Neutron scattering pulsed

We finish this section by comparing our results with NMR and incoherent neutron scattering experiments on water dynamics. Self-diffusion constants on the millisecond time scale have been measured by NMR with the pulsed field gradient spin echo (PFGSE) method. Applying this technique to oriented egg phosphatidylcholine bilayers, Wassail [68] demonstrated that the water motion was highly anisotropic, with diffusion in the plane of the bilayers hundreds of times greater than out of the plane. The anisotropy of... 

ISIS is only one pulsed source available for the study of liquids. Both the USA and Japan have facilities similar to SANDALS and GEM for studying liquids, but with slightly lower neutron intensity in the forms of the IPNS (Intense Pulsed Neutron Source) at the Argonne National Eab. on the instrument GEAD, and the KEK Neutron Scattering Eacility (KENS) on the instrument ELit II, respectively. 

Lateral diffusion of phospholipids in model membranes at ambient pressure has been studied over the years by a variety of techniques including fluorescence recovery after photobleaching (FRAP), spin-label ESR, pulse field gradient NMR (PFG-NMR), quasielastic neutron scattering (QENS), excimer fluorescence and others.In general, the values reported for the lateral diffusion coefficient (D) range from 10 to 10 cm /s in the... 

In order to determine the dynamics of atoms we have to carry out an inelastic neutron scattering measurement. With a reactor source this can be done with a triple-axis spectrometer, which has an analyzer crystal. Tripleaxis refers to the three axes for the monochromator, sample, and analyzer, all moving independently and controlled by a computer. With a pulsed source we use a mechanical chopper, which is a rotating cylinder with a hole perpendicular to the rotating axis that allows neutrons with a chosen range of velocity to go through. The neutrons scattered by the sample are detected... 

NRA ns pulsed fast neutrons (0.5—4 MeV), broad energy spectrum (n, n) Elastically and resonantly scattered neutrons Nanosecond pulsed (d, Be) accelerator, with Ed < 4 MeV H, O, C, N (others)... 

Windsor CG (1981) Pulsed neutron scattering. Thylor and Francis, London... 

C. G. Windsor, Pulsed Neutron Scattering , Taylor and Francis, London, 1981 Neutron Scattering at a Pulsed Source , eds. R. J. Newport, B. D. Rainford and R. Cywinski, Hilger, Bristol, 1988. 

CCD = charge-coupled device IHIs = interligand hypervalent interactions ILL = Institut Lane-Langevin INS = inelastic neutron scattering IPNS = intense pulsed neutron source LINAC = linear accelerator MaNDi=macro-molecular neutron diffractometer NiMH=nickel-metal OPAL = open pool Australian light-water reactor hydride SANS = small-angle neutron scattering SNS = spallation neutron source. 

C. G. Windsor, Pulsed Neutron Scattering , Taylor and Francis, London, 1981. 

Gives an overview of neutron scattering methods from both pulsed and reactor sources. Also provides some experimental examples. 

R. Pynn, The Mathematical Foimdations ofNeutron Scattering, 1990, http //www./as.org/sgp/othergov/ e/lanVphts/00326652.pdf. A beginners text on the mathematical foimdations of neutron scattering primarily from pulsed sources. 

J. Z. Larese, Neutron Scattering Investigations of the Dynamics of Thin Films Adsorbed on Solid Surfaces, Materials Research Using Cold Neutrons at Pulsed Neutron Sources, [Proceedings] , Argonne, Aug. 25-26, 1997, 1999, p. 57. 

Diffusional motion. Many rotational and translational diffusion processes for hydrocarbons within zeolites fall within the time scale that is measurable by quasielastic neutron scattering (QENS). Measurements of methane in zeolite 5A (24) yielded a diffusion coefficient, D= 6 x lO" cm at 300K, in agreement with measurements by pulsed-field gradient nmr. Measurements of the EISF are reported to be consistent with fast reorientations about the unique axis for benzene in ZSM-5 (54) and mordenite (26). and with 180 rotations of ethylene about the normal to the molecular plane in sodium zeolite X (55). Similar measurements on methanol in ZSM-5 were interpreted as consistent with two types of methanol species (56). 

Sample solutions were prepared by dissolving into D2O Li Cl (a null mixture of Li and Li) and Li Cl for Li-enriched solutions, and Li Cl and Li Cl for Cl-enriched solutions. The sample solution was sealed into a Ti-Zr null alloy cell with inner diameter of 8 mm. Pulsed neutron diffraction measurements were made with HIT at KENS, Japan, and with SANDALS at ISIS, UK. Neutron scattering measurements were also made for background, an empty can, and a vanadium rod. The observed neutron... 

A. Comparison of Self-Diffusion Coefficients Determined by Pulsed-Field Gradient NMR and Quasi-elastic Neutron Scattering... 

The development of high fluxes of low-energy neutrons from pulsed accelerator sources, such as IPNS at Argonne National Laboratory (USA), KEK (Japan) and, especially, ISIS at Rutherford Appleton Laboratory (UK) provides a most suitable probe for studies of the vibrational dynamics of hydrogenous materials. The advantages of neutron scattering for the study of molecular dynamics stem from their remarkable properties. 

Although much of the pioneering work and reputation of neutron scattering has been based on reactor sources, in recent years through primarily the contribution from ISIS, the potential of accelerator based pulsed neutron sources is being increasingly recognised. 

Mesoporous structures are commonly characterized with diffraction, electron microscopy methods [14], and gas sorption techniques. The ensemble diffusion behavior of small molecules has been examined with pulsed-field gradient NMR spectroscopy [15] and neutron scattering [16]. Here, we are interested in techniques which give a more direct access to the real structure of the mesoporous host and to the dynamics on a single-molecule basis, and thus reveal structural and dynamic features which are not obscured by ensemble or statistical averaging as in conventional techniques. 

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