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排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
G. Mante R. Claessen T. Buslaps S. Harm R. Manzke M. Skibowski J. Fink 《Zeitschrift für Physik B Condensed Matter》1990,80(2):181-185
Applying angle-resolved photoemission spectroscopy of high angular and energy resolution we have measured the electronic structure of single crystals of Bi2Sr2CaCu2O8 near the Fermi energy. Along the high symmetry direction X a band is observed to disperse upwards and to cross the Fermi level, whose unoccupied part constitutes the hole-like carriers responsible for the superconductivity. From spectra along the M direction we find evidence for an electron pocket around the M point. The measured band widths appear to be drastically reduced compared with band structure calculations indicating strong electronic correlation effects. From the observation of Fermi-Dirac-like cut-offs in the spectra due to band crossings through the Fermi level we can confirm the existence and, in particular, the shape of the Fermi surface as calculated by band structure calculations. 相似文献
992.
G. Scamarcio L. Tapfer W. König K. Ploog A. Cingolani 《Applied Physics A: Materials Science & Processing》1990,51(3):252-254
Far infrared reflectivity measurements are performed on a series of GaAs/AlAs multiple quantum well (MQW) heterostructures with systematically varied thicknesses of the constituent layers. In addition to the artificial anisotropy we observe two distinct bulk-like Reststrahlen regions. The widths of the GaAs-like and the AlAs-like Reststrahlen bands strongly depend on the relative thicknesses of the constituent layers of the MQW heterostructures, in excellent agreement with the predictions of the effective-medium theory.Prof. Aldo Cingolani passed away just before the publication of this article. We would like to dedicate this paper to his memory 相似文献
993.
It is shown that laser evaporation of a solid target followed by adiabatic expansion can be used to produce cold beams of neutral small open shell molecules. LIF is applied to detect CuH (X
1), CH (X
2), SiH (X
2), CuO (X
2), and FeO (X
5). A production of 109±1 molecules/sr in a single pulse is obtained for SiH. For a copper target, the optical emission of the jet plume is discussed. 相似文献
994.
995.
G. Eyink 《Communications in Mathematical Physics》1989,126(1):85-101
Continuing the analysis of a previous paper, the present work applies rigorous renormalization group methods to the hierarchical models to establish the existence of field theories with non-Gaussian ultraviolet renormalization group fixed points in 4- dimensions. 相似文献
996.
In view of physical applications (especially to QCD Sum Rules), the following problem, pertaining to analytic extrapolation techniques, is studied. We are considering amplitudes, which are (real) analytic functions in the complex plane cut along=[s
0, ). A modelF
0(s) of the amplitude is given through the values ofF
0(s) on some interval=[s
2,s
1] (withs
1<s
0) and the values of its discontinuity on. These values are approximate, and are supplemented by prescribed error channels, measured inL
-norm (both on and). Investigating the compatibility between these data leads to an extremum problem which is solved up to a point where numerical methods can be implemented.Unité Associée au CNRS no040768 相似文献
997.
G. Pirillo 《Archiv der Mathematik》1989,53(1):1-3
Ohne Zusammenfassung 相似文献
998.
G. P. Jones B. A. Cornell E. Horn E. R. T. Tiekink 《Journal of chemical crystallography》1989,19(4):715-723
The crystal structures of dimethylsuccinate (DMS) and dimethyloxalate (DMO) have been determined to facilitate the determination of the C-13 chemical shielding tensors of the carbonyl carbon in esters. Crystals of DMS are monoclinic, space groupC2/c,Z=4,a=13.154(4),b=6.156(1),c=9.363(4)Å,=98.53(3)°. The structure was solved by direct methods and refined by leastsquares procedures to giveR=0.071 for 932 observed data. Crystals of DMO are monoclinic space group,P21/n,Z=2, witha=3.891(1),b=11.879(2),c=6.213(2) Å,=103.32(2)°. The structure is the same (within experimental error) as that reported by Dougill and Jeffrey (1953) and refined to giveR=0.074 for 395 observed data. 相似文献
999.
Hearing talkers produce shorter vowel and word durations in multisyllabic contexts than in monosyllabic contexts. This investigation determined whether a similar effect occurs for deaf talkers, a population often characterized as lacking coarticulation in their speech. Four prelingually deafened adults and two hearing controls produced three sets of word sequences. Each set included a kernel word and six derived forms (e.g., "speed," "speedy," "speeding," etc.). The derived forms were created by adding unstressed and stressed syllables to the kernel form. A spectrographic analysis indicated that the deaf subjects did not always decrease word and vowel durations for the derivatives. Unlike hearing speakers, they often did not reduce vowel segments more than consonant segments. Three explanations are forwarded for the shortening effects. One relates to the implementation of temporal rules, the second concerns the organization imposed upon the articulators to produce speech, and the third suggests a language-independent vocal tract characteristic. The role of auditory information in developing the shortening effects is also considered. 相似文献
1000.
G. D. Raikov 《Communications in Mathematical Physics》1989,124(4):665-685
We consider the discrete spectrum of the selfadjoint Schrödinger operatorA
h
=–h
2
+V defined inL
2(m) with potentialV which steadies at infinity, i.e.V(x)=g+|x|–
f(1+o(1)) as |x| for>0 and some homogeneous functionsg andf of order zero. Let
h
(),0, be the total multiplicity of the eigenvalues ofA
h
smaller thanM–, M being the minimum value ofg over the unit sphereS
m–1 (hence,M coincides with the lower bound of the essential spectrum ofA
h
). We study the asymptotic behaviour of
1() as0, or of
h
() ash0, the number0 being fixed. We find that these asymptotics depend essentially on the structure of the submanifold ofS
m–1, where the functiong takes the valueM, and generically are nonclassical, i.e. even as a first approximation (2)
m
h
() differs from the volume of the set {(x, )2m:h
2||2+V(x)<M–}.Partially supported by Contract No. 52 with the Ministry of Culture, Science and Education 相似文献