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排序方式: 共有259条查询结果,搜索用时 31 毫秒
31.
Anthony JM Garrett 《Contemporary Physics》2013,54(2):163-165
The dynamic electronic structure of atoms and molecules can be directly observed by means of the (e, 2e) reaction, which measures the distribution of energies and momenta of two electrons in coincidence after a knockout reaction initiated by an electron beam of known momentum incident on a molecular gas target. The molecular state for each event is identified by the electron separation energy. The recoil momentum for each event is known from the difference of measured initial and final momenta. It has been verified that values of this momentum are equal under suitable conditions to the momentum of the electron in the target immediately before knockout. Thus the spherically-averaged electron momentum distribution for each molecular orbital is measured. This is directly related to molecular orbitals calculated by the methods of quantum chemistry. Properties obtained by this method for different types of molecules are discussed. 相似文献
32.
G. Méjean J. Kasparian J. Yu S. Frey E. Salmon R. Ackermann J.P. Wolf L. Bergé S. Skupin 《Applied physics. B, Lasers and optics》2006,82(3):341-345
We report new experimental and numerical results on supercontinuum generation at ultraviolet/visible wavelengths produced
by the propagation of infrared femtosecond laser pulses in air. Spectral broadening is shown to similarly affect single filaments
over laboratory distance scales, as well as broad beams over long-range propagation distances. Numerical simulations display
evidence of the crucial role of third harmonic generation in the build-up of UV–visible wavelengths, by comparison with current
single-envelope models including chromatic dispersion and self-steepening.
PACS 52.38.Hb; 42.65.Tg; 42.65.Jx; 42.68.Ay 相似文献
33.
A range is defined for the effects of parity dependence in heavy-ion scattering. This range is shown to be related to the terms of the antisymmetrizer which exchange the largest number of nucleons between both nuclei. A simple formula, derived in the two-center harmonic oscillator model, gives an upper bound for the parity range. A criterion is proposed to determine whether a parity-dependent real part should be used in heavy-ion optical potentials. The most important parity effects should be expected in scattering between nuclei with neighbouring masses. 相似文献
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The first part of this paper deals with the Frey-Salmon irreversibility hypothesis, the kinetic equation that is deduced therefrom, and the comparison with experiment for the viscosity and thermal conductivity coefficients. The relaxation time which has been introduced is the average value of the duration of a collision. The second part deals with a new irreversibility hypothesis which leads to a kinetic equation of the same form as the first but in which the relaxation time is deduced from the interparticle potential. 相似文献
37.
Paolo Salmon 《Milan Journal of Mathematics》1980,50(1):135-140
38.
Salmon L Thuéry P Asfari Z Ephritikhine M 《Dalton transactions (Cambridge, England : 2003)》2006,(24):3006-3014
Reactions of UCl4 with 25,27-dimethoxy-5,11,17,23-tetra-tert-butylcalix[4]arene (H2Me2calix) in THF or pyridine at 80 degrees C gave [UCl2(Me2calix)L2] [L = THF (1) or pyridine (2)]. Similar treatment of U(acac)(4) (acac = MeCOCHCOMe) with H2Me2calix in THF or pyridine afforded [U(acac)2(Me2calix)] (3). The bis-calixarene compound [U(Me2calix)(H2calix)] (4) was obtained by reaction of U(OTf)4 or U(OTf)3 with H2Me2calix in pyridine at 110 degrees C. Treatment of UCl4 with H2Me2calix in pyridine at 110 degrees C gave [Mepy][UCl2(Hcalix)(py)2] (5) resulting from demethylation and acid cleavage of the methoxy groups of the calixarene ligand of 2. Adventitious traces of air were responsible for the formation of [Hpy][Mepy]4[{UCl(calix)}3(mu3-O)][UCl6] (6) during the reaction of UCl4 and H2Me2calix, and of [{U(Me2calix)(mu3-O)LiCl(THF)}2] (7) during the reaction of 2 with tBuLi. The X-ray crystal structures of 1.2THF, 2.2py, 3.0.25L (L = THF and py), 4.2py, 5, 6.3py and 7.THF have been determined. 相似文献
39.
The relation between the fragility of glass-forming systems, a parameter which describes many of their key physical characteristics, and atomic scale structure is investigated by using neutron diffraction to measure the topological and chemical ordering for germania, or GeO(2), which is an archetypal strong glass former. We find that the ordering for this and other tetrahedral network-forming glasses at distances greater than the nearest neighbor can be rationalized in terms of an interplay between the relative importance of two length scales. One of these is associated with an intermediate range, the other with an extended range and, with increasing glass fragility, it is the extended range ordering which dominates. 相似文献
40.
Cletus A D'Souza Vikramjit Chopra Richard Varhol Yuan-Yun Xie Slavita Bohacec Yongjun Zhao Lisa LC Lee Mikhail Bilenky Elodie Portales-Casamar An He Wyeth W Wasserman Daniel Goldowitz Marco A Marra Robert A Holt Elizabeth M Simpson Steven JM Jones 《BMC neuroscience》2008,9(1):1-14