共查询到20条相似文献,搜索用时 31 毫秒
1.
I.M. Sokolov 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,22(3):369-373
We consider two-particle dispersion in a velocity field, where the relative two-point velocity scales according to v
2(r) ∝r
α and the corresponding correlation time scales as τ(r) ∝r
β, and fix α = 2/3, as typical for turbulent flows. We show that two generic types of dispersion behavior arize: For α/2 +
β < 1 the correlations in relative velocities decouple and the diffusion approximation holds. In the opposite case, α/2 +
β > 1, the relative motion is strongly correlated. The case of Kolmogorov flows corresponds to a marginal, nongeneric situation.
In this case, depending on the particular parameters of the flow, the dispersion behavior can be rather diffusive or rather
ballistic.
Received 13 March 2001 相似文献
2.
A. Díaz-Sánchez A. Pérez-Garrido 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,24(4):483-486
The relaxation of the specific heat and the entropy to their equilibrium values is investigated numerically for the three-dimensional
Coulomb glass at very low temperatures. The long time relaxation follows a stretched exponential function, f (t) = f
0exp - (t/τ)β
, with the exponent β increasing with the temperature. The relaxation time diverges as an Arrhenius law when T→ 0.
Received 24 May 2001 and Received in final form 12 September 2001 相似文献
3.
X.-J. Wang J.-H. Jiang M.-L. Yan 《The European Physical Journal A - Hadrons and Nuclei》2002,14(2):219-224
In terms of effective field theory and mixed-propagator approach, we show that there is a larger hidden effect of isospin
breaking in ρ→πγ decay due to a ω exchange, ρ→ω→πγ. The branching ratio is predicted as B(ρ→πγ) = (11.67±2.0)×10-4, which is much larger than Particle Data Group's datum (6.8±1.7)×10-4 and one of charged mode, B(ρ±→π±γ) = (4.5±0.5)×10-4.
Received: 7 January 2002 / Accepted: 2 April 2002 相似文献
4.
X.Q. Huang R.W. Peng F. Qiu S.S. Jiang A. Hu 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,23(3):275-281
We study in this paper, with the context of a tight-binding on-side model, the electronic properties of one-dimensional random
lattices with correlated impurities. We show that, when symmetrical impurities
are inserted in a host chain of site energy and a constant hopping interaction V, diffusion will occur even when is random. We provide analytic expressions for the transmittance and confirm the theoretical results by a great deal of numerical
calculations. When = V, we find that the mean-square displacement (MSD) follows the law
m
2
∝t
β with β = 2.0 for = constant and β = 1.0 for = = random, respectively.
Received 15 January 2001 and Received in final form 30 April 2001 相似文献
5.
K. Kossert M. Camen F. Wissmann J. Ahrens J.R.M. Annand H.-J. Arends R. Beck G. Caselotti P. Grabmayr O. Jahn P. Jennewein M.I. Levchuk A.I. L'vov J.C. McGeorge A. Natter V. Olmos de León V.A. Petrun'kin G. Rosner M. Schumacher B. Seitz F. Smend A. Thomas W. Weihofen F. Zapadtka 《The European Physical Journal A - Hadrons and Nuclei》2003,16(2):259-273
Differential cross-sections for quasi-free Compton scattering from the proton and neutron bound in the deuteron have been
measured using the Glasgow/Mainz photon tagging spectrometer at the Mainz MAMI accelerator together with the Mainz [48]cm
;SPMOslash; × [64]cm NaI(Tl) photon detector and the G?ttingen SENECA recoil detector. The data cover photon energies ranging from [200]MeV
to [400]MeV at θLAB
γ = 136.2°. Liquid deuterium and hydrogen targets allowed direct comparison of free and quasi-free scattering from the proton. The neutron
detection efficiency of the SENECA detector was measured via the reaction p(γ,π+
n). The “free” proton Compton scattering cross-sections extracted from the bound proton data are in reasonable agreement with
those for the free proton which gives confidence in the method to extract the differential cross-section for free scattering
from quasi-free data. Differential cross-sections on the free neutron have been extracted and the difference of the electromagnetic
polarizabilities of the neutron has been determined to be αn - βn = 9.8±3.6(stat)+2.1
-1.1(syst)±2.2(model) in units of [10-4]fm
3. In combination with the polarizability sum αn + βn = 15.2±0.5 deduced from photoabsorption data, the neutron electric and magnetic polarizabilities, αn = 12.5±1.8(stat)+1.1
-0.6(syst)±1.1(model) and βn = 2.7±1.8(stat)+0.6
-1.1(syst)±1.1(model) are obtained. The backward spin polarizability of the neutron was determined to be γ(n)
π = (58.6±4.0)×10-4
fm
4.
