Search results for " Neutron scattering"
showing 10 items of 205 documents
Mesoscopic structure of marble determined by combined USANS and SANS
2006
Marbles, carbonatic (i.e. calcitic–dolomitic) rocks deriving from the metamorphic evolution of previous carbonates, are often rather similar to each other in many respects (i.e. mineralogical, physical–structural and chemical), and thus difficult to identify. In search for a diagnostic method to provenance marbles, we have selected a limited number of Italian white marbles representing a wide array of metamorphic (i.e. thermal) levels. The mesoscale structural arrangement of these samples was derived by means of combined Ultra Small Angle and Small Angle Neutron Scattering experiments. The parameters of the model used to fit the data have been correlated with the metamorphic history of the …
On the use of grazing-incidence small-angle X-ray scattering (GISAXS) in the morphological study of ion-implanted materials.
2004
Grazing-incidence small-angle X-ray scattering has become a widely used technique for the morphological analysis of surface systems. Here it is show how this technique can be applied to a buried system, like metallic clusters in glass obtained by ion implantation. The optimization of the data-collection geometry is described as well as the details of the quantitative data analysis. An experimental example on Cu + Au-implanted glasses shows the potentiality of the technique.
First measurement of the electric formfactor of the neutron in the exclusive quasielastic scattering of polarized electrons from polarized 3He
1994
Abstract A first measurement of the asymmetry in quasielastic scattering of longitudinally polarized electrons from a polarized 3 He gas target in coincidence with the knocked out neutron is reported. This measurement was made feasible by the cw beam of the 855 MeV Mainz Microtron MAMI. It allows a determination of the electric formfactor of the neutron G E n independent of binding effects to first order. At Q 2 =0.31 ( GeV /c) 2 two asymmetries A ∥ ( S He ∥ q ) and A ⊥ ( S He ⊥ q ) have been measured giving A ∥ =(−7.40±0.73)% and A ⊥ =(0.89±0.30)% . The ratio A ⊥ / A ∥ is independent of the absolute value of the electron and target polarization and yields G E n =0.035±0.012±0.005.
About entangled networks of worm-like micelles: a rejected hypothesis
1996
We report new results from small-angle neutron scattering on d(1 2)-cyclohexane/lecithin/water micellar solutions performed as a function of the water content (w(o)), temperature (T) and dispersed phase volume fraction (phi). The data from dilute samples are interpretable in terms of the existence of giant cylindrical reverse micelles and are well fit with a core-shell model (that provides the micelle structure and dimensions) with values of 28 and 45 Angstrom for the inner core and the outer shell radii, almost independent on temperature and concentration. Such a result could appear consistent with the current idea that worm-like micelles are living polymers. On the contrary, the appearanc…
The Combined Ultra-Small- and Small-Angle Neutron Scattering (USANS/SANS) Technique for Earth Sciences
2009
The extension of the well-known Small-Angle Neutron Scattering (SANS) technique to Ultra-Small Angles (USANS) provides a unique tool for studying hierarchical structures ranging in size from nanometers to micrometers. Hierarchical structures are common for many natural and man-made materials, which show multi-level morphology (atoms–molecules–aggregates–agglomerates), in other words, are made up of structural units encompassing the atomic, molecular, micro- and macroscopic length scales. Combining USANS and SANS data can provide complete structural information for complicated polydisperse systems, allowing the determination of their complex morphology and hence has been successfully applied…
Deep inelastic scattering in the dipole picture at next-to-leading order
2017
We study quantitatively the importance of the recently derived NLO corrections to the DIS structure functions at small x in the dipole formalism. We show that these corrections can be significant and depend on the factorization scheme used to resum large logarithms of energy into renormalization group evolution with the BK equation. This feature is similar to what has recently been observed for single inclusive forward hadron production. Using a factorization scheme consistent with the one recently proposed for the single inclusive cross section, we show that it is possible to obtain meaningful results for the DIS cross sections.
Small angle neutron scattering studies of critical phenomena in a three-component microemulsion
2007
Critical density fluctuations of a ``water-in-oil`` microemulsion consisting of water, benzene, and BHDC (benzyldimethyl-n-hexadecyl ammonium chloride) were observed near the phase boundary by SANS. Observed profiles were well described by product of a form factor of spherical droplets and a structure factor, consisting of a term describing the inter-droplet correlations and also an Ornstein- Zernike component describing the droplet density fluctuations. Allowance was also made fro droplet polydispersity,though the width of the distribution turned out to be very small (1-2%). Observed temperature dependence of osmotic compressibility was fitted using the crossover function proposed by Belya…
Isostructural phase transition, quasielastic neutron scattering and magnetic resonance studies of a bistable dielectric ion-pair crystal [(CH3)2NH2]2…
2019
We have synthesised and characterised a novel organic–inorganic hybrid crystal, [(CH3)2NH2]2KCr(CN)6. The thermal DSC, TMA, DTG and DTA analyses indicate two solid-to-solid structural phase transitions (PTs). According to the X-ray diffraction experiments, the first PT at 220 K is isostructural, since it does not involve a change of the space group. This transition occurs between the states, where the (CH3)2NH2+ cations are orientationally disordered and ordered (frozen). The other reversible PT at 481 K leads to a melt-like phase similar to the one observed in plastic crystals or polar liquids. Dielectric spectroscopy has been used to characterise the switching properties of the dipole mom…
Diffusive motions in HD films physisorbed on graphite
2003
Abstract High-resolution quasielastic neutron scattering was used to study diffusive motions in two-dimensional liquid and solid phases of deuterium hydride submonolayers adsorbed on graphite (Papyex). For the first time it could be unambiguously clarified that the novel reentrant fluid phase at the commensurate–incommensurate transition has the character of a viscous fluid.
LaAg x In1?x
1980
The phonon dispersion of LaAg x In1−x (x=1, 0.89, 0.8) has been studied by inelastic neutron scattering in the cubic high temperature phase. A soft mode behaviour was observed at theM-point. The doubling and the cubic to tetragonal deformation of the elementary cell was observed through the phase transition. The measurements of the elastic constants were extended to 450 K and their magnetic field dependence was investigated.