共查询到20条相似文献,搜索用时 31 毫秒
1.
R. Thissen P. Lablanquie R.I. Hall M. Ukai K. Ito 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,4(3):335-342
Photoionization of rare gas clusters in the innervalence shell region has been investigated using threshold photoelectron
and photoion spectrometers and synchrotron radiation. Two classes of states are found to play an important role: (A) valence
states, correlated to dissociation limits involving an ion with a hole in its innervalence ns shell, (B) Rydberg states correlated to dissociation limits involving an ion with a hole in its outervalence np shell plus an excited neutral atom. In dimers, class A states are “bright”, that is, accessible by photoionization, and serve
as an entrance step to form the class B “dark” states; this character fades as the size of the cluster increases. In the dimer,
the “Mulliken” valence state is found to present a shallow potential well housing a few vibrational levels; it is predissociated by the
class B Rydberg states. During the predissociation a remarkable energy transfer process is observed from the excited ion that
loses its innershell electron to its neutral partner.
Received: 10 February 1998 / Revised: 17 July 1998 / Accepted: 31 July 1998 相似文献
2.
G. Labeyrie A. Browaeys W. Rooijakkers D. Voelker J. Grosperrin B. Wanner C.I. Westbrook A. Aspect 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,7(3):341-350
We have constructed a magneto-optical funnel for He atoms and studied its properties using a laser cooled, highly mono-energetic
atomic beam. A simple model of its action allows us to quantitatively understand the observed spot size and “focal length”.
We show that for a fast beam, the velocity damping coefficient plays an important role in determining the focal length of
the device. The observed spot size is limited mainly by transverse heating processes which impose a transverse velocity spread.
The device also permits easy scanning of the focussed spot.
Received 30 October 1998 and Received in final form 27 January 1999 相似文献
3.
N. Petit F. Gervais P. Buvat P. Hourquebie P. Topart 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,12(3):367-372
The reflectivity spectrum of a polyaniline CSA-doped in presence of m-cresol has been measured over the wide wavenumber range
of 15- 9 000 cm
-1 (0.002-1.1 eV) at room temperature. Experimental data compare well with similar experiments performed by another group. The
conductivity spectrum of this conducting polymer has been deduced from the reflectivity spectrum by means of two methods,
Kramers-Kronig transformation and best fit of an “extended Drude” model to the reflectivity spectrum. Whereas the deviation
from Drude behavior was interpreted in terms of Anderson localization or by inhomogeneous disorder by other groups, it is
shown here that a different model developed for conducting oxides that also exhibit non-Drude behavior, applies very well
to this example of conducting polymer.
Received 11 February 1999 and Received in final form 26 April 1999 相似文献
4.
On the properties of small-world network models 总被引:7,自引:0,他引:7
A. Barrat M. Weigt 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(3):547-560
We study the small-world networks recently introduced by Watts and Strogatz [Nature 393, 440 (1998)], using analytical as well as numerical tools. We characterize the geometrical properties resulting from the
coexistence of a local structure and random long-range connections, and we examine their evolution with size and disorder
strength. We show that any finite value of the disorder is able to trigger a “small-world” behaviour as soon as the initial
lattice is big enough, and study the crossover between a regular lattice and a “small-world” one. These results are corroborated
by the investigation of an Ising model defined on the network, showing for every finite disorder fraction a crossover from
a high-temperature region dominated by the underlying one-dimensional structure to a mean-field like low-temperature region.
In particular there exists a finite-temperature ferromagnetic phase transition as soon as the disorder strength is finite.
[0.5cm]
Received 29 March 1999 and Received in final form 21 May 1999 相似文献
5.
V.Yu. Irkhin A.V. Zarubin 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,16(3):463-468
The Kondo divergences owing to interaction of current carriers with local moments in highly correlated electron systems are
considered within the Hubbard and s-d exchange models with infinitely strong on-site interaction, the many-electron Hubbard representation being used. The picture
of density of states containing a peak at the Fermi level is obtained. Various forms of the self-consistent approximation
are used. The problem of the violation of analytical properties of the Green's function is discussed. Smearing of the “Kondo”
peak owing to spin dynamics and finite temperatures is investigated.
Received 25 November 1999 and Received in final form 31 January 2000 相似文献
6.
X. Chen 《Applied Physics A: Materials Science & Processing》1999,69(4):453-455
We have observed a new polarisation pattern in terbium gallium garnet which is both laser excited and mechanically stressed.
The pattern can be characterized by a splitting from a “one dot” structure to a “two dots” structure. We have found that the
new pattern is very sensitive to the orientation and the strength of the external forces applied to the sample. Thanks to
this sensitivity and to the image simplicity, this new effect may be used in a vectorial force sensor and actuator.
Received: 25 March 1999 / Accepted: 20 April 1999 / Published online: 25 August 1999 相似文献
7.