Received: 21 August 2002 / Accepted: 16 October 2002 / Published online: 11 February 2003
RID="a"
ID="a"Part of the Doctoral Thesis.
RID="b"
ID="b"Present address: Physikalisch-Technische Bundesanstalt, Bundesallee 100, D-38116 Braunschweig.
RID="a"
ID="a"Part of the Doctoral Thesis.
RID="b"
ID="b"Present address: Physikalisch-Technische Bundesanstalt, Bundesallee 100, D-38116 Braunschweig.
RID="c"
ID="c"Part of the Habilitation Thesis.
RID="d"
ID="d"e-mail: schumacher@physik2.uni-goettingen.de
Communicated by Th. Walcher 相似文献
6.
Alessandro Torcini Paolo Politi 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,25(4):519-529
Surface growth models may give rise to instabilities with mound formation whose typical linear size L increases with time (coarsening process). In one dimensional systems coarsening is generally driven by an attractive interaction
between domain walls or kinks. This picture applies to growth models for which the largest surface slope remains constant
in time (corresponding to model B of dynamics): coarsening is known to be logarithmic in the absence of noise ( L(t) ∼ ln t) and to follow a power law ( L(t) ∼t
1/3) when noise is present. If the surface slope increases indefinitely, the deterministic equation looks like a modified Cahn-Hilliard
equation: here we study the late stages of coarsening through a linear stability analysis of the stationary periodic configurations
and through a direct numerical integration. Analytical and numerical results agree with regard to the conclusion that steepening
of mounds makes deterministic coarsening faster : if α is the exponent describing the steepening of the maximal slope M of mounds ( M
α∼L) we find that L(t) ∼t
n: n is equal to for 1≤α≤2 and it decreases from to for α≥2, according to n = α/(5α - 2). On the other side, the numerical solution of the corresponding stochastic equation clearly shows that in the
presence of shot noise steepening of mounds makes coarsening slower than in model B: L(t) ∼t
1/4, irrespectively of α. Finally, the presence of a symmetry breaking term is shown not to modify the coarsening law of model
α = 1, both in the absence and in the presence of noise.
Received 28 September 2001 and Received in final form 21 November 2001 相似文献
7.
J. Huikari M. Oinonen A. Algora J. Cederkäll S. Courtin P. Dessagne L. Fraile S. Franchoo H. Fynbo W.X. Huang A. Jokinen A. Knipper F. Marechal C. Miehé E. Nacher K. Peräjärvi E. Poirier L. Weissman J. Äystö 《The European Physical Journal A - Hadrons and Nuclei》2003,16(3):359-363
The β-decay of 75Sr to its mirror nucleus 75Rb was studied at the ISOLDE PSB facility at CERN by means of β-delayed γ and proton spectroscopy. The decay Q-value and β-delayed γ intensity were measured for the first time. These results, 10.60±0.22 MeV and 4.5+1.9
-0.7%, together with accurate measurements of the β-decay half-life and β-delayed proton branching ratio yielded the Gamow-Teller
strength 0.35±0.05 for the mirror transition. Implications of the results on studies of deformation effects and on the path
of the rapid proton capture process are discussed.
Received: 26 September 2002 / Accepted: 30 October 2002 / Published online: 18 February 2003
RID="a"
ID="a"e-mail: jussi.huikari@phys.jyu.lfi
Communicated by D. Schwalm 相似文献
8.
