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991.
LIN ChihKai MINEO Hirobumi CHAO ShengDer FUJIMURA Yuichi HAYASHI Michitoshi LIN ShengHsien 《中国科学:化学(英文版)》2012,55(4):578-592
When femto-second (fs) time-resolved experiments are used to study ultrafast processes, quantum beat phenomena are often observed. In this paper, to analyze the fs time-resolved spectra, we will present the density matrix method, a powerful theoretical technique, which describes the dynamics of population and coherence of the system. How to employ it to study the pump-probe experiments and fs ultrafast processes is described. The ππ*→nπ* transition of pyrazine is used as an example to demonstrate the application of the density matrix method. Recently, Suzuki’s group have employed the 22 fs time resolution laser to study the dynamics of the ππ* state of pyrazine. In this case, conical intersection is commonly believed to play an important role in this non-adiabatic process. How to treat the effect of conical intersection on non-adiabatic processes and fs time-resolved spectra is presented. Another important ultrafast process, vibrational relaxation, which takes place in sub-ps and ps range and has never been carefully studied, is treated in this paper. The vibrational relaxation in water dimer is chosen to demonstrate the calculation. It should be noted that the vibrational relaxation of (H2O)2 has not been experimentally studied but it can be accomplished by the pump-probe experiments. 相似文献
992.
Ordered nanofacet structures on vicinal 6H-SiC(0 0 0 1) surfaces, consisting of pairs of a (0 0 0 1) basal plane and a facet, are investigated in terms of stable surface stacking of the (0 0 0 1) basal planes. The surface termination of S3 (or S3*), i.e., ABC (or A*C*B*), was suggested by a structural model based on quantized step-bunching, which typically gives a one-unit-cell bunched step configuration at the facet. Here, we evaluate the surface termination at basal planes covered with a layer of silicon oxynitride by means of quantitative low-energy electron diffraction (LEED) analysis combined with scanning tunneling microscopy (STM), and show the validity of the structural model proposed. 相似文献
993.
Koichiro Hayashi 《Journal of magnetism and magnetic materials》2009,321(5):450-457
Fe3O4 nanoparticle/organic hybrids were synthesized via hydrolysis using iron (III) acetylacetonate at ∼80 °C. The synthesis of Fe3O4 was confirmed by X-ray diffraction, selected-area diffraction, and X-ray photoelectron spectroscopy. Fe3O4 nanoparticles in the organic matrix had diameters ranging from 7 to 13 nm depending on the conditions of hydrolysis. The saturation magnetization of the hybrid increased with an increase in the particle size. When the hybrid contained Fe3O4 particles with a size of less than 10 nm, it exhibited superparamagnetic behavior. The blocking temperature of the hybrid containing Fe3O4 particles with a size of 7.3 nm was 200 K, and it increased to 310 K as the particle size increased to 9.1 nm. A hybrid containing Fe3O4 particles of size greater than 10 nm was ferrimagnetic, and underwent Verwey transition at 130 K. Under a magnetic field, a suspension of the hybrid in silicone oil revealed the magnetorheological effect. The yield stress of the fluid was dependent on the saturation magnetization of Fe3O4 nanoparticles in the hybrid, the strength of the magnetic field, and the amount of the hybrid. 相似文献
994.
A. Ya. Faenov T. A. Pikuz Y. Fukuda M. Kando H. Kotaki T. Homma K. Kawase T. Kameshima A. Pirozhkov A. Yogo M. Tampo M. Mori H. Sakaki I. Hayashi T. Nakamura S. A. Pikuz Jr. V. Kartashev I. Yu. Skobelev A. Giulietti C. A. Checchetti A. S. Boldarev V. A. Gasilov A. I. Magunov S. Kar M. Borghesi P. Bolton H. Daido T. Tajima I. Kato S. V. Bulanov 《JETP Letters》2009,89(10):485-491
It has been shown that a femtosecond plasma of cluster targets is an almost isotropic source of fast ions and, hence, can be used to obtain ionographic images with a wide field of view. The spatial resolution of the resulting ionographic images is no worse than 600 nm, which corresponds to a uniquely high value of about 105 of the ratio of the field of view to the resolution. The use of 100–300-keV ion fluxes ensures the sensitivity of the method to the sample thickness of no worse than 100 nm even for samples consisting of light chemical elements (C, H). The proposed method can be used to obtain images of low-contrast biological objects, thin films, membranes, and other nanostructured objects. 相似文献
995.
