[en] Using a molecular fluorine laser at 157 nm foxing stains were removed successfully from a 16th century old paper. Laser cleaning of stains and foxing from old paper manuscripts is far more effective at 157 nm in comparison to different wavelengths without leaving any yellowish after-effect on the paper. This is because at 157 nm illumination of old paper, complete bond breaking of all the organic molecules of the paper is taking place. Mass spectroscopy at 157 nm and for moderate laser intensities up to 1 mJ/cm² of old paper suffering from foxing indicate organic matter disintegration to small photofragments atomic, diatomic or triatomic, which are flying apart with supersonic speed. In addition high spatial resolution energy dispersive X-ray system (EDXS) analysis over the effected areas indicate the presence of iron, suggesting that biological activity is taking place preferentially in paper areas containing iron

[en] The influence of the magnetic field and the water flow on the crystal form of calcium carbonate precipitated from low-concentration water solution was followed systematically. By changing the strength of the field, the calcite/aragonite/vaterite ratio varied. The crystal form and the particle size distribution of the precipitated calcium carbonate were determined by using X-ray analyses and transmission electron microscopy (TEM). A simple hydrodynamical model, using the Navier-Stoke's and Maxwell's equations, predicts that there is a strong energy coupling and transfer between turbulent flow and the magnetic fields, which can be amplified to high values. Since the formation of aragonite is enhanced in the presence of magnetic field, scaling is prevented in turbulent flow

[en] Transmission electron microscopy was used to investigate the cluster formation of trivalent rare earth (RE) ions in wide band gap dielectric crystal hosts with atomic resolution. Various defects and areas with variation in chemical composition with dimensions of ∼5 nm were observed. This finding sets the limit in the value of the refractive index, and thus in the optical quality of these crystals

[en] Lithography at 157 nm using F₂ laser is the next step after 193 nm for ULSI fabrication with dimensions below 50 nm. However, there are problems related to the development of the 157 nm technology, the most important being the design of photoresists with suitable absorption at 157 nm and low outgassing. On the other hand, high-resolution capabilities of resist depend on the surface roughness and its modification following 157 nm illumination of the resist. In this communication, a copolymer of ethyl-polyhedral oligomeric silsesquioxane (ethyl-POSS) and tert-butyl methacrylate (TBMA) was evaluated for surface homogeneity, before and after exposure to 157 nm at different concentrations of the homopolymers. Surface roughness depends on the chemical composition of the resist, and atomic force microscope (AFM) images of exposed areas indicate accumulation of matter at the edge of the boundaries between exposed and non-exposed areas

[en] Soft X-ray contact microscopy (SXCM) enables the study of the ultrastructure of living hydrated specimens, without the need of dehydration or any other chemical pretreatment, by using suitable pulsed X-ray sources such as laser plasmas. The successful imaging of biological specimen requires the development of sensitive photoresist materials for image recording; these should have capabilities of high-resolution lithography and an extended grey scale. A very sensitive photoresist, used for the first time in SXCM, enabled the biological imaging with the specific source in single-pulse experiments in the water window spectral range. This photoresist is an epoxy novolac-based chemically amplified photoresist (EPR), which has been proven capable of resolving subtenth-micron features. The photoresist response was at least two orders of magnitude 'faster' than polymethyl methacrylate (PMMA), which is the standard resist used so far in SXCM. Atomic force microscopy (AFM) and scanning electron microscopy of the biological specimen images recorded in the resist clearly showed the flagella of the motile green alga, suggesting a lateral resolution better than 100 nm. The resist was also capable of providing height features, as small as 20 nm, in AFM depth profiles and discriminating the flagella intersection areas

[en] The investigation of the optical and magnetic properties of the rare earth ions in wide band gap fluoride dielectric crystals could trigger a new variety of applications using high excited electronic states. By applying laser-induced fluorescence spectroscopy in the vacuum ultraviolet (VUV) region of the spectrum (100-200 nm), it was found strong emission in the VUV and UV spectral regions due to the strong dipole 4f^n-15d→4fⁿ interconfigurational transitions of rare earth (RE) ions in wide band gap fluoride crystals. The emitted radiation is highly directional suggesting a strong paramagnetic response of the 4f^n-15d electronic configuration following VUV laser excitation at 157 nm. In addition, the concentration of the Pr³⁺ and Tm³⁺ ions in KY₃F₁₀ and CaF₂ crystal hosts can be accurately evaluated by measuring the magnetic moment of the Pr³⁺ and Tm³⁺ ions, using the vibrating sample magnetometer method, in a non-destructive way for the first time to our knowledge. Since the efficiency of the laser crystals doped with trivalent RE ions depends on the degree of the homogeneous distribution of the concentration of the trivalent RE ions over the crystal volume, the method can be used to evaluate the quality of the laser crystals