F.P. Heßberger S. Hofmann I. Kojouharov D. Ackermann S. Antalic P. Cagarda B. Kindler B. Lommel R. Mann A.G. Popeko S. Saro J. Uusitalo A.V. Yeremin 《The European Physical Journal A - Hadrons and Nuclei》2002,15(3):335-342
The radioactive decay of 217Pa was investigated by means of α-γ-spectroscopy. Fine structure in the ground-state α-decay was established. Ambiguities
in the fine structure of the α-decay of the previously known isomeric state could be clarified by α-γ-coincidence measurements.
A previously unknown α-transition of E
α = (8306 ± 5) keV was detected and identified by means of delayed α-α- and α-γ-γ-coincidence measurements. A second isomeric
state decaying by α-emission was not observed. The quality of the previously reported data of the α-decay fine structure of
217Th was improved.
Received: 29 April 2002 / Accepted: 17 June 2002 / Published online: 19 November 2002
RID="a"
ID="a"e-mail: f.p.hessberger@gsi.de
Communicated by J. ?yst? 相似文献
9.
S. Leenhardt O. Sorlin M.G. Porquet F. Azaiez J.C. Angélique M. Belleguic C. Borcea C. Bourgeois J.M. Daugas C. Donzaud I. Deloncle J. Duprat A. Gillibert S. Grévy D. Guillemaud-Mueller J. Kiener M. Lewitowicz S.M. Lukyanov F. Marie N.A. Orr Yu.-E. Penionzhkevich F. de Oliveira Santos F. Pougheon M.G. Saint-Laurent W. Shuying Yu. Sobolev J.S. Winfield 《The European Physical Journal A - Hadrons and Nuclei》2002,14(1):1-5
The reduced transition probability B(E2: 01
+→ 2+) of 72Zn has been measured for the first time by Coulomb excitation at intermediate energy. The result B(E2: 01
+→ 2+) = 1740±210 e2fm4, corresponds to the deformation parameter β2 of 0.23, in close agreement with expectations derived from the neighboring nucleus 73Zn. A discussion of the evolution of the N = 40 sub-shell closure as a function of Z is presented.
Received: 19 December 2001 / Accepted: 14 March 2002 相似文献
10.
Y. Fujita H. Fujita T. Adachi G.P.A. Berg E. Caurier H. Fujimura K. Hara K. Hatanaka Z. Janas J. Kamiya T. Kawabata K. Langanke G. Martınez-Pinedo T. Noro E. Roeckl Y. Shimbara T. Shinada S.Y. van der Werf M. Yoshifuku M. Yosoi R.G.T. Zegers 《The European Physical Journal A - Hadrons and Nuclei》2002,13(4):411-418
Under the assumption that isospin is a good quantum number, symmetry is expected for the transitions from the ground states
of T = 1, T
z = ±1 nuclei to the common excited states of the T
z = 0 nucleus situated between the two nuclei. The symmetry can be studied by comparing the strengths of Gamow-Teller (GT)
transitions obtained from a (p, n)-type charge-exchange reaction on a target nucleus with T
z = 1 with those from the β-decay of the T
z = - 1 nucleus. The A = 58 system is the heaviest for which such a comparison is possible. As a part of the symmetry study, we measured the GT
transitions from 58Ni (T
z = 1) to 58Cu (T
z = 0) by using the zero-degree (3
He, t) reaction at 150 MeV/nucleon. With the achieved resolution of 50 keV, many hitherto unresolved GT states have been identified.
The GT transition strengths were obtained for states up to 8 MeV excitation, i.e., near to the Q window limitation ( Q
EC = 9.37 MeV) of the β-decay from 58Zn (T
z = - 1) to 58Cu. The strength distribution is compared with that from shell-model calculations.
Received: 24 November 2001 / Accepted: 30 January 2002 相似文献
11.
