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Time-resolved transient grating (TG) spectroscopy facilitates detailed studies of electron dynamics and transport phenomena by means of a periodic excitation of matter with coherent ultrashort light pulses. Several current and next generation free-electron laser (FEL) facilities provide fully coherent pulses with few femtosecond pulse durations and extreme ultraviolet (XUV) photon energies. Thus, they allow for transient grating experiments with periodicities as small as tens of nanometers and with element specific photon energies. Here, we demonstrate the element specificity of XUV TG (X-TG) experiments by tuning the photon energy across the Si L₂,₃-edge of Si₃N₄. We observe a shortening of the signal decay when increasing the XUV photon energy above the absorption edge. The analysis of the wavelength dependent signal shows that the faster decay is driven by the increase in the charge carrier density. From the decay constants the interband Auger coefficient at elevated temperatures and high electron densities has been determined., Swiss National Science Foundation (SNF) (Grant 200021_165550/1)

The Messinian Salinity Crisis (MSC), which widely affected the whole Mediterranean basin, induced rapid and spectacular palaeoenvironmental changes. It led to a major erosion of the onshore areas and the upper parts of the continental shelves and slopes, as well as important evaporitic deposits in the offshore deep basins. The Corsica Basin belongs to the so-called “intermediate-depth basin” type because of its location between the coastal plain–shelf area of East Corsica and deeper marine basins in the northern Tyrrhenian Sea. The MSC event took place in the Corsica Basin during a period of active regional tectonics, contemporaneous with the opening of the Tyrrhenian Sea, as well as during the development of the Corsica Basin and the Elba-Pianosa Ridge. Based on the interpretation of high-resolution seismic reflection profiles and a new 1:250,000 scale synthetic geological map, we establish that the MSC is recorded in the Corsica Basin through the occurrence of two sedimentary formations bounded by three remarkable surfaces. These seismic markers suggest local and temporal variations in relative water level and associated depositional environments that differ between the north and south of the Corsica Basin. During the MSC, the northern sector (Golo Basin) was emerged, whereas the southern sector (Orbo Basin) was often flooded or submerged. In the Orbo Basin, the deposits record both an episode of intra-MSC climate change and regional tectonic events. During the MSC, the Corsica Basin was a perched lake, isolated from the deeper Tyrrhenian basins. The connection with the Tyrrhenian basins was re-established during the final stages of the MSC, before the catastrophic Pliocene reflooding, initiated by retrogressive erosion during a relative lowstand. An extensive network of incised valleys was thus established in the Orbo basin, allowing the drainage of the Corsica Basin southwards into the deeper Tyrrhenian basins. These markers record the active regional tectonic c

Femtosecond fluorescence up-conversion, UV-Vis and IR transient absorption spectroscopy are used to study the photo-isomerization dynamics of a new type of zwitterionic photoswitch based on a N-alkylated indanylidene pyrroline Schiff base framework (ZW-NAIP). The system is biomimetic, as it mimics the photophysics of retinal, in coupling excited state charge translocation and isomerization. While the fluorescence lifetime is 140 fs, excited state absorption persists over 230 fs in the form of a vibrational wavepacket according to twisting of the isomerizing double bond. After a short "dark'' time window in the UV-visible spectra, which we associate with the passage through a conical intersection (CI), the wavepacket appears on the ground state potential energy surface, as evidenced by the transient mid-IR data. This allows for a precise timing of the photoreaction all the way from the initial Franck-Condon region, through the CI and into both ground state isomers, until incoherent vibrational relaxation dominates the dynamics. The photo-reaction dynamics remarkably follow those observed for retinal in rhodopsin, with the additional benefit that in ZW-NAIP the conformational change reverses the zwitterion dipole moment direction. Last, the pronounced low-frequency coherences make these molecules ideal systems for investigating wavepacket dynamics in the vicinity of a CI and for coherent control experiments.

Lithologic and stratigraphic evidence from D.S.D.P. Site 398 (3910 m water depth, 1740 m total penetration) and regional seismic reflexion data are placed in the context of the early tectonic evolution of the North Atlantic ocean. The morphology of the western Iberian continental margin is the result of two main tensional episodes dated Permo-Lias and Upper Jurassic - Lower Cretaceous, during which the initial basins between Grand Banks and Iberia were created by subsidence and tilting of continental blocks. A limited oceanic opening had probably occurred in Jurassic time between these two tensional episodes. There was no relative motion during Lower Cretaceous between North America and Iberia. [NOT CONTROLLED OCR]