Synchroton radiation

Viovy,J.L. and Monnerie, L. Fluorescence Anisotropy Technique Using Synchroton Radiation as a Powerful Means for Studying the Orientation Correlation Functions of Polymer Chains. Vol. 67, pp. 99—122. 

Direct in situ X ray (from synchroton radiation) adsorption measurements (EXAFS) (Hayes et al., 1987, Brown et al., 1989) permit the determination of adsorbed species to neighboring ions and to central ions on oxide surfaces in the presence of water. Such investigations showed, for example, that selenite is inner-spherically and selenate is outer-spherically bound to the central Fe(lll) ions of a goethite surface. It was also shown by this technique that Pb(II) is inner-spherically bound to 5-AI2O3 (Chisholm-Brause et al., 1989). 

The far infrared region. The standard infrared (IR) light source used to be the glowbar, but in recent years it was realized that synchroton radiation... 

Demonstration of surface shifts in the nonmetal levels, i.e. in the C Is and N Is levels, was not feasible in these first efforts. These levels are located considerably deeper in energy and were inaccessible. Recent developments in synchroton radiation instrumentation,15 however, allow high resolution core level studies to be performed involving these levels.16-20 The first such study was carried out on the (100) and (111) surfaces of VC16 and a surface shifted C Is level was clearly observed (Figure 25.2). A C Is... 

Five crystal modifications of Aspartame are known (Ajinomoto 1983 Hatada et al. 1985 Nagashima etal. 1987 Kishimoto andNaruse 1988 Tsuboi etal. 1991 Furedi-Milhofer et al. 1999). A number of analytical methods have been used recently to characterize three of them two hemihydrate polymorphs and a dihemihydrate (Leung etal. 1998a,b, Zell etal. 1999). The crystal structure of one of the hemihydrate forms, known as Form I, was published earlier (Hatada etal. 1985). More recently, synchroton radiation was used to determine the structure of the low humidity form (denoted Form Ib by the authors), with an asymmetric unit comprised of three aspartame molecules and two water molecules (Meguro et al. 2000). 

Direct evidence for inner-sphere complexes comes from spectroscopic methods, for example, Fourier transform infrared spectroscopy (Figure 9.11) Biber and Stumm, 1994 Hug and Sulzberger, 1994 Tejedor-Tejedor and Anderson, 1986) and direct in situ x-ray (from synchroton radiation) absorption measurements (EXAFS) (Brown et al., 1989, Charlet and Manceau, 1993 Hayes et al., 1978). For a general review, see Johnston et al. (1993). 

It is hoped that further studies using a wider variety of photon energies, as provided by synchroton radiation, may help identify the degree to which inferences from intensity changes are valid. 

Schematically, the studies proceed as follows the white synchroton radiation beam is at the same time focused and dispersed in energy by a curved crystal. The sample is located at the focus point, and the detection is done by a positon-sensitive detector, such as a photodiode array, that is able to withstand a very high photon flux. Therefore, the relationship Bragg angle-energy of the diffracted beams is translated into a correlation energy-position in the detector. In the best cases, like an elemental copper foil, only a few milliseconds are needed to acquire an EXAFS spectrum.

Synchroton radiation has been employed as a spectral source for a study of the absorption of HCN and DCN in the wavelength range 80—120nm. A vacuum-u.v. spectrophotometer for absorptions in the region 105—200 nm has been described. Solid-, liquid-, and gas-phase samples could be analysed at temperatures from —200 to 100 °C and at pressures between 0 and 150 atmospheres. The absorption spectrum of tra j-di-imide in the vacuum-u.v. has been measured. First-derivative u.v. spectroscopy has been employed in the analysis of Watts nickel plating solutions for trace amounts of saccharin. Impurity levels of 0.1 p.p.m. have been recorded. A wavelength modulated derivative spectrophotometer with a multi-pass absorption cell has been developed for the automatic analysis of atmospheric pollutants. Traces of SOj, NO, and NO2 were detected with limits of 15, 13, and Sp.p.b., respectively. A double-beam single-detector absorption spectrometer has been constructed. Independence... 

Kim KJ (1985) Characteristics of Synchroton Radiation. In X-ray Data Booklet. Vaughn D (ed). Lawrence Berkeley Laboratory PUB-490... 

B.A. Bunker, K.M. Kemmer, P. Dutta, R.S. Duran, J. Kaduk CP521, Synchroton Radiation Instrumentation 11" U.S. National Conference, ed. P. Pianetta, et al., 419-422 (American Institute of Physics, New York, 2000). 

Scattering experiments with synchroton radiation at A = 154 pm showed only small annealing effects proving the poor crystallizability of the COP the well known block structures of PET and PHB, however, were clearly identified (Figure 9.17). Pure poly-PHB is highly crystalline and shows a slight increase of the lattice distances with increasing temperature (thermal expansivity) with almost no additional crystallization. 

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