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201.
A. Hamnett S.T. Hood C.E. Brion 《Journal of Electron Spectroscopy and Related Phenomena》1977,11(3):263-274
The binding-energy spectrum of phosphine has been obtained over the range 0–30 eV using the binary (e, 2e) coincidence method. The momentum distribut 相似文献
202.
B. S. Kirkiacharian M. Gomis H. G. Tongo J. Mahuteau J. D. Brion 《Magnetic resonance in chemistry : MRC》1984,22(2):106-108
The study of a set of 3-benzylidene-4-chromanones, 3-benzyl-4-chromanones, 3-benzyl-3-hydroxy-4-chromanones and 3-benzylchromones (homoisoflavonoids) by 13C NMR spectroscopy shows the influence of the structure of these molecules on the chemical shifts of the more characteristic carbon atoms at positions 2, 3 and 4. 相似文献
203.
204.
[STRUCTURE: SEE TEXT] The first platinum-catalyzed selective silylation of aryl halides including aryl iodides and bromides having an electron-withdrawing group is described. The reaction takes place rapidly in NMP with triethylsilane as a silicon source and sodium acetate to provide functionalized aryltriethylsilanes in moderate to good yields. Heteroaromatic halides also were found to be readily silylated with triethylsilane. The procedure is chemoselective and tolerates a wide variety of functional groups. 相似文献
205.
El Dib G Chakir A Roth E Brion J Daumont D 《The journal of physical chemistry. A》2006,110(25):7848-7857
The ultraviolet absorption spectrum of benzylperoxy radical and the kinetics of the reactions 2C(6)H(5)CH(2)O(2) --> products (I) and C(6)H(5)CH(2)O(2) + HO(2) --> products (II) are studied. Experiments are carried out using the laser photolysis technique with time-resolved UV-visible absorption spectroscopy over the temperature range 298-353 K and the pressure range 50-200 Torr. The UV spectrum is determined relative to the known cross section of the ethylperoxy radical C(2)H(5)O(2) at 250 nm. Using factor analysis, the spectrum obtained is refined and the concentrations of the main absorbing species are extracted. The kinetic parameters are determined by analyzing and simulating the temporal profiles of the species concentrations and the experimental optical densities in the spectral region 220-280 nm. These are obtained using the recent UV spectra of the absorbing species existing in our mechanism. The Arrhenius expressions for reactions I and II are (cm(3).molecule(-1).s(-1)) k(I) = 2.50 x 10(-14)e(1562/)(T) and k(II) = 5.70 x 10(-14)e(1649/)(T). Our results are discussed and compared to literature data. 相似文献
206.
In the manganites L1?xMxMnO3 (L = La, Nd, Pr, …; M = Sr, Ba, Ca, …), the doping concentration introduces a mixed valence (Mn3+, Mn4+) which governs the magnetic and electric properties of the compound. Mn3+ (S = 2) is scarcely observed in electron spin resonance (ESR). In contrast, Mn4+ (S = 3/2), is a good ESR probe. However, X-band measurements show an enhanced Mn4+ susceptibility, which is the signature of some kind of coupling of the Mn4+ ions with the Mn3+ ions, but its exact nature is still controversial. We present multifrequency ESR experiments (9–385 GHz) obtained on different systems (La1?δMnO3, La1?xMnO3, La1?xCaxMnO3, and Nd1?xCaxMnO3) in the low-concentration range (0 <x< 0.33). In the paramagnetic regime, the Mn3+ spectrum cannot be observed because of fast relaxation. The signal arises from polarons, whose size, temperature and magnetic field dependences vary with M andx. The single line observed in the metallic compound evolves towards a double-peak structure visible at high frequency in La0.97MnO3. Its evolution with temperature below the magnetic transition reveals the presence of manganese ions in a different magnetic environment, i.e., phase separation. The magnetic order of the separated phase is not ferromagnetic. It is a more complex order, which depends substantially on the nature of the cation M. 相似文献
207.
208.
A. Grüger P. Gotthardt M. Pnitsch H. G. Brion R. Kirchheim 《Journal of Polymer Science.Polymer Physics》1998,36(3):483-494
Pressure-composition isotherms were determined at 20°C for CO2 in Kapton and various substituted polycarbonates and for H2O, Ar, N2, CH4, and acetone in bisphenol-A-polycarbonate. The isotherms are described by two parameters an average free energy of sorption and a width of a Gaussian distribution of free sorption energies. Within the framework of a recent model these parameters can be calculated assuming an elastic distortion of the polymer caused by the incorporation of solute atoms in preexisting holes. By comparing experimental values with predictions of the model the experimental width of the free energy distribution is only 30% smaller than the theoretical one. Functional relationships are obeyed between the sorption parameters on the one hand and glass transition temperature, average hole volume, and molecular volume of the solute on the other hand. Deviations occur for larger molecules like acetone and ethylene which are attributed to a viscoelastic distortion of the polymer. Comparing free energies of solution for the rubbery and glassy state of the polymer reveals more negative values for the glassy polymers despite their extra elastic distortion energy. This discrepancy is overcome by taking into account that the occupied volume has to be re-formed in the case of the rubbery or liquid polymer. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 483–494, 1998 相似文献