Search results for "synchrotron"
showing 10 items of 307 documents
Brewster angle microscopy and X-ray GID studies of morphology and crystal structure in monolayers of N-tetradecyl-γ,δ-dihydroxypentanoic acid amide
1997
First-order phase transitions from the low-density fluidlike phase to the condensed phase of monolayers of N-tetradecyl-γ,δ-dihydroxypentanoic acid amides at the air−water interface have been studied by π−A isotherms, Brewster angle microscopy (BAM), and synchrotron X-ray grazing incidence diffraction (GID). The thermodynamic differences between enantiomeric and racemic monolayers are too small to be measured. However, chiral discrimination is observable in the macroscopic domain morphology by BAM. The domains of the condensed phase grow dendritically. The characteristic shapes of domains of the pure S and R enantiomers are mirror images of each other. The domains of the racemic mixture are…
Valence bands of poly(methylmethacrylate) and photoion emission in vacuum ultraviolet region
1992
Photoion and photoelectron yields were measured for poly(methylmethacrylate) in the photon energy region of 8–40 eV using synchrotron radiation. Further, the valence‐band structure was investigated with ultraviolet photoelectron spectra and valence effective Hamiltonian calculations. A significant difference was observed between the photon energy dependencies of photoion and photoelectron yields. The threshold energy for photoion emission was found to be 10.5 eV, while that for photoelectron emission was 8.5 eV, indicating holes created near the valence‐band top do not contribute to the ion emission. At the higher‐energy region, the ion emission efficiency was found to be enhanced in the ph…
Astringency and the interactions between a human salivary proline-rich protein and tannins
2015
International audience
Self-assembly mechanism of nanoparticles of Ni-based Prussian Blue analogues at the air/liquid interface: a synchrotron X-ray reflectivity study.
2015
Prussian Blue analogue (PBA) nanoparticles can be self-assembled at air/liquid interfaces to build novel materials with interesting magnetic features. Herein, we study the influence of the size of PBA Cs0.4 Ni[Cr(CN)6 ]0.9 and K0.25 Ni[Fe(CN)6 ]0.75 nanoparticles on the self-assembly behavior by synchrotron X-ray reflectivity. Both nanoparticles show similar Z-potential values. The phospholipid dipalmitoylphosphatidylcholine and the amino surfactant dimethyldioctadecylammonium have been used as Langmuir monolayers to anchor the PBA nanoparticles and study the interplay of forces directing the self-assembly of the nanoparticles at the surfactant/liquid interface. Whereas Cs0.4 Ni[Cr(CN)6 ]0.…
A synchrotron radiation X-ray scattering study of aqueous solutions of native DNA
1999
Synchrotron radiation small-angle X-ray scattering (SAXS) was used to investigate solutions of native DNA at different ionic strengths and temperatures. The mass per unit length, radius of gyration of the cross-section of DNA and apparent second virial coefficient (A2) were obtained from Zimm plots in the rodlike particle approximation. The values of A2 obtained in this way are positive and almost constant indicating that the repulsive interactions still influence the scattering patterns at resolutions as high as 5-8 nm. SAXS measurements in continuous temperature scans indicate that the rod approximation is valid over a wide temperature range during DNA melting and confirm that the rodlike…
Advances in contrast variation for macromolecular structure determination by polarized neutron scattering and anomalous dispersion of synchrotron X-r…
1988
Contrast variation for macromolecular structure determination is usually achieved by isomorphous replacement of 1-H by 2-H (D) using small-angle neutron scattering (SANS). This is particularly easy in aqueous solvents. By adding heavy water the contrast of dissolved proteins, nucleic acids and membranes changes drastically. It is the region inaccesible to solvent molecules, which acts as a label. Measurements of the scattering intensity at three different scattering densities of a solvent yields the three basic scattering functions. The contrast dependence of the radius of gyration receives particular interest. More recently smaller labels have been used. Their dimensions are smaller than t…
Study of the long-period changes in samples of isotactic poly(propylene) obtained by quenching from the melt and subsequent annealing at different te…
1997
The structural modifications induced in samples of isotactic poly(propylene) obtained by quenching from the melt at 100°C/s and subsequently annealed at 40, 60 and 80°C for different annealing times have been studied using simultaneous wide-angle and small-angle X-ray scattering at the synchrotron radiation source of DESY. The occurrance of two different long-period values is demonstrated. These values are related to the mesomorphic phase, existing in the starting quenched material, and to the α-monoclinic one, which settles during the annealing process, respectively.
Photoluminescence in gamma-irradiated alpha-quartz investigated by synchrotron radiation
2004
Abstract We report an experimental investigation of the photoluminescence, under excitation by synchrotron radiation within the absorption band at 7.6 eV , induced in γ-irradiated α-quartz. Two emissions centered at 4.9 and 2.7 eV are observed at low temperature: the former decreases above 40 K , whereas the second band exhibits an initial slight increase and its quenching is effective above 100 K . Furthermore, the decay kinetics of both emissions occur in a time scale of nanoseconds: at T=17.5 K we measured a lifetime τ∼1.0 ns for the photoluminescence at 4.9 eV and τ∼3.6 ns for that at 2.7 eV . These results give new insight on the optical properties associated with defects peculiar of c…
Luminescence and ultraviolet excitation spectroscopy of SrI2 and SrI2:Eu2+
2013
Abstract We report measurements of luminescence and its ultraviolet excitation spectra in SrI2 and SrI2:Eu2+ at temperatures of 10 and 300 K. Attention is focused on determining the exciton energy and its temperature shift from features of the excitation spectra and limits placed by absorption spectroscopy on a 120 μm thin crystal, on observation of a broadened Eu emission band attributed to trace Eu associated with oxygen in nominally undoped crystals, and on adding observations concerning the 3.4 eV band at low temperature attributed by Pustovarov et al. to the self-trapped exciton.
Surface magnetism studied by photoelectron spectromicroscopy with high spatial and time resolution
2004
Abstract Photoemission electron microscopy (PEEM) is widely used for the study of magnetic surfaces and thin films. Ferromagnetic and antiferromagnetic microstructures are investigated exploiting magnetic circular and linear dichroism in the soft X-ray range using tuneable synchrotron radiation. Local dichroism spectroscopy gives access to magnetic moments of the elements in compounds or multilayer materials. Beyond these achievements, the method bears a high future potential with respect to an increased lateral resolution via aberration correction of the electron optics and a high time resolution in the 100 ps range for the study of dynamic processes. In addition, photoelectron spin polari…