Synchrotron irradiation

We attempted to use this increase in refractive index in fabricating polyimide optical waveguides. The fabrication of a fluorinated polyimide waveguide by the direct electron beam writing method is described in Section 4.3.2. We also investigated the changes in the refractive index of fluorinated polyimide films by synchrotron radiation. 7 The refractive index at a wavelength of 589.6 nm increased by 1.3% and the thickness decreased by 0.69% for fluorinated polyimide film after 30 min of synchrotron irradiation. From the XPS data the synchrotron radiation leads to production of a fluorine-poor surface. 

Recently von Boehlen et al. (1991) have obtained an improved crystal form of the large (50S) ribosomal subunit of H. marismortui, which diffracts to 3 A resolution, by the addition of 1 mAf Cd2+ to a crystallization medium that contained over 1.9 M of other salts. These improved crystals are isomorphous with the previously reported ones, and, as was the case for the previous crystals, they show no measurable decay after a few days of synchrotron irradiation at cryotemperatures. The new crystals are of adequate mechanical strength. Initial phasing studies by specific and quantitative deriva-tization with super-dense heavy-atom clusters and by real- and reciprocal-space rotation searches are in progress. 

Tomita, M. Hieda, K. Watanabe, R. Takakura, K. Usami, N. Kobayashi, K. Hieda, M. Comparison between the 5nelds of DNA strand breaks and ferrous ion oxidation in a Fricke solution induced by monochromatic photons, 2.147-10 keV. Radiat. Res. 1997,148,490-491. Maezawa, H. Ito, T. Flieda, K. Kobayashi, K. Ito, A. Mori, T. Suzuki, K. Action spectra for inactivation of dry phage T1 after monoehromatic (150-254 nm) synchrotron irradiation in the presence and absence of photoreactivation and dark repair. Radiat. Res. 1984, 98 (2), 227-233. 

Fig. 9.4 a Anion receptors possessing long alkyl chains and b POM images of i Ic, ii 2c, and Hi 3c as mesophases at 170,70, and 196 °C, respectively, upon cooling from Iso. Also shown in bi is the synchrotron XRD pattern of Ic at 120 °C upon coohng from Iso and a proposed Colh model. The XRD by synchrotron irradiation was performed in [42] and the data was basically consistent with the XRD in [35]... 

Synchrotron irradiation of 2,2-dimethylbutane yielded C-labelled methane, ethane, ethylene, acetylene, propane, propylene and butadiene. The yields of methane and ethylene -f- ethane relative to acetylene, extrapolated to zero dose, where 0.12 0.03 and 0.49 0.00, respectively. Iodine does not affect the purely hot atom reactions producing... 

Synchrotron irradiation of 2-methylpentane produced C-labelled methane, ethane -h ethylene, acetylene, propane + propylene and 1,3-butadiene. The yield ratios of methane and ethane -t- ethylene to acetylene were 0.16 + 0.01 and 0.40 + 0.04, respectively, while the yield ratios for propane + propylene and butane were 0.097 + 0.015 and 0.15 0.02, respectively. 

The method involves the irradiation of a sample with polychromatic X-rays (synchrotron radiation) which inter alia promote electrons from the innermost Is level of the sulfur atom to the lowest unoccupied molecular orbitals. In the present case these are the S-S antibonding ct -MOs. The intensity of the absorption lines resulting from these electronic excitations are proportional to the number of such bonds in the molecule. Therefore, the spectra of sulfur compounds show significant differences in the positions and/or the relative intensities of the absorption lines [215, 220, 221]. In principle, solid, liquid and gaseous samples can be measured. 

A XAS experiment involves the irradiation of a sample with a tuneable source of monochromatic X-rays, usually from a synchrotron facility (high brilliance). Third-generation synchrotrons have sufficient intensity to observe XAFS spectra up to 100 keV. Nevertheless, laboratory-scale XAFS spectroscopy is of importance, despite the vast availability of synchrotron beam time [305]. 

The question also arises as to where the chiral molecules came from. Were the L-amino acids or the D-sugars selected on the primeval Earth, or are exuaterresuial sources responsible for the homochirality This second possibility is dealt with by hypotheses on the effect of circularly polarised light, of extraterrestrial origin, on chiral molecules in the molecular clouds from which the solar system was formed. One such hypothesis was proposed by Rubenstein et al. (1983) and developed further by others, particularly A. W. Bonner (Bonner and Rubenstein, 1987) both scientists worked at Stanford University. The authors believe that the actual radiation source was synchrotron radiation from supernovae. The excess of one enantiomeric form generated by this irradiation process would have needed to be transported to Earth by comets and meteorites, probably during the bombardment phase around 4.2-3.8 billion years ago. 

Some experiments are aiming at the study of structure evolution. In general, the studied material is isotropic or exhibits simple anisotropy (e.g., fiber symmetry). Most frequently the material is irradiated in normal-transmission geometry. A synchrotron beamline is necessary, because in situ recording during the materials processing is requested with a cycle time of seconds between successive snapshots (time-resolved measurements). 

A variety of alternating copolymers based on H-allyl- and N-(3-ethynylphenyl)maleimides, with substituted styrenes and vinyl ethers, have been prepared and their response to x-ray irradiation studied. Broadband and monochromatic x-ray exposures were conducted at the Stanford Synchrotron Radiation Laboratory. Sensitivities were observed to correlate with mass absorption coefficients of the copolymers and were found to be as high as 5-10 mJ/cm2. Preliminary fine line lithographic studies indicate 0.5 ion resolution capabilities. 

Fast reactions between pure metal powders (A1 + Ni, A1 + Ti and A1 + Ni + Ti) have been studied by Javel etal. (1997) by using time-resolved X-ray diffraction with the help of synchrotron radiation. The sample (20 X 10 X 2 to 3 mm3 was prepared under purified argon by cold pressing the metal powders mixed in the required proportion. It was then placed in a reaction chamber kept under He gas. A mylar window allows the incident and diffracted X-ray beams to pass in and out. Two small heating devices (tungsten coils on alumina supports) were included. The first one was used to keep the sample at a uniform temperature before ignition and the second one to start the self-propagating reaction at one end of the sample. X-rays irradiated the centre of the specimen. 

Watanabe, R. Usami, N. Kobayashi, K. Oxidation yield of the ferrous ion in a Fricke solution irradiated with monochromatic synchrotron soft X-rays in the 1.8-10 keV region. Int. J. Radiat. Biol. 1995, 68 (2), 113-120. 

A Laue X-ray diffraction pattern from a protein crystal. A stationary crystal is irradiated with very intense white, multiwavelength X rays from a synchrotron source. The diffraction pattern is rich in information. A single 0.1 ms X-ray pulse may provide a pattern with enough information to determine a three-dimensional structure. 

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