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1.
2.
Passive microrheological techniques using particle tracking have been developed for the study of the gelation of hectorite
suspensions. By following the Brownian motion of the particles, it is possible to determine the increasing caging of the particles
with time, as the system gels. Since only the Brownian motion is followed, the gelation process itself should not be affected
by the measurement. As gelation proceeds the increasing heterogeneity of the particle environments can be monitored by a variety
of measures, including kurtosis. An effective viscosity can be extracted from the measurements and used to indicate the gelation
process. 相似文献
3.
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
4.
C. Fort A. Bambini L. Cacciapuoti F.S. Cataliotti M. Prevedelli G.M. Tino M. Inguscio 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,3(2):113-118
We report on a theoretical and experimental investigation of 39K magneto-optical trapping. The small hyperfine splitting characterizing the upper level of the cooling transition affects
the cooling mechanism. In order to model the atom-laser interaction, the whole level structure of the D2 line has to be taken into account. Two different regimes have been recognized, one optimizing the loading of the trap, the
second minimizing the temperature of the atoms. We investigated these two regimes experimentally and found results in agreement
with the theoretical predictions.
Received: 6 March 1998 / Received in final form: 13 May 1998 / Accepted: 13 May 1998 相似文献
5.
S. Wallentowitz R.L. de Matos Filho S.-C. Gou W. Vogel 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,6(3):397-405
We present a method for the direct measurement of the Wigner-function matrix for complex vibronic states of a trapped atom,
that is suited to analyse the entanglement between two motional degrees of freedom and the internal electronic dynamics. It
is a generalisation of the method for the determination of vibronic quantum states [S. Wallentowitz, R.L. de Matos Filho,
W. Vogel, Phys. Rev. A 56, 1205 (1997)] in conjunction with the scheme for the direct observation of the Wigner function of a single motional degree
of freedom [L.G. Lutterbach, L. Davidovich, Phys. Rev. Lett. 78, 2547 (1997)]. The major advantage of the present method is that it reduces the experimental efforts substantially. On the
other hand, it is demonstrated that the nonlinear vibronic coupling necessary for this method turns out to be its main limitation.
Received: 5 August 1998 相似文献
6.
L. Sanchez-Palencia P. Horak G. Grynberg 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(3):353-364
We numerically study the spatial diffusion of an atomic cloud experiencing Sisyphus cooling in a three-dimensional linlin optical lattice in a broad range of lattice parameters. In particular, we investigate the dependence on the size of the
lattice sites which changes with the angle between the laser beams. We show that the steady-state temperature is largely independent
of the lattice angle, but that the spatial diffusion changes significantly. It is shown that the numerical results fulfill
the Einstein relations of Brownian motion in the jumping regime as well as in the oscillating regime. We finally derive an
effective Brownian motion model from first principles which gives good agreement with the simulations.
Received 8 August 2001 and Received in final form 6 November 2001 相似文献
7.
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
8.
H. Koibuchi 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,59(1):55-62
Nambu-Goto model is investigated by using the canonical Monte Carlo simulation technique on dynamically triangulated surfaces
of spherical topology. We find that the model has four distinct phases; crumpled, branched-polymer, linear, and tubular. The
linear phase and the tubular phase appear to be separated by a first-order transition. It is also found that there is no long-range
two-dimensional order in the model. In fact, no smooth surface can be seen in the whole region of the curvature modulus α,
which is the coefficient of the deficit angle term in the Hamiltonian. The bending energy, which is not included in the Hamiltonian,
remains large even at sufficiently large α in the tubular phase. On the other hand, the surface is spontaneously compactified
into a one-dimensional smooth curve in the linear phase; one of the two degrees of freedom shrinks, and the other degree of
freedom remains along the curve. Moreover, we find that the rotational symmetry of the model is spontaneously broken in the
tubular phase just as in the same model on the fixed connectivity surfaces. 相似文献
9.
