Beamline

The prepared catalysts were characterized by x-ray diffraction (XRD), N2 adsorption and CO chemisorption. Also, X-ray absorption spectroscopy (XAS) at the Ni K edge (8.333 keV) of reference and catalyst samples was carried out in the energy range 8.233 to 9.283 keV at beamline X18B of the... 

CIPO Beamline, Elettra Photoelectron Imaging for PECD Non-imaging PECD Measurement... 

Accurate experimental determinations require that not only the handedness of the produced light, but its exact degree of polarization, are known. The theoretical performance of an undulator may be in practice be degraded by magnetic defects, and the optical beam can be further depolarized by reflections along the beamline. Again, the dephasing on optical elements can in principle be... 

On an undulator beamline, 54 would normally only be non-zero as a consequence of some defect or optical pollution from some source. The dichroism and asymmetry factor, y, will scale with 3 so that the ideal for PECO measurements would be to have i3 1 and 4 0. 

It is revealing to look at an example of such data in Fig. 12. The UE56/2 beamline has two nominally identical branches with replicated optical paths, but that have been used for different experiments. The measurements show a high degree of circular polarization, [531 > 98%, except near carbon K edge where the polarization reduces, but only on one branch. It is postulated that this is a consequence of carbon contamination on a beamline optic in that branch. These results demonstrate the necessity to be alert to such possible causes of degradation and to perform polarization checks where possible rather than rely on theoretical predictions. 

The SU5 beamline [89] at the Super-ACO synchrotron (LURE, Paris ) employed an electromagnetic undulator to produce fully variable polarization in the VUV region [83, 90, 91]. This beamline was equipped with a gas filter for the suppression of unwanted higher order radiation [92] and had a VUV polarimeter [93] permanently installed just before the experimental chamber that could be rapidly lowered into the beam for polarization determinations. Full polarization analyses had been performed in commissioning, with 53 values ranging from 0.9 to 0.96 for rep and from 0.9 to 0.99 for Icp [93]. The remainder was determined... 

LURE recently closed, but the concept of this beamline is to be reimplemented in the DESIRS beamline under construction at the new Soleil synchrotron outside Paris. 

The circular polarization (CIPO) beamline at the Elettra synchrotron (Trieste, Italy) operates in the VUV-SXR range with radiation from a combination permanent magnet-electromagnetic elliptical wiggler [94, 95]. This does not achieve full circular polarization in the VUV region, but rather an elliptical output with principal axis lying in the horizontal plane (ii > 0, 2 = 0, < 1). 

Unfortunately, in the VUV region no polarimetry data are available, but calculations indicate the degree of circular polarization achieved by the wiggler may be 80%, estimated to be no worse than 70% delivered at the experimental chamber [95, 96]. In PECD experiments, we have calibrated the polarization state by deduction from cross-comparison of results at a few fixed energies previously studied on the SU5 beamline where accurate polarimetry data was available [36]. Because the horizontal magnetic field array in the insertion device is electromagnetic, fast current reversal to switch left- and right-handed elliptical polarizations is possible, with the usual potential benefit for dichroism measurements. 

The reaction on the catalyst surface was followed by in situ i.r. spectroscopy using a Bruker IFS88 FTIR spectrometer for the characterisation of sorbed species and mass spectroscopy for the analysis of gas phase. The state of Pt was further investigated by in situ X-ray absorption spectroscopy (Daresbury, UK, beamline 9.1, transmission mode, Si(220) monochromator, Pt-Lj, edge). Details of catalyst characterisation techniques are reported elsewhere [13,14]. 

Figure 3. Example of XRPD on small Au clusters supported on silica. Total diffraction intensity has been measured with area detector (IP) on BM08-GILDA beamline at the ESRF with A = 0.6211 A and 2min exposure time. Diffraction patterns were collected on Au-supported sample (Exp) and on silica support (Support). Difference patterns, corrected for fluorescence, IP efficiency, etc., are shown (n-Au).

Extended X-ray Absorption Fine Structure (EXAFS) the measurements were mostly made at the Gilda Italian Beamline (equipped with a bending magnet) at the European Synchrotron Radiation Facility in Grenoble (France). 

A monochromatic beam of X-rays with about 1 eV bandwidth is produced by the standard beamline equipment, the undulator and the high-heat-load premonochromator being the most important parts among them. Further monochromatiza-tion down to approximately the millielectronvolt bandwidth is achieved with the high-resolution monochromator. The width of a band of a millielectronvolt, however, is much more than the inherent linewidth of the Fe y-radiation, F 10 eV, or the full range of hyperfine-split Mossbauer lines, A m 10 eV. Yet, NFS is detectable because the coherent excitation of the nuclei is caused in the... 

Table 9.6 List of synchrotron radiation sources which provide dedicated nuclear resonance beamlines for specific isotopes...

Spectroscopic evaluation of the catalysts. The UV-Vis spectra of the Jacobsen Co-salen catalysts were collected in the transmission mode on a CARY-3E UV-Vis spectrophotometer by dissolving the catalysts in epichlorohydria The Co K-edge (7709 eV) X-ray absorption near edge stracture, XANES, of Jacobsen s Co-salen catalyst was collected during the HKR reaction at beamline XIO-C at National Synchrotron Light Source (NSLS), Brookhaven National Lab, Upton, NY. 

The first nuclear microbeam with a spatial resolution of 1 pm was built by Watt et al. (1981), and the first sub-micron instrument was built by Grime et al. (1987). Khodja et al. (2001) have published a description of the nuclear microprobe at the Pierre Sue Laboratory in France, which is a national facility dedicated to microbeam analysis. Its unique facility is that it is capable of analysing radioactive samples by means of a dedicated beamline. Figure 4.1 shows a schematic diagram of the apparatus. 

Each of the two beamlines are focussed by a single electromagnetic quadrupole doublet, and a beam size of about 1 pm2 is achieved with a beam current of approximately 50 pA. Electrostatic deflectors are mounted to permit beam sweeping on the sample both to produce images and to limit heating effects. 

The analysis chamber is such that PIXE, RBS, PIGE, NRA and ERDA are routinely performed simultaneously with the microprobe. A 4-axis micron-level goniometer permits precise positioning. The radioactive beamline enters a shielded... 

The typical experimental setup (here the experiment established at beamline G3/ HASYLAB [12] is shown) is outlined in Figure 5. The white synchrotron radiation is monochromatized by a double crystal monochromator using the Ge (311) reflection... 

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