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101.
D.V. Fisher Y. Maron 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,14(3):349-359
Accurate treatment of the plasma density effects requires a detailed knowledge of the spatial distribution of individual ions
around a test ion. In the present work, rigorous expressions are derived for the main 2- and 3-particle spatial distribution
functions involving the nearest neighbor (NN) and the next-nearest neighbor (NNN) ions. These expressions, valid for both
ideal and nonideal plasmas, present the distributions as functionals of the potentials U
NN and U
NNN at the nearest and next-nearest ion locations. All of the distribution functions except one are derived and discussed in
the present work for the first time ever. For utilization of our results in practical calculations, we suggest semi-empirical
expressions for U
NN and U
NNN in the ion-ion coupling parameter range 0 ?Γ < 1. In order to test the accuracy of our expressions for U
NN and U
NNN we conduct Molecular Dynamics (MD) simulations. The simulations utilize the pure Coulomb particle-particle interaction potentials,
regularized at close range to avoid classical Coulomb collapse, and are free from the assumptions made to find U
NN and U
NNN. Thus, the results of the MD simulations provide an independent test of our theoretical results. Excellent agreement has
been found between the results of the theory and of the MD simulations. Finally, we outline the implications of the present
findings on the problem of tunneling and charge exchange in dense plasmas.
Received 27 October 2000 and Received in final form 30 January 2001 相似文献
102.
Jeong Junho Briere Tina M. Sahoo N. Das T. P. Ohira Seiko Nishiyama K. Nagamine K. 《Hyperfine Interactions》2001,136(3-8):769-775
The trapping sites for muon and muonium in ferromagnetic p-Cl–Ph–CH=N–TEMPO [(4-(p-chlorobenzylideneamino)–TEMPO (TEMPO = 2,6,6-tetramethyl-piperidin-1-yloxyl)]
and the hyperfine interaction tensors for these sites are obtained using first-principles Unrestricted Hartree–Fock theory.
The calculated hyperfine interactions are used to compare the calculated zero field muon spin rotation (μSR) frequencies for
different choices for the easy axis and the observed frequency. It has been concluded that the two trapping centers that can
best explain the observed μSR frequency are a trapped singlet muonium near the radical oxygen and a trapped muon site near
the chlorine. The direction of the easy axis also is determined to be the b-axis of the monoclinic lattice. This direction for the easy axis is confirmed by determining the direction of the distributed
magnetization in the molecular solid which leads to a minimum dipole–dipole interaction energy. The consequences of this agreement
for the easy axis direction by two independent procedures are discussed.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
103.
M.N. Mineva M. Hellström M. Bernas J. Gerl H. Grawe M. Pfützner P.H. Regan M. Rejmund D. Rudolph F. Becker C.R. Bingham T. Enqvist B. Fogelberg H. Gausemel H. Geissel J. Genevey M. Górska R. Grzywacz K. Hauschild Z. Janas I. Kojouharov Y. Kopatch A. Korgul W. Korten J. Kurcewicz M. Lewitowicz R. Lucas H. Mach S. Mandal P. Mayet C. Mazzocchi J.A. Pinston Zs. Podolyàk H. Schaffner Ch. Schlegel K. Schmidt K. Sümmerer H.J. Wollersheim 《The European Physical Journal A - Hadrons and Nuclei》2001,11(1):9-13
Rapidity correlations in 800 GeV proton interactions with emulsion nuclei are investigated for different targets and multiplicity
regions. To study the energy dependence, the results have been compared with proton interactions at 200 GeV and 400 GeV. A
common feature of all the interactions is the existence of strong, short-range correlations. However, no dependence of cluster
parameters on primary energy or target mass is found. A marginal increase of correlation strength with multiplicity is observed.
Received: 30 March 2001 / Accepted: 18 September 2001 相似文献
104.
E. García-Matres J.L Martínez J. Rodríguez-Carvajal 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,24(1):59-70
A neutron diffraction study, as a function of temperature, of the title compounds is presented. The whole family (space group
Immm, a
≈ 3.8?, b
≈ 5.8?, c
≈ 11.3?) is structurally characterised by the presence of flattened NiO6 octahedra that form chains along the a-axis, giving rise to a strong Ni-O-Ni antiferromagnetic interaction. Whereas for Y-compound only strong 1D correlations exist
above 1.5 K, presenting the Haldane gap characteristic of 1D AF chain with integer spin, 3D AF ordering is established simultaneously
for both R and Ni sublattices at temperatures depending on the rare earth size and magnetic moment. The magnetic structures
of R2BaNiO5 ( R
=
Nd, Tb, Dy, Ho, Er and Tm) have been determined and refined as a function of temperature. The whole family orders with a magnetic
structure characterised by the temperature-independent propagation vector
= (1/2, 0, 1/2). At 1.5 K the directions of the magnetic moments differ because of the different anisotropy of the rare earth ions. Except
for Tm and Yb (which does not order above 1.5 K), the magnetic moment of the R3+ cations are close to the free-ion value. The magnetic moment of Ni2+ is around 1.4
, the strong reduction with respect to the free-ion value is probably due to a combination of low-dimensional quantum effects
and covalency. The thermal evolution of the magnetic structures from T
N
down to 1.5 K is studied in detail. A smooth re-orientation, governed by the magnetic anisotropy of R3+, seems to occur below and very close to T
N
in some of these compounds: the Ni moment rotates from nearly parallel to the a-axis toward the c-axis following the R moments. We demonstrate that for setting up the 3D magnetic ordering the R-R exchange interactions cannot
be neglected.
