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1.
H. Arenhövel W. Leidemann E.L. Tomusiak 《The European Physical Journal A - Hadrons and Nuclei》2002,14(4):491-509
Formal expressions are derived for the multipole expansion of the structure functions of a general polarization observable
of exclusive electrodisintegration of the deuteron using a longitudinally polarized beam and/or an oriented target. This allows
one to exhibit explicitly the angular dependence of the structure functions by expanding them in terms of the small rotation
matrices d
j
m'm(θ), whose coefficients are given in terms of the electromagnetic multipole matrix elements. Furthermore, explicit expressions
for the coefficients of the angular distributions of the differential cross-section including multipoles up to L
max = 3 are listed in tabular form.
Received: 19 November 2002 / Accepted: 7 May 2002 相似文献
2.
F. Zontone F. D'Acapito G. Faraci A.R. Pennisi 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,19(4):501-505
We report on the formation and detection of a compressed fluid phase of Xe clusters in as- implanted Si, at room temperature.
The simultaneous structural characterization of the Xe clusters and of the Si matrix was performed by X-ray diffraction at
grazing incidence coupled with two-dimensional detection; in both cases, the nearest-neighbor distance and the coordination
were obtained. In order to investigate the early stage of the atomic inclusion and the cluster segregation, the average compression
and size of Xe fluid clusters within the amorphous Si matrix were explained within the simple Hard Sphere model.
Received 4 September 2000 and Received in final form 13 December 2000 相似文献
3.
P. Roussel P. Foury-Leylekian B. Domengès D. Groult P. Labbé J.-P. Pouget 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,12(4):497-508
A new variety of P
4
W
10
O
38
, m
= 5 member of the monophosphate tungsten-bronze family with pentagonal tunnels (MPTB
p), , has been isolated and studied by X-ray diffraction measurements. The structure has been solved by direct methods from single
crystal X-ray data. The monoclinic unit cell corresponds to a regular stacking of WO
3
-type slabs which are all five-WO
6
-octahedra thick and connected through PO
4
tetrahedra. This structure is comparable to that previously described for the MPTB
p'series with m
= 4 (P
4
W
8
O
32
) and m
= 6 (P
4
W
12
O
44
). An X-ray diffuse scattering investigation has revealed that this member is subjected to charge density wave instabilities
(CDW) located on chains running along the directions. Two CDW transitions have been observed at and , bearing some resemblance with those exhibited by the m
= 4 member. The corresponding modulation wave vectors can be accounted for by a hidden nesting mechanism which connects the crossing
points of differently oriented quasi-planar Fermi surfaces, as found for the low m (4 and 6) members of the MPTB's.
Received 12 March 1999 and received in final form 20 May 1999 相似文献
4.
S.-M. Li J. Chen Z.-F. Zhou 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,19(2):157-163
Laser-assisted electron-atomic-hydrogen “elastic" scattering is studied in the first Born approximation. The initial and final
states of projectile electron are described by the Volkov wavefunctions; the dressed state of target described by a time-dependent
perturbative wavefunction in soft photon approximation. The laser modified cross-sections are calculated in two distinct geometries
for laser polarization either parallel or perpendicular to the incident direction of electron. The numerical results shows
that the multiphoton cross-sections oscillate by a few orders over the whole scattering angular region. The results for a
parallel geometry oscillate more frequently in the intermediate angles; while the results for a perpendicular geometry oscillate
more frequently in the forward and backward angles. At large scattering angles, the sum rule of Kroll and Watson is noticeably
violated. The laser modification on summed total cross-section increases with field strength, but decreases with field frequency
and polarization deviation from the incident direction.
Received 18 October 2001 and Received in final form 26 December 2001 相似文献
5.
D. O. Odero 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,19(1):3-8
The time-dependent treatment of positron-hydrogen scattering for a zero total angular momentum has been presented. The initial
wavefunction of the positron-hydrogen scattering system has been expanded in terms of three dimensional dynamical wave functions
to include all higher angular momenta by solving a set of three coupled differential equations. This wavefunction is then
time evolved using Taylor series expansion of the evolution operator. The excitation probabilities are monitored as the wavefunction
propagates until there is no more change in the probabilities. The positron impact excitation cross-sections extracted from
the final wavefunction are compared with the available results of converged close coupling approach.
