Diffusion neutron spectroscopy

The platinum contents were measured using Neutron Activation Analysis. The Pt-containing materials and the parent catalyst support were characterized by Na adsorption-desorption and X-ray diffraction. Furthermore, the impregnated solids have been characterized by UV-Vis Diffuse Reflectance spectroscopy and Temperature Programmed Reduction (TPR). 

Lett. 60(12), 1134-1137 (1988). doi 10.1103/PhysRevLetL60.1134 L.F. Rojas-Ochoa, S. Romer, F. Scheffold, P. Schurtenberger, Diffusing wave spectroscopy and small-angle neutron scattering from concentrated colloidal suspensions. Phys. Rev. E 65(5), 051403 (2002). doi 10.1103/PhysRevE.65.051403... 

Other observations at this and other laboratories provides strong supporting evidence for the existence of ordering. Neutron-spectroscopy studies of Y(H)Dq by Anderson et al. (1986) show a soft anharmonic potential along the c-axis and a low-temperature splitting of the c-axis vibrational modes. Further refinements for the Y -I- H system by Anderson et al. (1988) show that hydrogen diffusion between adjacent... 

The last but not the least advantage of neutron spectroscopy is its ability to measure long-range translational motions over short distances, of the order of a few unit cells. Therefore diffusion coefficient measurements are free of spurious effects due to defects in the crystals. 

The application of neutron spin-echo spectroscopy to the analysis of the slow dynamics of biomolecules is still in its infancy, but developing fast. The few published investigations either pertain to the diffusion of globular proteins in solution [332-334] or focus on the internal subnanosecond dynamics on the length scale, <10 A as measured on wet powders [335,336]. The latter regime overlaps with other quasi-elastic neutron scattering methods as backscattering and TOE spectrometry [337-339]. 

These speciation concepts are illustrated in Fig. 3 for the idealized basal-plane surface of a smectite, such as montmorillonite. Also shown are the characteristic residence-time scales for a water molecule diffusing in the bulk liquid (L) for an ion in the diffuse swarm (DI) for an outer-sphere surface complex (OSQ and for an inner-sphere surface complex (ISC). These time scales, ranging from picosecond to nanosecond [20,21], can be compared with the molecular time scales that are probed by conventional optical, magnetic resonance, and neutron scattering spectroscopies (Fig. 3). For example, all three surface species remain immobile while being probed by optical spectroscopy, whereas only the surface complexes may remain immobile while being probed by electron spin resonance (ESR) spectroscopy [21-23]. 

A fit-for-purpose estimate of the individual activities is needed for waste disposal purposes and calculation of neutron activation of precursors is often the simplest method, where contamination is unimportant. For H, the concentration of the Li precursor is required. The mobile nature of is a complicating factor since, in principle, it may remain in situ or diffuse within the bulk material. The aim of this work was to provide some answers to the above questions by determining the concentrations of Li in reactor steels and to compare the predicted levels of with values measured in reactor surveillance specimens. Preliminary attempts to measure Li in reactor steels by ICP-OES (inductively coupled plasma - optical emission spectroscopy) were not successful and... 

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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