Received 19 July 2001 相似文献
105.
R. Ramakumar K. Yamaji 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,24(1):71-75
A simple model is developed to understand superconductivity in α
′
-TTF[Pd(dmit)2]2. We include electron-intra molecular and intermolecular phonon interactions as the mechanism of superconductivity. Intramolecular vibrations included are the eight symmetric Ag modes of the Pd(dmit)2 molecule. Intermolecular vibrations included are the longitudinal acoustic and transverse acoustic (LA and TA) modes of the Pd(dmit)2 column. All the electron-phonon coupling constants are calculated from first principles. We find that largest el-intramolecular vibration coupling is to the Ag mode with the highest frequency (1449 cm-1). The el-intermolecular coupling to the LA mode is found to be larger than the total el-intramolecular couplings. We also find el-(TA)phonon coupling to be at least an order of magnitude smaller than el-(LA)phonon coupling.
Estimate of superconducting transition temperature is comparable to experimental result. We also provide a detailed discussion,
employing the results of recent numerical calculations on two-chain Hubbard model and the specific material parameters, on
the relative importance of el-ph and Coulomb-origin mechanisms of superconductivity in α
′
-TTF[Pd(dmit)2]2 and TTF[Ni(dmit)
2
]
2
.
Received 29 March 2001 and Received in final form 7 August 2001 相似文献
106.
研究了在美国BNL/AGS上能量10.7AGeV的197Au离子诱发核作用,报告了EMU–01国际合作实验关于射弹核碎裂和产生粒子密度等最新实验结果. 相似文献
107.
The processes of electron transfer and dissociative scattering are explored for collisions of hyperthermal NO+ on GaAs(110). The experiments reveal a marked angular dependence to O− emergence. A strong correlation between the O− scattering angle and the final atom-surface interaction site provides a map of the lateral dependence to reactivity. The results are modeled by sequential neutralization, dissociation, and electron attachment steps. Classical trajectory calculations, in conjunction with an empirical opacity function, accurately reproduce the experimental results. The opacity function is interpreted as the probability that an electron will attach to a departing O fragment as a function of the last surface site the atom impacts. The experiments indicate that O− emergence occurs predominantly for oxygen atoms which come in close contact with the localized dangling bond states of GaAs(110). 相似文献
108.
G. Duchateau E. Cormier R. Gayet 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,11(2):191-196
A simple theoretical approach based on Coulomb-Volkov states is introduced to predict ionisation of atoms by intense laser
pulses in cases where the effective interaction time does not exceed one or two optical cycles [M. Nisoli et al., Opt. Lett. 22, 522 (1997)]. Under these conditions, the energy distributions of ejected electrons predicted by this non-perturbative approach
are in very good agreement with “exact" results obtained by a full numerical treatment. The agreement is all the better that
the principal quantum number of the initial state is high. For very strong fields, most electrons are ejected at an energy
which is close to the classical kinetic energy that would be transferred to free electrons by the electromagnetic field during
the pulse. The power of the present approach appears when keV. In this region, full numerical treatments become very lengthy and finally do not converge. However, the present Coulomb-Volkov
theory still makes reliable predictions in very short computer times.
Received 19 November 1999 and Received in final form 19 January 2000 相似文献
109.
Well-defined (101) and (001) surfaces of anatase TiO2 were studied for the first time by secondary-electron imaging and low-energy electron diffraction. Initially, both surfaces show a crystalline structure corresponding to the bulk anatase phase, buried under an atomically thin contamination layer. After mild sputtering with 500 eV Ne+ ions, we have observed a surface phase transition from tetragonal anatase to face-centered cubic titanium monoxide TiO. Subsequent annealing at 900 K restores the (1×1) anatase structure at the (101) surface. On the (001) surface, however, a (1×4) reconstruction appears. The unreconstructed structure can be recovered by exposing the surface to oxygen. These observations demonstrate the stability of the anatase surfaces and illustrate the feasibility of preparing and investigating clean surfaces of this technological important form of TiO2. 相似文献
110.
S. von Rotz M.P. Locher V.E. Markushin 《The European Physical Journal A - Hadrons and Nuclei》2000,7(2):261-269
We evaluate three meson doorway mechanisms for nucleon-antinucleon annihilation at rest for the first time. Detailed results
are presented for the final state φπ0 originating from the 3S1 initial state and for the φρ channel originating from 1S0. The results presented also include the improved contributions from two meson doorway states and from the tree diagrams.
For all the channels considered a consistent explanation of large and small OZI violations emerges.
Received: 22 December 1999 相似文献