Received 23 July 2001 and Received in final form 25 November 2001 相似文献
6.
S. Haffner M. Schmidt P.J. Benning C.G. Olson L.L. Miller D.W. Lynch 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,23(1):69-77
In recent years insight has been gained into the electronic structure of layered cuprates using angle-resolved photoelectron
spectroscopy. In many of these studies it is assumed that the electron-photon matrix element follows the trends set by the
atomic photoionization cross sections and does not influence lineshape, dispersion and the k-dependence of the spectral intensity. In this study using Sr2CuO2Cl2 as an example it will be shown that the electron-photon matrix element can have a strong impact on both strength and shape
of a feature in an angle-resolved photoelectron spectrum of a layered cuprate which can strongly affect information on character
and the momentum-dependence of the energy and spectral weight of a state deduced from the spectra. The results of this study
put an emphasis on the need to employ the whole parameter range of the ARPES method to get reliable information on the spectral
function of cuprates for which purpose synchrotron radiation is an uniquely suited tool.
Received 10 January 2000 and Received in final form 15 January 2001 相似文献
7.
A. Marucci P. Launois R. Moret A. Pénicaud 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(1):29-34
The phase diagram of the newly synthesized mixed crystal C60-biphenyl is investigated as a function of temperature by single-crystal X-ray scattering. Diffuse scattering investigations
evidencing complex disorder and local order effects are presented. Two phase transitions leading to two different doublings
of the high temperature unit cell are observed, at 212 K and 147 K. The first transition is attributed to the ordering of
twisted biphenyls, which couples to the orientational ordering of the C60 molecules as the temperature decreases. Full ordering of the C60 molecules is achieved below 100 K only, in the low temperature phase. The rich phase diagram of C60-biphenyl is due to the interplay between fullerene and biphenyl ordering phenomena.
Received 31 August 2001 and Received in final form 4 December 2001 相似文献
8.
T.J. Davis 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,14(3):289-297
The problem of atom diffraction from a reflecting magnetic diffraction grating is solved in the thin phase-grating approximation.
The general problem for scalar diffraction is modelled using a semi-classical method in which the grating potential is separated
into a reflecting term and a diffracting term. The trajectory of the atom in the reflecting potential is solved classically
and the atom wave function in the diffracting potential found by integrating the phase change along the classical trajectory.
The diffraction orders are obtained after Fourier transforming the result. This can be done independently of the grating potential
resulting in a general formula for the diffraction efficiencies. The general result is applied to the problem of atom diffraction
from a magnetic grating. Several approximations are required to reduce the problem to a form amenable to analytic solution.
The results are compared with an accurate numerical method.
Received 1st February 2001 and Received in final form 8 March 2001 相似文献
9.
F. Muller P. Fontaine M. Delsanti L. Belloni J. Yang Y.J. Chen J.W. Mays P. Lesieur M. Tirrell P. Guenoun 《The European physical journal. E, Soft matter》2001,6(2):109-115
The counterion distribution within a spherical polyelectrolyte sparse brush was measured by small-angle X-ray scattering using
contrast variation with different counterions by means of ion dialysis. The brush was made by self-association of charged
diblock copolymers. Thanks to the contrast variation method, we were able to separate the signal due to the monomers and the
signal due to the counterions. At a small length scale, it is demonstrated that the system behaves as independent charged
rods whose counterion distribution follows the Poisson-Boltzmann model.
Received 14 February 2001 and Received in final form 2 May 2001 相似文献
10.
A. Latz M. Letz 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,19(3):323-343
The theory of light scattering for a system of linear molecules with anisotropic polarizabilities is considered. As a starting
point for our theory, we express the result of a scattering experiment in VV and VH symmetry as dynamic correlation functions
of tensorial densities ρ
lm(q) with l = 0 and l = 2. l, m denote indices of spherical harmonics. To account for all observed hydrodynamic singularities, a generalization of the theory
of Schilling and Scheidsteger [1] for these correlation functions is presented, which is capable to describe the light scattering
experiments from the liquid regime to the glassy state. As a microscopic theory it fulfills all sum rules contrary to previous
phenomenological theories. We emphasize the importance of the helicity index m for the microscopic theory by showing, that only the existence of m = 1 components lead to the well known Rytov dip in liquids and to the appearance of transversal sound waves in VH symmetry
in the deeply supercooled liquid and the glass. Exact expressions for the phenomenological frequency dependent rotation translation
coupling coefficients of previous theories are derived.