M. Gangl H. Ritsch 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,8(1):29-40
We develop quantum models for the combined external and internal motion of atoms in a strongly coupled driven cavity mode
including the transverse degrees of freedom. Using a simplified Gaussian mode function we determine the parameter regimes
and prospects of 3D cooling and confinement of one or two atoms in the cavity field. Analysing the field dynamics for slow
atoms traversing the cavity, we show that the spectrum of the transmitted and spontaneously scattered light contains ample
information on the motional dynamics of the atom and can be nicely used to investigate the cooling properties of the system.
Including several atoms in the dynamics we show how motional correlations build up by the common interaction with the cavity
field. This can be looked upon as collisions at far distance and can be monitored via the transmitted field dynamics.
Received 5 March 1999 and Received in final form 4 May 1999 相似文献
10.
F. Levi A. Godone J. Vanier S. Micalizio G. Modugno 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,12(1):53-59
The paper is concerned with the line shapes of resonance phenomena observed in Coherent Population Trapping (CPT) applied
to alkali atoms in a cell containing a buffer gas. Significant asymmetries and departures from a Lorentzian shape have been
observed in connection with the measurement of dark lines and CPT maser emission profiles. Measurements are reported as a
function of the power and frequency tuning of the laser used to create the CPT phenomenon. The paper reports on different
experimental conditions and a comparison between theory and experiments is made for the cases of cesium and rubidium in a
buffer gas.
Received 3 March 2000 and Received in final form 10 April 2000 相似文献
11.
H. Koibuchi 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,59(3):405-411
A surface model of Nambu and Goto is studied statistical mechanically by using the canonical Monte Carlo simulation technique
on a spherical meshwork. The model is defined by the area energy term and a one-dimensional bending energy term in the Hamiltonian.
We find that the model has a large variety of phases; the spherical phase, the planar phase, the long linear phase, the short
linear phase, the wormlike phase, and the collapsed phase. Almost all two neighboring phases are separated by discontinuous
transitions. It is also remarkable that no surface fluctuation can be seen in the surfaces both in the spherical phase and
in the planar phase. 相似文献
12.
H. Koibuchi 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,52(2):265-273
A first-order phase transition is found in two types of intrinsic curvature models defined on dynamically triangulated surfaces
of disk topology. The intrinsic curvature energy is included in the Hamiltonian. The smooth phase is separated from a non-smooth
phase by the transition. The crumpled phase, which is different from the non-smooth phase, also appears at sufficiently small
curvature coefficient α. The phase structure of the model on the disk is identical to that of the spherical surface model,
which was investigated by us and reported previously. Thus, we found that the phase structure of the fluid surface model with
intrinsic curvature is independent of whether the surface is closed or open. 相似文献
13.
H. Koibuchi 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,57(3):321-330
Two types of surface models have been investigated by Monte Carlo simulations on triangulated spheres with compartmentalized
domains. Both models are found to undergo a first-order collapsing transition and a first-order surface fluctuation transition.
The first model is a fluid surface one. The vertices can freely diffuse only inside the compartments, and they are prohibited
from the free diffusion over the surface due to the domain boundaries. The second is a skeleton model. The surface shape of
the skeleton model is maintained only by the domain boundaries, which are linear chains with rigid junctions. Therefore, we
can conclude that the first-order transitions occur independent of whether the shape of surface is mechanically maintained
by the skeleton (=the domain boundary) or by the surface itself. 相似文献
14.
Brimicombe PD Roberts NW Jaradat S Southern C Wang ST Huang CC Dimasi E Pindak R Gleeson HF 《The European physical journal. E, Soft matter》2007,23(3):281-287
A binary mixture of an antiferroelectric liquid-crystal material containing a selenium atom and a highly chiral dopant is
investigated using resonant X-ray scattering. This mixture exhibits a remarkably wide four-layer intermediate smectic phase,
the structure of which is investigated over a temperature range of 16K. Analysis of the resonant X-ray scattering data allows
accurate measurement of both the helicoidal pitch and the distortion angle as a function of temperature. The former decreases
rapidly as the SmC
* phase is approached, whilst the latter remains constant over the temperature range studied at 8°±3° . We also observe that the senses of the helicoidal pitch and the unit cell of the repeating four-layer structure are opposite
in this mixture and that there is no pitch inversion over the temperature range studied. 相似文献
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16.
