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641.
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643.
V. Karpus A. Suchodolskis U.O. Karlsson L. Giovanelli S. Brühne 《Applied Surface Science》2006,252(15):5411-5414
We present a detailed analysis of the Mg 2p shallow core-levels measured on icosahedral single-grain ZnMgY, ZnMgHo, and ZnMgEr quasicrystals during a photoelectron microscopy study. The synchrotron radiation photoemission measurements were performed on in situ cleaved samples at a pressure of 10−10 mbar and at low temperature, typically 90-150 K. The Mg 2p photoemission lines are essentially broadened as compared to those of the Mg 2p spin-orbit doublet recorded on the Zn2Mg crystalline Laves phase. The broadening is associated to the coordination shifts of the Mg 2p level due to the inequivalent magnesium sites in the quasicrystalline lattice. The coordination shifts are calculated on the basis of i-ZnMg(Ho, Y) atomic structure data, recently determined from the pair distribution function analysis. The coordination shifts obtained are up to 0.2 eV. The Mg 2p experimental spectral intensity is nicely reproduced by a superposition of coordination-shifted Mg 2p spin-orbit doublets. 相似文献
644.
Near-infrared laser photoacoustic detection of methane: the impact of molecular relaxation 总被引:1,自引:0,他引:1
A photoacoustic sensor has been developed for trace-gas monitoring using a near-infrared semiconductor laser emitting in the
2ν3 band of methane at 1.65 μm. The apparatus was designed for on-line process control in the manufacturing of the novel low-water-peak
fibres developed for optical telecommunications. The importance of collisional relaxation processes in the generation of the
photoacoustic signal is reported in the particular case of CH4 detection in dry O2 and O2–N2 mixtures. The negative influence of these effects results in a strongly reduced and phase-shifted photoacoustic signal, induced
by a fast resonant coupling between the vibrational states of methane and oxygen, associated with the slow relaxation of the
excited oxygen molecules. An unusual parabolic response of the sensor with respect to the methane concentration has been observed
and is discussed. Finally, the beneficial effect of several species, including water vapour and helium, acting as a catalyst
to hasten the relaxation of the CH4–O2 system, is demonstrated.
PACS 42.62.Fi; 33.20.Ea; 34.50.Ez 相似文献
645.
The renormalization of the dispersion law for two-dimensional excitons in a magnetic field is studied by the Green's-function method taking into account multiphonon processes.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 3–7, April, 1987. 相似文献
646.
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648.
The first twelve members of the n-alkyl 2,5-bis-(4'-cyanobiphenyloxybutyloxy)-benozates have been prepared. The compounds are nematogenic; in addition the first three members exhibit a smectic A phase. The nematic-isotropic transition temperatures decrease with little or no alternation on increasing the number of methylene groups in the lateral chain; this is analogous to the behaviour found in monomeric and polymeric mesogens possessing lateral alkyl chains. 相似文献
649.
D. W. Taylor V. Villas-Boas Q. Lu M. F. Rossignol F. P. Missell D. Givord S. Hirosawa 《Journal of magnetism and magnetic materials》1994,130(1-3):225-236
We studied the coercivity in magnets of composition R17Fe83−χBχ (R = Nd, Pr and χ = 8, 30), using measurements of the coercive field Hc, its angular dependence, and the magnetic viscosity coefficient Sv, for temperatures between 4.2 and 500 K. The results are discussed in relation to a model which does not specifically consider the detailed mechanisms involved in magnetization reversal, but which provides information about the magnetic properties in the activation volume v where magnetization reversal is initiated. It is concluded that the ordering temperature in v tends to be slightly smaller than in the bulk and that the room temperature anisotropy in v is not strongly reduced with respect to the bulk value. Finally, a direct evaluation of the dipolar interactions is in good agreement with results obtained from Hc(T). 相似文献
650.
S. Yu. Kun V. Yu. Denisov A. V. Vagov 《Zeitschrift für Physik A Hadrons and Nuclei》1997,359(3):257-262
We employ the statistical reactions with memory approach to study oscillating excitation functions in the 28 Si(E lab = 120–126.75 MeV)+64 Ni strongly dissipative reaction and the time evolution of the collision process. The nonself-averaging of the oscillations in the excitation functions is interpreted as indication of quantum chaos and damping of the coherent nuclear rotation in dissipative heavy-ion collisions. 相似文献