Centre de Recherche sur les Ions, les Matériaux et la Photonique

This work focused on the mechanical behaviour of flax fibre bundles to understand their response to tensile testing. Flax bundles exhibit the same non-linear behaviour under mechanical stress as elementary fibres. Video recorded tests revealed that during tensile loading, fibre bundles undergo a coupling between tension and rotation. Three different scenarios were identified: pure tension, tension-torsion coupling to failure, and partial tension-torsion coupling ending before specimen failure. Elementary fibre decohesion was also observed during fibre bundle tensile tests. Overall, the tensile behaviour of fibre bundles is influenced by their initial morphology, especially the degree of twist, and the mechanical efficiency of the lamella between the elementary fibres (middle lamella). In addition, the influence of the geometric model used to represent the cross-section on the mechanical properties was investigated using circular and elliptical models. The results show a significant dependence on the geometrical model considered. Therefore, a standardised method for measuring the cross-sectional area of plant fibres is required to enable comparison of results from the literature. • Flax fibre bundles exhibit non-linear tensile behaviour. • Video-recorded tensile tests reveal tension-rotation coupling and fibre decohesion. • Geometric model for cross-section significantly impacts mechanical propertie measurement. • Standardised cross-section measurement is key for reliable property comparisons.

We demonstrate a femtosecond Mamyshev ring oscillator operating near 920 nm, based on W-type index profile double-clad Nd3+-doped polarization-maintaining (PM) fibers. Mode-locking is initiated using an intracavity SESAM to ensure reliable self-starting. This mode-locked fiber laser source delivers up to 7.1 nJ pulse energy at a repetition rate of 10.47 MHz, which is compressed down to 71 fs using a pair of gratings. An amplification stage utilizing optimized Nd-doped large mode area (LMA) fiber increases the pulse energy up to 105 nJ, though this results in longer compressed pulses.

This chapter explores polymer behavior under ionizing radiation, and focuses on synthetic organic polymers, that is, those synthesized from chemical compounds resulting from petrochemistry. It presents the various types of ionizing radiation, the interactions between ionizing radiation and polymers, the resulting defects and the factors influencing the behavior of a given material exposed to ionizing radiation. In the presence of atoms with high atomic numbers, the boundary between the photoelectric effect and Compton scattering is shifted toward high energies, and depending on the atoms present, the photoelectric effect can no longer be ignored. Accelerated ions can interact with target atoms via two mechanisms: elastic collisions with their nuclei or inelastic collisions with their electrons. Concerning the influence of the irradiation environment, the most important factor is the presence or absence of oxygen molecules. Energy transfer phenomena play an important role in polymer evolution under ionizing radiation.

Holmium lasers represent an effective and powerful source of laser radiation in the atmospheric windows in the 2 μm region and they are very attractive due to their possible applications in atmospheric remote sensing [1]. Fluorite-type crystals, such as calcium, strontium and barium fluorides, feature long radiative lifetimes of Ho<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> multiplets and weak non-radiative relaxation due to their low phonon energies. In addition, these crystals benefit from rare-earth ion clustering leading to broadband emission properties. Tm-codoping helps to simplify pumping of Ho-based lasers and improves their robustness. In our previous works, we demonstrated efficient excitation of H03+ ions in CaF2 by diode pumping of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{Tm}^{3+}$</tex> ions (at 785 nm or 1.7 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mu \mathrm{m}$</tex>) [2], [3]. In this study we firstly present promising results obtained with resonant diode pumping of new Tm, Ho- doped strontium and barium fluorites.

The heaviest elements in the periodic table have a low production yield. In order to increase the production yield of the superheavy elements, thicker targets are required than the present molecular plating technique can offer. Therefore, lanthanide thin films, as lighter homologues to the actinides, were prepared by a new electrodeposition method. The trifluoromethanesulfonates (triflates) of the lanthanide salts were dissolved in Dimethylformamide (DMF) and then electrochemically deposited onto substrates of different geometries. These thin films were irradiated with different swift heavy ion beams with energies of over 200 MeV. Thin films were analyzed spectroscopically by Raman and IR measurements before and after irradiation, to investigate chemical changes induced by irradiation.

Context. Ultra-carbonaceous Antarctic micrometeorites (UCAMMs) are carbon-rich micrometeorites. Their organic matter formed in a N-rich environment, possibly via the galactic cosmic ray (GCR) irradiation of ice mantles at the surfaces of small bodies. Nanoscale secondary ion mass spectrometry (NanoSIMS) revealed that UCAMMs exhibit large H, C, and N isotopic heterogeneities at the micron scale. Aims. We aim to investigate the transfer of H, C, and N isotopic heterogeneity from an ice mixture to its ion-irradiation-induced organic residue. The goal of this work is to understand the formation of H, C, and N bulk- and micron-scale isotopic heterogeneities in the organic matter of UCAMMs. Methods. We performed irradiation experiments of isotopically heterogeneous ice films at 10 K, with swift heavy ions to model the irradiation of isotopically heterogeneous icy surfaces via GCR. The irradiated ice mixtures were subsequently annealed to room temperature, which led to the formation of refractory organic residues. NanoSIMS imagery was performed on the organic residues to identify micron-scale H, C, and N isotopic heterogeneity. The ice films consisted of N2-CH4 (9:1) and NH3-CH4 (9:1) ices that contain a thin layer of D-, 13C-, and 15N-labeled species. Results. The irradiation-induced organic residues exhibit micron-scale isotopic anomalies. The transfer of isotopic anomalies from the ice to the organic residue appears to depend on the chemical composition of the ice film. Conclusions. These experiments show it is possible to transfer isotopic heterogeneity that is initially present in cometary ices to refractory organic residues that formed by heavy ion irradiation. Gaseous reservoirs of volatile species with highly fractionated isotopic compositions are predicted to exist in the early Solar System and should coexist under the form of ice mantles at the surface of small bodies at large heliocentric distances. The study of organics in UCAMMs can thus shed light on the composition of N- and C-rich ices at the surface of outer Solar System small icy bodies.

Gas-phase near-edge X-ray absorption mass spectrometry (NEXAMS) was employed at the carbon and oxygen K-edges to probe the influence of a single water molecule on the protonated phosphotyrosine molecule. The results of the photodissociation experiments revealed that the water molecule forms two bonds, with the phosphate group and another chemical group. By comparing the NEXAMS spectra at the carbon and oxygen K-edges with density functional theory calculations, we attributed the electronic transitions responsible for the observed resonances, especially the transitions due to the presence of the water molecule. We showed that the water molecule leads to a specific spectral feature in the partial ion yield of hydrated fragments at 536.4 eV. Moreover, comparing the NEXAMS spectra with the calculated structures allowed us to identify three possible structures for singly hydrated phosphotyrosine that agree with the observed fragmentation and resonances.

X-ray absorption spectroscopy (XAS) and quantum mechanical calculations bear great potential to unravel π stacking side-chain interaction properties and structure in, e.g., proteins. However, core-excited state calculations for proteins and their associated interpretation for π-π interactions are challenging due to the complexity of the non-covalent interactions involved. A theoretical analysis is developed to decompose the core-to-valence transitions into their atomic contributions in order to characterize the π stacking of aromatic amino acids as a function of their non-covalent distance change. Three models were studied as a non-covalent mixed dimers of the phenylalanine, tyrosine and tryptophan amino acids. We found that there are carbon 1s → π* charge transfer transitions associated with the non-covalently paired aromatic amino acids through their side chains. The atomic-centered contributions to the electronic transition density quantify the excited state charge transfer of the pairing amino acid models, highlighting the π stacking interactions between their aromatic side chains.