Studies performed on strong polyelectrolytes and on a weak polyelectrolyte, sodium poly(acrylate), show that their stability
in presence of multivalent cations depends on the chemical nature of the charged side groups of the polymer. For sulfonate
groups (SO3
-) or sulfate groups (OSO3
-) phase separation generally occurs in presence of inorganic cations of valency 3 (as La3+) or larger and a resolubilization takes place at high salt concentration. The interactions of the polyelectrolyte with multivalent
cations are of electrostatic origin and the phase diagrams are weakly dependent on the chemical nature of the polymer backbone
and on the specificity of the counterions. For acrylate groups, (COO-), the phase separation was observed with inorganic cations of valency 2 (as Ca2+) or larger without resolubilization at high salt concentration. The phase separation is due to a chemical association between
cations and acrylate groups of two neighboring monomers of the same chain. This chemical association creates a hydrophobic
complex by dehydrating both monomer and cation. With organic trivalent cation, as spermidine +H3N(CH2)4NH2
+(CH2)3NH3
+, where no chemical association occurs with the charged side groups COO- or SO3
- of the polyelectrolyte, similar phase diagrams were observed whatever was the polyelectrolyte with a resolubilization at
high trivalent cation concentration.
Received 3 March 1999 and Received in final form 2 September 1999 相似文献
17.
F. Li W. X. Shu J. G. Jiang H. L. Luo Z. Ren 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(2):355-361
Spatiotemporal dynamics of Bose-Einstein condensates in
moving optical lattices have been studied. For a weak lattice
potential, the perturbed correction to the heteroclinic orbit in a
repulsive system is constructed. We find the boundedness
conditions of the perturbed correction contain the Melnikov
chaotic criterion predicting the onset of Smale-horseshoe chaos.
The effect of the chemical potential on the spatiotemporal
dynamics is numerically investigated. It is revealed that the
variance of the chemical potential can lead the systems into
chaos. Regulating the intensity of the lattice potential can
efficiently suppress the chaos resulting from the variance of the
chemical potential. And then the effect of the phenomenological
dissipation is considered. Numerical calculation reveals that the
chaos in the dissipative system can be suppressed by adjusting the
chemical potential and the intensity of the lattice potential. 相似文献
18.
M.-H. Du L.-L. Wang A. Kolchin H.-P. Cheng 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):323-326
The interaction of water with SiO
2 is an important problem in geophysics,
materials physics, and environmental science. In this paper, we
present recent results on studies of H
2
O-silica clusters from first-principles
Born-Oppenheimer molecular dynamics calculations. Bond strength
and chemical stability are investigated as a function of cluster
size and chemical composition. Both physisorption and
chemisorption of water molecules on the clusters are discussed
via analysis of energetics.
Calculations of clusters are compared with the results from
extended surfaces. The validity of clusters as models of
surfaces is discussed. 相似文献
19.
C.F. Lo 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,1(1):93-95
Based upon the hidden Lie SU(1,1) symmetry, we have constructed the unitary decoupling transformation which diagonalizes the
multimode two-quantum Jaynes-Cummings model and provides us with an extremely convenient basis to gain a deeper understanding
of the dressing processes present in the matter-field interaction. This canonical transformation approach is very simple and
can be easily extended to other generalized Jaynes-Cummings models.
Received: 5 July 1997 / Revised: 3 November 1997 / Accepted: 14 November 1997 相似文献
20.
J. H. Li X. X. Yang 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,53(4):449-454
We analyze hybrid absorptive-dispersive optical bistability (OB)
behavior via tunable Fano-type interference based on intersubband
transitions in asymmetric double quantum wells (QWs) driven
coherently by a probe laser field by means of a unidirectional
ring cavity. We show that OB can be controlled efficiently by
tuning the energy splitting of the two excited states (the
coupling strength of the tunnelling), the Fano-type interference,
and the frequency detuning. The influence of the electronic
cooperation parameter on the OB behavior is also discussed. This
investigation may be used for optimizing and controlling the
optical switching process in the QW solid-state system, which is
much more practical than that in atomic system because of its
flexible design and the controllable interference strength. 相似文献