M. Hiane J. Ebothé 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,22(4):485-495
We show that the electrodeposition of Ni-Zn alloys at the lowest growth velocities, v < 0.5μm/s, exclusively proceeds from an abnormal co-deposition phenomenon. The growth process in this v region greatly depends on the initial [Co2+] concentration of the film deposition bath. A theoretical approach of this process including the role of the saturation surface
roughness of the alloy, , leads to an estimation of the transport properties of the ad-atoms involved during the deposit formation. Their surface
diffusion coefficient varying between 1.76×10-10 and 2.40×10-8 cm-2/s exhibits a minimal value, D
s = 2.10×10-10 cm-2/s located between v = 0.17 and 0.35μm/s. The spatial scaling analysis of the local roughness, σ, examined according to the power-law σ≈L
α reveals that the resulting roughness exponents concurs with the Kardar-Parisi-Zhang dynamics including the restricted surface
diffusion. Two main v regions leads to different fractal textural features of the alloy film surface. Below 0.10 μm/s, the roughness exponent obtained
is α≈ 0.6, depicting a limited ad-atom mobility. Over v = 0.30μm/s, this exponent stabilises at α≈ 0.82, indicating an increase of the surface diffusion.
Received 16 August 2000 and Received in final form 20 June 2001 相似文献
12.
J. Walls J. Clarke S. Cauchi G. Karkas H. Chen W.A. van Wijngaarden 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,14(1):9-13
Polarizabilities of several rubidium states were determined by measuring stark shifts of transitions using an electro-optically
modulated laser beam to excite an atomic beam. The voltage required for atoms excited by the laser beam in an electric field
to be simultaneously in resonance as atoms excited by a frequency sideband of the laser in a field free region was measured.
The scalar α
and tensor α
2
polarizabilities were found to be: α
(9
S
1/2
) = 103.77±0.09, α
(10
S
1/2
) = 272.54±0.16, α
(8
D
3/2
) = 230.68±0.25 and α
2
(8
D
3/2
) = 26.55±0.10, α
(8
D
5/2
) = 222.68±0.14 and α
2
(8
D
5/2
) = 51.91±0.10 MHz/(kV/cm)2. The results are 100 times more accurate than previous measurements and are within 1% of those found theoretically using
a Coulomb approximation calculation.
Received 7 September 2000 and Received in final form 6 December 2000 相似文献
13.
S.?Dey S.S.?Dasgupta C.C.?Dey P.?Bhattacharya 《The European Physical Journal A - Hadrons and Nuclei》2003,16(2):193-197
A kinematically complete experiment has been performed to study the α-n final-state interaction (FSI) in the α + d ↦α + p
+ n break-up reaction at 50 MeV incident energy for the alpha-particles. For this, we have chosen four pairs of correlation
angles for the outgoing alpha and protons. These are ( θα = 18°, θp = 42°), ( θα = 20°, θp = 45°), ( θα = 22°, θp = 42°) and ( θα = 22°, θp = 47°), selected kinematically where the allowed phase spaces are in favor of the α-n final-state interaction. Our experimental
data show strong α-n FSI in all the selected configurations. Also, the FSI is found to be stronger at the lower alpha-particle
energy when two FSI peaks appear in the same configuration.
Received: 17 June 2002 / Accepted: 3 October 2002 / Published online: 4 February 2003
RID="a"
ID="a"e-mail: dey_s2001@yahoo.com; Present address: 445 Waupelani Drive, Apt. F3, State College, PA 16801, USA.
Communicated by M. Gar?on 相似文献
14.
M. Martínez J.-L. Pichard 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(1):93-100
The two dimensional crossover from independent particle towards collective motion is studied using 2 polarized electrons (spinless
fermions) interacting via a U/r Coulomb repulsion in a L×L square lattice with periodic boundary conditions and nearest neighbor hopping t. Three regimes characterize the ground state when U/t increases. Firstly, when the fluctuation Δr of the spacing r between the two particles is larger than the lattice spacing a, there is a scaling length L
0 = π2(t/U) such that the relative fluctuation Δr/〈r〉 is a universal function of the dimensionless ratio L/L
0, up to finite size corrections of order L-2. L < L
0 and L > L
0 are respectively the limits of the free particle Fermi motion and of the correlated motion of a Wigner molecule. Secondly,
when U/t exceeds a threshold U
*(L)/t, Δr becomes smaller than a, giving rise to a correlated lattice regime where the previous scaling breaks down and analytical expansions in powers of
t/U become valid. A weak random potential reduces the scaling length and favors the correlated motion.
