Extreme Light Infrastructure Beamlines

Superfluid He nanodroplets resonantly excited by extreme ultraviolet (XUV) pulses can relax via interatomic coulombic decay (ICD), generally considered an ultrafast process. Here, we introduce a novel approach to probe the dynamics of ICD in He nanodroplets over timescales ranging from femtoseconds to nanoseconds. Our method relies on detecting XUV fluorescence emitted from the nanodroplets as they are driven into a nanoplasma by subsequent intense infrared pulses. Nanoplasma ignition is facilitated by tunnel ionization of XUV-excited He^* atoms attached to the droplets; it thus serves as a sensitive probe of their relaxation dynamics. The observed nanosecond-scale decay is attributed to ICD between pairs of He^* atoms undergoing roaming motion on the droplet surface, as supported by quantum-mechanical and classical model calculations.

Abstract The interaction of a laser with an over-critical foam of high-density contrast is investigated numerically using the hydrodynamic code FLASH to better understand the effect of the foam structure on the propagation of shocks. Two representative cases are compared to the case of a homogeneous material with a density equal to the foam average density. In the first case, the whole foam structure is directly exposed to the laser. We found that a shock wave is generated and has similar properties to those of the homogeneous case. In the second case, the laser penetration into the foam is blocked by an overcritical plasma layer that acts as a laser-driven piston. Thus, the laser-driven shock wave homogenizes the solid structural elements in the foam. The propagation speed and internal structure of the transient zone are different, and a significant amount of energy is stored in turbulent kinetic energy. The properties of turbulence are also discussed.

We demonstrate a very strong laser gain in the near UV, at 391 nm, involving one- and two-photon transitions between initial and final levels of the transition. This opens the way to the realization of all-optical lasers at short wavelengths. The amplifying medium is N2+ at low density, pumped by an intense laser source at a longer wavelength, i.e., 800 nm. It is probed by measuring with femtosecond precision the absorption of XUV high harmonics through the gas, displaying the evolution of the relevant electronic levels during the amplification process. We show the role of a third level forming a "V scheme" with the initial and final levels.

Gallium sulphide (GaS) is an emerging monochalcogenide material that has recently attracted interest in optical technologies due to its tunable bandgap in the near-UV region. In this work, we employ in situ , in-operando X-ray diffraction to investigate local atomic modifications in GaS induced by 400-nm femtosecond laser pulses. We identify the energy threshold at which irreversible structural changes occur and observe a laser-induced elongation of the unit cell along the c -axis. This elongation is expected to enhance the anisotropy of the material’s physical properties. Ab initio calculations further reveal that the experimentally observed ≈ 10% elongation along the c -axis leads to a transition from a direct to an indirect bandgap, accompanied by a bandgap increase of approximately 0.45 eV. Additional ab-initio optical simulations show that this structural transformation results in a nearly constant in-plane refractive index contrast of Δ n ≈ 0.1 across a wide spectral range, from the visible to the near-infrared, with negligible optical losses, which could be of interest for reconfigurable photonics applications.

A new Escherichia coli laboratory evolution screen for detecting plant ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) mutations with enhanced CO2-fixation capacity has identified substitutions that can enhance plant productivity. Selected were a large subunit catalytic (Met-116-Leu) mutation that increases the kcatc of varying plant Rubiscos by 25% to 40% and a solubility (Ala-242-Val) mutation that improves plant Rubisco biogenesis in E. coli 2- to 10-fold. Plastome transformation of either mutation into the tobacco plastome rbcL gene had no impact on leaf Rubisco production, photosynthesis or plant growth. However, tobacco transformed with low-abundance hybrid Arabidopsis Rubisco coding M116L improved plant exponential growth rate by ~75% relative to unmutated hybrid enzyme, with the A242V substitution increasing both hybrid Rubisco production and plant growth by ~50%. Our identification of mutations with the potential to enhance plant growth bodes well for broadening the survey of Rubisco sequence space for catalytic switches that can impart more substantive plant productivity improvements.

In this paper we present the results from the study on the self-induced (ghost) signal observed in the neutrons irradiated trench-isolated Low Gain Avalanche Diodes (TI-LGADs). This is extension of the previous research on non-irradiated TI-LGADs where an extraordinary large signal was generated without external stimulation (by laser) above a certain bias threshold. Here, the findings related to the impact of the radiation-induced defects and temperature on the ghost signals is discussed. In addition, comparison of double trench (2TR) LGADs with single trench (1TR) LGADs and standard p-type-intrinsic-n-type diodes (PINs) demonstrates the influence of the trenches configuration and gain layer on the ghost phenomenon.

Developing novel memristive systems aims to implement key principles of biological neuron assemblies – plasticity, adaptivity, and self‐organization – into artificial devices for parallel, energy‐efficient computing. Solid‐state memristive devices, such as crossbar arrays and percolated nanoparticle (NP) networks, already demonstrate these properties. However, closer similarity to neural networks is expected from liquid‐state systems, including polymer melts, which remain largely unexplored. Here, the resistive switching in silver/poly(ethylene glycol) (Ag/PEG) nanofluids, prepared by depositing gas‐aggregated Ag NPs into PEGs of varying molecular mass, is investigated. These systems form long‐range conductive NP bridges with reconfigurable resistance states in response to an electric field. The zeta‐potential of Ag NPs and molecular mobility of PEG determine the prevalence of low resistance (ohmic) state, high resistance states (poor conductance) or intermediate transition states governed by space‐charge‐limited conduction or electron tunneling. The occurrence of these states is given by the interparticle gaps, which are determined by the conformation of PEG molecules adsorbed on the NPs. It is presented, for the first time, an equivalent circuit model for the Ag/PEG system. These findings pave the way to adopt polymer melts as matrices for neuromorphic engineering and bio‐inspired electronics.

3D electron crystallography has emerged as a method with great potential for the structure determination of small molecules and macromolecules complementing traditional single-crystal X-ray crystallography and powder X-ray diffraction (PXRD). It offers the unique capability of determining the structures of small molecules and macromolecules from micro- and nanocrystals. In this study, using 3D electron diffraction (3DED), we determined the single-crystal structure of commercially sourced arginine directly from its bottle. The 3DED analysis of micro-sized single crystals identified two distinct forms: the L-arginine enantiomer and the racemic mixture DL-arginine. At the time of writing, neither the Cambridge Structural Database nor the Crystallographic Open Database contain a single-crystal structure of isolated L-arginine (sum formula C6H14N4O2), which has been solved in this work by 3DED. We also present a comparison of the structures of these molecules solved by 3DED and PXRD.

Abstract Ultra-intense laser pulses can create sufficiently strong fields to probe quantum electrodynamics effects in a novel regime. By colliding a 60 GeV electron bunch with a laser pulse focussed to the maximum achievable intensity of 1023 W cm−2, we can reach fields much stronger than the critical Schwinger field in the electron rest frame. When the ratio of these fields χ e ≫ 1 we find that the hard ( > 25 GeV) radiation from the electron has a substantial contribution from spin-light. 33% more photons are produced above this energy due to spin-light, the radiation resulting from the acceleration of the electron’s intrinsic magnetic moment. This increase in high-energy photons results in 14% more positrons produced with energy above 25 GeV. Furthermore, the enhanced photon production due to spin-light results in a 46% increase in the electron recoil radiation reaction. These observable signatures provide a potential route to observing spin-light in the strongly quantum regime ( χ e ≫ 1 ) for the first time.