[en] Laser induced fluorescence of the mercury clusters Hg₂ and Hg₃ in the spectral range between 300 nm to 510 nm has been obtained from the dissociation of HgBr₂ at 7.88 eV (157.5 nm) with an F₂ molecular laser, together with fluorescence from mercury atomic transitions from highly excited states. The excitation process involves two photon absorption which dissociates the molecule at 15.76 eV total photon energy with the subsequent formation of the metallic clusters. (orig.)

[en] The Raman spectra of tetragonal CaMoO₄ (scheelite structure, C_4h⁶ space group) have been measured in the temperature range 12-1300 K. At high temperatures, the frequency and linewidth of all Raman-active phonons vary almost linearly with temperature, indicating that the three-phonon decay processes are dominant over the four-phonon ones. All Raman phonons display normal negative (δω/δT) slopes throughout the temperature range, except for the lowest-frequency B_g phonon at 111.5 cm^-1 which is almost temperature independent in the region 12-400 K, but then for T > 400 K it shows a slight (normal) softening with temperature. The reduced (δω/δT)/ω slopes of the internal modes (vibrations of atoms within the tetrahedral MoO₄^2- units) are an order of magnitude smaller than the respective slopes of the external ones (pure lattice modes). There are no discontinuities or sharp changes of slope in the ω(T) plots, implying that CaMoO₄ remains stable over the entire temperature range. Combining the temperature-dependent Raman data of this work and the previously reported pressure-dependent Raman data on this crystal (Christofilos D, Kourouklis G A and Ves S 1995 J. Phys. Chem. Solids 56 1125), as well as the thermal expansion coefficient β(T) and compressibility K(T) data, it has been possible to separate and evaluate quantitatively the volume (expansion) Δ_vol^ω and the pure temperature (anharmonic) Δ_anh^ω contributions to the total Δ_tot^ω shift of phonons with temperature. It has been found that for most phonons at high temperatures, the volume effect is greater than the pure temperature one, thus indicating that most of the bonds in CaMoO₄ are predominantly ionic in character. (author)

[en] Sm-Fe-Ta-N core-shell (CS) nanospheroids were fabricated from hot liquefied nanodroplets by 157 nm pulse laser deposition in nitrogen gas. The Sm_13.8Fe_82.2Ta_4.0 intermetallic alloy was used as the target. At low laser energy (20 mJ), spherical CS of 1-35 nm radius were fabricated on a Si/Ta substrate forming uniform films. The small nanodroplets were grown in the plume from the gas phase, and the larger ones (>50 nm radius) from the target's hydrodynamic ejection. The critical radius of the droplets and their surface energy per unit area was found to be 7.5 nm and 3.8 μJ/cm² respectively. A number of CS solidified in the plume and consist of 2.5-5 nm radius crystalline nucleus surrounded by a <35 nm radius amorphous spherical shell. This structure prevents the oxidization of the crystalline nucleus because oxidization is confined on the surface of the CS. Furthermore, multi-crystalline nanodomains (embryos) were identified in a single CS from both homogeneous and heterogeneous nucleation. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

[en] Transmission electron microscopy, energy dispersive X-ray spectroscopy, and high-resolution scanning-transmission electron microscopy, with electron beam sizes ranging from 2 to 50 nm, were used to investigate the spatial distribution and homogeneity of doped Tm³⁺ ions in CaF₂ host matrices with atomic resolution, in solid crystals grown from melts using the Bridgman-Stockbarger method. With the smallest size electron beam available of 2 nm, it was found that the Tm³⁺ ions were distributed inhomogeneously at the host sites. They took the form of sub-nm agglomerations of 3-5 atoms, rather than individual ions and the phase transition layer was 0.1 nm thick. The spatial extend of inhomogeneous Tm³⁺ concentration was 2.6-6 nm and originates from ionic density fluctuations in the liquid phase at the interface layer due to the local electrostatic field at the ionic sites