Received 28 March 2002 Published online 19 November 2002 相似文献
15.
T. Faestermann R. Schneider A. Stolz K. Sümmerer E. Wefers J. Friese H. Geissel M. Hellström P. Kienle H.-J. Körner M. Mineva M. Münch G. Münzenberg C. Schlegel K. Schmidt P. Thirolf H. Weick K. Zeitelhack 《The European Physical Journal A - Hadrons and Nuclei》2002,15(1-2):185-188
Neutron deficient nuclei near 100Sn have been produced by fragmentation of a 1 .
AGeV 112Sn beam. The fragments were separated, identified and stopped in a highly segmented silicon strip detector stack. This detector
measured the total energy of emitted β+-particles. γ-radiation was measured with surrounding detectors. The half-lives for many nuclides have been determined for
the first time and give important information for the following topics: For the heaviest particle-stable odd-odd nuclei 90Rh, 94Ag and 98In we observed for the first time fast β-decays, compatible with superallowed Fermi transitions and confirmed such decays
for 78Y, 82Nb and 86Tc. We have also observed long-lived T = 0 states in some of these nuclei. We measured the half-lives of all rp-process waiting-point nuclei from 80Zr up to 92, 93Pd. In addition we find the proton drip line nucleus 77Y to decay dominantly via β-decay. To study the Gamov-Teller strength in the β-decay near the doubly magic 100Sn we measured the half-life, β- and γ-spectrum of 102Sn. We propose a level scheme for the daughter nuclide 102In and deduce the Gamov-Teller strength (B
GT = 4.0±0.6). This is one of the largest values known.
Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002
RID="a"
ID="a"e-mail: thomas.faestermann@ph.tum.de 相似文献
16.
C. Tsallis D. Prato C. Anteneodo 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(4):605-611
We consider a statistical mixture based on that of two identical harmonic oscillators which is characterized by four parameters,
namely, the concentrations (x and y) of diagonal and nondiagonal bipartite states, and their associated thermal-like noises (T/α and T, respectively). The fully random mixture of two spins 1/2 as well as the Einstein-Podolsky-Rosen (EPR) state are recovered
as particular instances. By using the conditional nonextensive entropy as introduced by Abe and Rajagopal, we calculate a
bound for the separable-entangled frontier. Although this procedure is known to provide a necessary but in general not sufficient condition for separability, it does recover, in the particular case x = T = 0 ( ∀α), the 1/3 exact result known as Peres' criterion. The x = 0 frontier remarkably resembles to the critical line associated with standard diluted ferromagnetism where the entangled
region corresponds to the ordered one and the separable region to the paramagnetic one. The entangled region generically shrinks
for increasing T or increasing α.
Received 18 April 2002 / Received in final form 11 July 2002 Published online 31 October 2002
RID="a"
ID="a"e-mail: celia@cbpf.br 相似文献
17.
Yu.N. Novikov H. Schatz P. Dendooven R. Béraud Ch. Miehé A.V. Popov D.M. Seliverstov G.K. Vorobjev P. Baumann M.J.G. Borge G. Canchel Ph. Desagne A. Emsallem W. Huang J. Huikari A. Jokinen A. Knipper V. Kolhinen A. Nieminen M. Oinonen H. Penttilä K. Peräjärvi I. Piqueras S. Rinta-Antila J. Szerypo Y. Wang J. Äystö 《The European Physical Journal A - Hadrons and Nuclei》2001,11(3):257-261
A careful investigation of the isomeric transition of the long-lived state at 228.5 keV excitation energy in 80Y has been done. The HIGISOL facility at the Jyv?skyl? isochronous cyclotron has been used. We used the electron magnetic
transporter to prepare an appropriate source and to measure the electron spectra in clean background conditions. The measured
internal conversion coefficient αK = 0.50±0.07 allows unambiguous 1- identification for the 228.5 keV first excited isomeric state in 80Y. With a “bare" half-life of 6.8±0.5 s found in this work, this state is strongly populated in the rp-process during X-ray
bursts and has therefore to be taken into account in X-ray burst model calculations. However, because of the similarity of
the β-decay half-lives of isomeric and ground states, we find a maximum reduction in the effective β-decay lifetime of 80Y of only 17±2%. Our results pave the way for a future investigation of the impact of the isomeric state on the “effective"
80Y proton capture rate.
