycling protocol is implemented in order to separate these pathways. Simulations of XUV four-wave mixing signals in the CO molecule are compared with ab initio sum-over-states calculations

Hard X-ray transient grating spectroscopy on bismuth germanate

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