Received 3 July 2000 and Received in final form 7 November 2000 相似文献
11.
G.G. Pereira 《The European physical journal. E, Soft matter》2002,7(3):273-289
The inherent nanoscale morphologies of self-organizing diblock copolymer melts are now being investigated for a variety of
technological applications. To obtain global, well-oriented, regular patterns requires suitably confining and aligning the
melt between two flat plates. Here we consider such confinement for an asymmetrical diblock melt, which forms columns of the
minority phase in a matrix of the majority phase. We investigate this system with a combination of numerical simulations and
strong segregation theory and make suggestions as to when perpendicular orientation should prevail over parallel orientation
of the columns.
Received 22 May 2001 and Received in final form 14 February 2002 相似文献
12.
R. Lefort B. Toudic J. Etrillard F. Guillaume P. Bourges R. Currat T. Breczewski 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,24(1):51-57
The diffraction pattern of n-alkane/urea inclusion compounds is known to contain a broad diffuse scattering related to the
molecular form factor of the alkane species, indicating individual rotational and/or translational disorder of these molecules.
Inelastic coherent neutron scattering reveals for the first time the entirely dynamical character of the alkane molecular
disorder around room temperature. This observation fully agrees with a recent model of the coherent scattering cross section
of totally uncorrelated motions. In the ordered phase this diffuse scattering remains, but elastic, and very low energy molecular
vibrational modes are evidenced. These observations are discussed in relation with previous incoherent neutron scattering
results.
Received 9 February 2001 and Received in final form 1st August 2001 相似文献
13.
R. Itri J. Depeyrot F.A. Tourinho M.H. Sousa 《The European physical journal. E, Soft matter》2001,4(2):201-208
Small-angle X-ray scattering (SAXS) was performed on a series of Electric Double-Layered Magnetic Fluids (EDL-MF) composed
of ferrite type-- CoFe2O4, MnFe2O4, ZnFe2O4, NiFe2O4 and CuFe2O4--nanoparticles of different crystalline sizes ( D
XR ranging from 40 to 139?, as determined by X-ray diffraction). The information concerning the scattering objects was obtained
through the analysis of the distance distribution function p(r) and of the size distribution function D(R), both retrieved from SAXS data. The results show that EDL-MF, in the absence of an applied magnetic field, are composed
of small magnetic particle aggregates in solution. These agglomerates are elongated in one direction (chain-like) with the
longest dimension varying from 240 to 330?. The cross-section size is of the order of D
XR. The data also demonstrate that the maximum dimension of these aggregates is independent of the ferrite type. On the other
hand, the number of aggregated magnetic particles is nanoparticle-size-dependent. Accordingly, larger ferrite-type nanoparticles
as those with D
XR = 139? form aggregates composed of 2-3 magnetic particles, whereas smaller ones with D
XR
40? form agglomerates of about 6 magnetic particles in solution. As the nanoparticle size is reduced, it might increase the
particle surface defects. Such occurrence would affect the particle surface charge density, which could reduce the electrostatic
screening, favoring the agglomeration phenomenon.
Received 28 February 2000 and Received in final form 28 August 2000 相似文献
14.
A. Pumir V.V. Barelko 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,22(1):71-77
Fronts of weakly exothermal chemical reaction may propagate in solids at very low temperatures ( 4K≤T≤77K) thanks to a quite unusual mechanism, involving a feedback between the heat produced by the reaction and the disruption of
the solid matrix. In this class of phenomena, the reaction may be induced by mechanical constraints, without a large elevation
of temperature. On the basis of a simple phenomenological model, we investigate ignition of a propagating front by initially
(i) disrupting a localized zone of the solid matrix, or by (ii) introducing a temperature jump, leading to a thermal shock
with strong temperature gradients. In particular, we show that reaction can be initiated by disrupting only a very small fraction
of the sample. Applications to the problem of initiation of solid explosives by friction or shocks is briefly discussed.
Received 26 January 2001 and Received in final form 3 May 2001 相似文献
15.