H. Nakamura N. Hayashi N. Nakai M. Okumura M. Machida 《Physica C: Superconductivity and its Applications》2009,469(15-20):908-911
In order to resolve a discrepancy of the magnetic moment on Fe between the experimental and calculation results, we perform first-principle electronic structure calculations for iron-based superconductors LaFeAsO1-xFx in which x=0.0 and x=0.125 by using the LSDA + U framework. Consequently, we confirm in both the mother and doped compounds that negative U correction is crucial in matching the calculated magnetic moment with the observed one. A reason of the negative correction is that the Coulomb interaction on Fe orbitals is unexpectedly screened than LSDA’s expectation. We discuss which type of situation emerges when the negative U is a good correction in these compounds. 相似文献
996.
997.
Two new Lycopodium alkaloids, lycopladines F (1) and G (2), have been isolated from the club moss Lycopodium complanatum, and the structures and relative stereochemistries of 1 and 2 were elucidated on the basis of spectroscopic data. Lycopladine F (1) is a rare C16N2-type Lycopodium alkaloid possessing an amino acid residue (C4N). 相似文献
998.
Molecular dynamics (MD) simulations of cellulose IIII crystal models have been carried out. The crystal models were composed by either 24 or 48 cellooligomers consisting of either
20 or 40 residues and were surrounded by waters in a periodic boundary box. Two base plane types differing in a constituent
crystal lattice plane, (0 −1 0) × (0 1 0) and (1 0 0) × (0 1 0), were additionally considered. Among the resulting eight crystal
models, an overall structure conversion was observed for the seven models. The final structures had a triclinic-like chain
arrangement involving one-quarter staggering chains with respect to its axis. The successive, local transformation involving
cooperative bends in cellooligomers was observed during the structure conversion. Only the 48 × 20-mer model having the (0 −1 0)
lattice plane retained the original crystal structure throughout a 2.5-ns simulation. The MD simulations with an implicit
solvent system and a vacuum system were also performed to asses a solvent effect on the structure conversion. 相似文献
999.
This paper studies Nash implementation in the job-matching market where each worker works for only one firm and a firm hires
as many workers as it wishes. We show that the competitive equilibrium correspondence (CEC) is the smallest Nash implementable
correspondence satisfying individual rationality and Pareto indifference. Furthermore, the CEC is the minimal monotonic extension of the worker-optimal and firm-optimal subcorrespondences. We offer
two “good” mechanisms that implement this correspondence in Nash equilibrium. 相似文献
1000.
Daisuke Sukeguchi Shuichi Nakamura Yasuhiko Hayashi Tetsuo Soga 《Journal of fluorine chemistry》2009,130(3):361-5525
Synthesis and spectroscopic investigation of trifluoroethoxy-coated phthalocyanine-fullerene dyad 2 has been described. While nonfluorinated phthalocyanine-fullerene dyad 1 showed an efficient property of intramolecular photoinduced electron transfer, dyad 2, regardless of its covalently linked dyad system, appears not to show any electronic communication between fullerene and phthalocyanine. This observation is presumably due to the strong electron withdrawing nature of 12 trifluoroethoxy groups; fluorine leads phthalocyanine to become an acceptor whose electronic accepting property is equivalent to that of fullerene. This is a unique example that fluorine can terminate electronic communication in the covalently fullerene-phthalocyanine dyad system. 相似文献