Received: 14 March 2001 / Accepted: 10 July 2001 相似文献
18.
V. Olmos de León F. Wissmann P. Achenbach J. Ahrens H.-J. Arends R. Beck P.D. Harty V. Hejny P. Jennewein M. Kotulla B. Krusche V. Kuhr R. Leukel J.C. McGeorge V. Metag R. Novotny A. Polonski F. Rambo A. Schmidt M. Schumacher U. Siodlaczek H. Ströher A. Thomas J. Weiß M. Wolf 《The European Physical Journal A - Hadrons and Nuclei》2001,12(2):207-215
Differential cross-sections for Compton scattering from the proton have been measured at the MAMI tagged photon facility using
the TAPS setup. The data cover an angular range of θlab
γ = 59°-155° and photon energies ranging from 55 MeV to 165 MeV. Our results are in good agreement with those from previous experiments,
but yield higher precision. Using dispersion relations the proton polarizabilities have been determined to be = [11.9±0.5stat.±1.3syst.±0.3mod.] . 10-4
fm
3 and = [1.2±0.7stat.±0.3syst.±0.4mod.)] . 10-4
fm
3. These results confirm the Baldin sum rule which was re-evaluated to be + = [13.8±0.4] . 10-4
fm
3. We can also conclude that there is no significant additional asymptotic contribution to the backward spin polarizability
γπ beyond the t-channel π0-exchange.
Received: 9 January 2001 / Accepted: 13 February 2001 相似文献
19.
C.M. Horowitz E.V. Albano 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,31(4):563-569
The relationship between a microscopic parameter p, that is related to the probability of choosing a mechanism of deposition, and the stochastic equation for the interface's
evolution is studied for two different models. It is found that in one model, that is similar to ballistic deposition, the
corresponding stochastic equation can be represented by a Kardar-Parisi-Zhang (KPZ) equation where both λ and ν depend on
p in the following way: ν(p) = νp and λ(p) = λp
3/2. Furthermore, in the other studied model, which is similar to random deposition with relaxation, the stochastic equation
can be represented by an Edwards-Wilkinson (EW) equation where ν depends on p according to ν(p) = νp
2. It is expected that these results will help to find a framework for the development of stochastic equations starting from
microscopic details of growth models.
Received 26 August 2002 / Received in final form 20 November 2002 Published online 6 March 2003
RID="a"
ID="a"e-mail: ealbano@inifta.unlp.edu.ar 相似文献
20.
H.W. Diehl M. Smock 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,21(4):567-587
A class of continuum models with a critical end point is considered whose Hamiltonian [φ,ψ] involves two densities: a primary order-parameter field, φ, and a secondary (noncritical) one, ψ. Field-theoretic methods
(renormalization group results in conjunction with functional methods) are used to give a systematic derivation of singularities
occurring at critical end points. Specifically, the thermal singularity ∼ | t|2 - α of the first-order line on which the disordered or ordered phase coexists with the noncritical spectator phase, and the coexistence
singularity ∼ | t|1 - α or ∼ | t|β of the secondary density <ψ> are derived. It is clarified how the renormalization group (RG) scenario found in position-space
RG calculations, in which the critical end point and the critical line are mapped onto two separate fixed points
CEP
* and
λ
*, translates into field theory. The critical RG eigenexponents of
CEP
* and
λ
* are shown to match.
CEP
* is demonstrated to have a discontinuity eigenperturbation (with eigenvalue y = d), tangent to the unstable trajectory that emanates from
CEP
* and leads to
λ
*. The nature and origin of this eigenperturbation as well as the role redundant operators play are elucidated. The results
validate that the critical behavior at the end point is the same as on the critical line.
Received 18 January 2001 相似文献