P. Schwab 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(2):189-192
In a weakly disordered metal electron interactions are responsible for both decoherence of the quasi-particles as well as
for quantum corrections to thermodynamic properties. We consider electrons which are interacting with two-level-systems. We
show that the two-level-systems enhance the average equilibrium (“persistent”) current in an ensemble of mesoscopic rings.
The result supports the recent suggestion that two puzzles in mesoscopic physics may be related: The low temperature saturation
of the dephasing time and the high persistent current in rings.
Received 26 May 2000 相似文献
8.
M. Geoghegan F. Boué G. Bacri A. Menelle D.G. Bucknall 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,3(1):83-96
We have used neutron reflectometry to measure interfacial widths between two polystyrene films, where either one or both films
are crosslinked. The observed interfacial width between two networks is larger than the size expected for “dangling ends”,
which suggests motion of heterogeneous regions of the networks. In the case when one of the networks is replaced by a linear
polymer, the interfacial profile can be asymmetric with a diffusion “front” of linear polymer penetrating the network to a
length scale of up to 200 ?. In the case of a more densely crosslinked network and a high molecular weight linear polymer
the interface is symmetric implying negligible penetration.
Received: 4 December 1996 / Revised: 13 October 1997 / Accepted: 23 December 1997 相似文献
9.
X.H. Yan J.W. Ding Q.B. Yang 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,20(2):157-163
Developing a renormalization group approach, we study the hopping conductivity of nanocrystalline chains with different site
energies. Exact calculations show that many parameters including nano-sizes, randomness of grain distributions, lattice distortions,
site energies, transition rates, Fermi energy, and temperature influence the conductivity. Some new singular features, for
example the frequency shift, the amplitude fluctuations, and the interchange between “peak” and “valley” behavior of the imaginary
part of the conductivity can be caused by certain parameters mentioned above, while the interface distortions modulate mainly
the overall amplitudes of the conductivity at the whole frequency region.
Received 13 January 2000 and Received in final form 12 September 2000 相似文献
10.
D.V. Kosachiov E.A. Korsunsky 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,11(3):457-463
Frequency conversion process is studied in a medium of atoms with a configuration of levels, where transition between two lower states is driven by a microwave field. In this system, conversion
efficiency can be very high by virtue of the effect of electromagnetically induced transparency (EIT). Depending on intensity
of the microwave field, two regimes of EIT are realized: “dark-state” EIT for the weak field, and Autler-Townes-type EIT for
the strong one. We study both cases via analytical and numerical solution and find optimum conditions for the conversion.
Received 13 December 1999 and Received in final form 6 March 2000 相似文献
11.
N. Andrenacci P. Pieri G.C. Strinati 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(4):637-642
We consider a system of fermions in the continuum case at zero temperature, in the strong-coupling limit of a short-range
attraction when composite bosons form as bound-fermion pairs. We examine the density dependence of the size of the composite
bosons at leading order in the density (“dilute limit”), and show on general physical grounds that this size should decrease with increasing density, both in three and two dimensions. We then compare with the analytic zero-temperature mean-field
solution, which indeed exhibits the size shrinking of the composite bosons both in three and two dimensions. We argue, nonetheless,
that the two-dimensional mean-field solution is not consistent with our general result in the “dilute limit”, to the extent
that mean field treats the scattering between composite bosons in the Born approximation which is known to break down at low
energy in two dimensions.
Received 3 June 1999 and Received in final form 29 July 1999 相似文献
12.
F. Volino G. Gebel H. Gérard 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,16(1):25-35
A simple lattice model based on generalised diffusion equations and Gaussian statistics, aimed at describing diffusive translational
and rotational motions, is presented. It is shown that it allows the generation of correlation functions relevant to spectroscopic
techniques that are very similar to those experimentally observed in a large variety of complex systems. For some ranges of
values of the model parameters, these functions, which can be expressed in closed mathematical forms, can be approximately
represented by the sum of two exponentials or by “stretched" exponentials.
Received 17 September 1999 and Received in final form 10 February 2000 相似文献
13.
X. Waintal J.-L. Pichard 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,1(1):117-121
For N interacting particles in a one dimensional random potential, we study the structure of the corresponding network in Hilbert
space. The states without interaction play the role of the “sites”. The hopping terms are induced by the interaction. When
the one body states are localized, we numerically find that the set of directly connected “sites” is multifractal. For the
case of two interacting particles, the fractal dimension associated to the second moment of the hopping term is shown to characterize
the Golden rule decay of the non interacting states and the enhancement factor of the localization length.
Received: 17 April 1998 / Accepted: 14 May 1998 相似文献
14.
R. Bulla M. Potthoff 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(2):257-264
The Mott-Hubbard metal-insulator transition is studied within a simplified version of the Dynamical Mean-Field Theory (DMFT)
in which the coupling between the impurity level and the conduction band is approximated by a single pole at the Fermi energy.