F.-R. Carminati M. Schiavoni L. Sanchez-Palencia F. Renzoni G. Grynberg 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,17(2):249-254
We present a detailed experimental study of a three-dimensional lin⊥lin bright optical lattice. Measurements of the atomic
temperature and spatial diffusion coefficients are reported for different angles between the lattice beams, i.e. for different lattice constants. The experimental findings are interpreted with the help of numerical simulations. In particular
we show, both experimentally and theoretically, that the temperature is independent of the lattice constant.
Received 5 July 2001 and Received in final form 13 August 2001 相似文献
16.
J. Lal D. Abernathy L. Auvray O. Diat G. Grübel 《The European physical journal. E, Soft matter》2001,4(3):263-271
We have studied the static and dynamic behaviour of magnetic colloidal systems (ferrofluids) by Small-Angle X-ray Scattering
(SAXS) and X-ray Photon Correlation Spectroscopy (XPCS). The main features of the novel XPCS technique will be illustrated
by data taken on a model system, colloidal silica spheres. We will then present the results obtained on an optically opaque
suspension of magnetic colloids (maghemite) in the wave vector range from 10-3 to 10-2?^-1. Translational diffusion in zero field and anisotropic diffusion under external magnetic fields will be discussed.
Received 9 August 1999 and Received in final form 26 July 2000 相似文献
17.
M. Dubiel S. Brunsch W. Seifert H. Hofmeister G.L. Tan 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):229-232
Ag particles of 3.9 and 5.1 nm mean size in silicate glasses were produced by ion exchange and subsequent annealing at 480
and 600 °C. These thermal treatments may induce stresses in matrix and particles in addition to the well known effect of surface atoms
because of the thermal expansion mismatch of both materials. Structural characterisation of the particles by high-resolution
electron microscopy revealed a size-dependent lattice dilatation quite opposite to the so far observed lattice contraction
of similar metal/glass composites. This result, confirmed by X-ray absorption spectroscopy at the Ag K-edge, is discussed
in terms of an Ag-Ag bond length increase near the particle surface. The temperature-dependent EXAFS spectra (10-300 K) indicate
an increased thermal expansion coefficient of the particles with an increased mean particle size calculated on the basis of
an anharmonic Einstein model. With that the bond length increase can be explained. The results can be interpreted by a combination
of both the particle size effects and the influence of the surrounding matrix.
Received 30 November 2000 相似文献
18.
The field-induced carrier redistribution between the subbands of a semiconductor superlattice is treated using the density
matrix approach. The unit cell of the superlattice consists of one quantum well with three occupied subbands. Carrier scattering
on polar-optical phonons is described within the microscopic bulk phonon model. At the tunneling resonance, an intrinsic population
inversion is observed. The temperature dependence of the population inversion is determined.
Received 25 October 2002 / Received in final form 27 November 2002 Published online 6 March 2003
RID="a"
ID="a"e-mail: kl@pdi-berlin.de 相似文献
19.
L.L. Salcedo 《The European Physical Journal A - Hadrons and Nuclei》2003,16(1):71-94
The multiscattering problem is studied in the matrix density formalism. We study how to isolate the quasi-classical degrees
of freedom in order to connect them with a cascade approach. The different problems that arise, as well as their possible
solutions, are discussed and exemplified with a pion-nucleus model.
Received: 24 May 2002 / Accepted: 25 July 2002 / Published online: 17 January 2003
RID="a"
ID="a"e-mail: salcedo@ugr.es
Communicated by A. Sch?fer 相似文献
20.
T.J. Davis 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,14(1):111-118
The diffraction of laser-cooled atoms from a spatially-periodic potential is modelled using rigorous coupled-wave analysis.
This numerical technique, normally applied to light-diffraction, is adapted for use with atomic de Broglie waves incident
on a reflecting diffraction grating. The technique approximates the potential by a large number of constant layers and successively
solves the complex eigenvalue problem in each layer, propagating the solution up to the surface of the grating. The method
enables the diffraction efficiencies to be calculated for any periodic potential. The results from the numerical model are
compared with the thin phase-grating approximation formulae for evanescent light-wave diffraction gratings and idealised magnetic
diffraction gratings. The model is applied to the problem of diffracting Rb atoms from a grating made from an array of permanent
magnets.
Received 13 June 2000 and Received in final form 15 December 2000 相似文献