In this approach, the DMFT equations are linearized, and the value for the critical Coulomb repulsion can be calculated analytically. For the symmetric single-band Hubbard model at zero temperature, the critical value is found
to be given by 6 times the square root of the second moment of the free (U=0) density of states. This result is in good agreement with the numerical value obtained from the Projective Selfconsistent
Method and recent Numerical Renormalization Group calculations for the Bethe and the hypercubic lattice in infinite dimensions.
The generalization to more complicated lattices is discussed. The “linearized DMFT” yields plausible results for the complete
geometry dependence of the critical interaction.
Received 6 May 1999 and Received in final form 2 July 1999 相似文献
15.
William Arveson 《Communications in Mathematical Physics》2000,211(1):63-83
A mathematical notion of interaction is introduced for noncommutative dynamical systems, i.e., for one parameter groups of
*-automorphisms of endowed with a certain causal structure. With any interaction there is a well-defined “state of the past” and a well-defined
“state of the future”. We describe the construction of many interactions involving cocycle perturbations of the CAR/CCR flows
and show that they are nontrivial. The proof of nontriviality is based on a new inequality, relating the eigenvalue lists
of the “past” and “future” states to the norm of a linear functional on a certain C
*-algebra.
To the memory of Irving Segal
Received: 12 October 1999 / Accepted: 21 October 1999 相似文献
16.
É. Falcon S. Fauve C. Laroche 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,7(2):183-186
We report experimental results on the behavior of an ensemble of inelastically colliding particles, excited by a vibrated
piston in a vertical cylinder. When the particle number is increased, we observe a transition from a regime where the particles
have erratic motions (“granular gas”) to a collective behavior where all the particles bounce like a nearly solid body. In
the gas-like regime, we measure the density of particles as a function of the altitude and the pressure as a function of the
number N of particles. The atmosphere is found to be exponential far enough from the piston, and the “granular temperature”, T, dependence on the piston velocity, V, is of the form , where is a decreasing function of N. This may explain previous conflicting numerical results.
Received 1 February 1999 相似文献
17.
K. Ivanova 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,15(2):327-330
The two-dimensional Ausloos et al. model of fluid invasion, freezing and thawing in a porous medium is elaborated upon and investigated in order to take into
account the pore volume redistribution and conservation during freezing. The results are qualitatively different from previous
work, since the damaged pore sizes are found to be much less than the possible maximum value and is reached after a large
number of invasion-freezing-thawing cycles, e.g. the material is “slowly damaged”. The pore size distribution is thus found in better agreement with expected practical findings.
The successive invasion percolation clusters are still found to be self-avoiding with aging. The cluster size decreases with
a power law as a function of invasion-frost-thaw iterations. The aging kinetics is also discussed through the normalized totally
invaded pore volume.
Received 24 September 1999 and Received in final form 5 January 2000 相似文献
18.
R. Dimova C. Dietrich A. Hadjiisky K. Danov B. Pouligny 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,12(4):589-598
We study the general problem of the friction felt by a spherical solid particle which moves parallel to the membrane of a
spherical vesicle. Experiments are carried out with SOPC vesicles at room temperature, with different particle and vesicle
sizes. Experimental data show considerable finite-size effects whenever the particle is not very small compared to the vesicle.
These effects are found consistent with the hydrodynamical theory of the vesicle-particle problem. This agreement allows for
a “robust” determination of membrane viscosity, independently of particle and vesicle sizes.
Received 4 January 1999 and Received in final form 11 May 1999 相似文献
19.
E. Rasel F. Pereira Dos Santos F. Saverio Pavone F. Perales C.S. Unnikrishnan M. Leduc 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,7(3):311-316
We report a study of transverse laser cooling on a metastable helium beam using spectrally broadened diode lasers (“white
light") to increase its flux. For this purpose, beam profile and atomic flux versus laser power and other parameters have been characterized. We have performed experiments to compare this technique with other
transverse cooling methods using monochromatic light. Best results are obtained with a “ziz-zag" configuration using “white
light".
Received 21 December 1998 and Received in final form 27 May 1999 相似文献
20.
N. Petit C. Daulan J.-C. Soret A. Maignan F. Gervais 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(4):617-625
The temperature dependence of the reflectivity spectra of three manganites ceramics with compositions Pr0.7Ca0.3MnO3, Pr0.7Ca0.25Sr0.05MnO3 and Pr0.7Ca0.1Sr0.2MnO3 has been investigated by infrared reflectivity spectroscopy in the wave number range 0.005-1.1 eV. The compound Pr0.7Ca0.25Sr0.05MnO3 which shows the largest conductivity jump at the ferromagnetic-paramagnetic phase transition has been studied in details.
The optical conductivity of this compound is deduced from the best fit to reflectivity spectra of a “double-damping Drude”
model, itself derived from the factorized form of the dielectric function. Excellent agreement with Kramers-Kronig transformation
is reported. The model allows in particular to discriminate the contributions to the optical conductivity of trapped charges
(polarons) and mobile charge carriers.
Received 20 July 1999 and Received in final form 15 October 1999 相似文献