共查询到20条相似文献,搜索用时 15 毫秒
1.
Th. Pospischil P. Bartsch D. Baumann R. Böhm K. Bohinc M. Ding S. Derber M.O. Distler D. Elsner I. Ewald J. Friedrich J.M. Friedrich S. Grözinger S. Hedicke P. Jennewein J. Jourdan M. Kahrau F. Klein K.W. Krygier J. Lac A. Liesenfeld S. Malov J. McIntyre H. Merkel P. Merle U. Müller R. Neuhausen M. Potokar R.D. Ransome D. Rohe G. Rosner J. Sanner H. Schmieden M. Seimetz S. Širca I. Sick O. Strähle A. Süle A. Wagner Th. Walcher M. Weis 《The European Physical Journal A - Hadrons and Nuclei》2001,12(1):125-127
The polarization transfer from longitudinally polarized electrons to protons in the elastic scattering p(
e, e'
p) has been measured around Q2 = 0.4 (GeV/c)2 with the three-spectrometer facility at the Mainz microtron MAMI. From this polarization transfer the ratio G
Ep/(G
Mp/μp) has been determined. The ratio is found to be slightly less than unity in agreement with recent results from other laboratories
and from the Rosenbluth separation of cross-sections measured with unpolarized electrons.
Received: 26 July 2001 / Accepted: 25 September 2001 相似文献
2.
F.G. Kondev M.A. Riley T.B. Brown R.M. Clark M. Devlin P. Fallon D.J. Hartley I.M. Hibbert D.T. Joss D.R. LaFosse R.W. Laird F. Lerma M. Lively P.J. Nolan N.J. O'Brien E.S. Paul J. Pfohl D.G. Sarantites R.K. Sheline S.L. Shepherd J. Simpson R. Wadsworth 《The European Physical Journal A - Hadrons and Nuclei》1998,2(3):249-251
The quadrupole moment for the πg
9/2⊗νh
11/2 band in the 130>Pr nucleus has been measured using the Doppler-shift attenuation method. A centroid shift analysis was carried out and a value
of Q0=6.1±0.4 eb, corresponding to an axial prolate deformation of β2=0.35(3), has been determined. This is the first direct experimental confirmation of the deformation-driving character of
the πg
9/2 orbital in an odd-odd nucleus in the A≃135 superdeformed region.
Received: 23 April 1998 相似文献
3.
Hartmann L Gorbatschow W Hauwede J Kremer F 《The European physical journal. E, Soft matter》2002,8(2):145-154
The molecular dynamics in thin films (18 nm-137 nm) of isotactic poly(methyl methacrylate) (i-PMMA) of two molecular weights
embedded between aluminium electrodes are measured by means of dielectric spectroscopy in the frequency range from 50 mHz
to 10 MHz at temperatures between 273 K and 392 K. The observed dynamics is characterized by two relaxation processes: the
dynamic glass transition (α-relaxation) and a (local) secondary β-relaxation. While the latter does not depend on the dimensions
of the sample, the dynamic glass transition becomes faster (≤2 decades) with decreasing film thickness. This results in a
shift of the glass transition temperature T
g to lower values compared to the bulk. With decreasing film thickness a broadening of the relaxation time distribution and
a decrease of the dielectric strength is observed for the α-relaxation. This enables to deduce a model based on immobilized
boundary layers and on a region displaying a dynamics faster than in the bulk. Additionally, T
g was determined by temperature-dependent ellipsometric measurements of the thickness of films prepared on silica. These measurements
yield a gradual increase of T
g with decreasing film thickness. The findings concerning the different thickness dependences of T
g are explained by changes of the interaction between the polymer and the substrates. A quantitative analysis of the T
g shifts incorporates recently developed models to describe the glass transition in thin polymer films.
Received 12 August 2001 and Received in final form 16 November 2001 相似文献
4.
Z. Rudy W. Cassing L. Jarczyk B. Kamys P. Kulessa O.W.B. Schult A. Strzałkowski 《The European Physical Journal A - Hadrons and Nuclei》1999,5(2):127-129
It is shown that the mass dependence of the Λ-lifetime in heavy hypernuclei is sensitive to the ratio of neutron-induced
to proton-induced non-mesonic decay rates R
n/R
p. A comparison of the experimental mass dependence of the lifetimes with the calculated ones for different values of R
n/R
p leads to the conclusion that this ratio is larger than 2 on the confidence level of 0.75. This suggests that the phenomenological
ΔI= 1/2 rule might be violated for the nonmesonic decay of the Λ-hyperon.
Received: 31 March 1999 相似文献
5.
The KNΛ and KNΣ coupling constants have been calculated in the framework of the Chiral Bag Model(CBM). We find −3.88 ≤g
KNΛ≤−3.67 and 1.15 ≤g
KNΣ≤ 1.24 by taking into account pseudoscalar mesons (π, K) and vector mesons (ρ, ω, K
*) field effects. Particularly, it is shown that vector mesons make significant contributions to the coupling constants g
KNΛ and g
KNΣ. Our values are existing within the experimental limits compared to the phenomenological values extracted from the kaon photoproduction
and kaon-nucleon scattering experiments. Also, form factors are suggested for the πNN, πNΔ, KNΛ and KNΣ couplings.
Received: 17 August 1998 / Revised version: 22 December 1998 相似文献
6.
R. Kumar D. Mehta N. Singh H. Kaur A. Görgen S. Chmel R.P. Singh S. Murlithar 《The European Physical Journal A - Hadrons and Nuclei》2001,12(1):5-8
The band structures built on the 5- isomeric state ( T
1/2 = 3.46 m) in the doubly odd 130Cs nucleus have been established up to I = 24? via the 124Sn(11B, 5n)130Cs reaction. The previously observed bands based on the πh
11/2⊗νh
11/2, πg
7/2⊗νh
11/2 and πd
5/2⊗νh
11/2 configurations and a positive-parity side band with multiple connections to the α = 0 signature partner of the yrast πh
11/2⊗νh
11/2 band have been extended to higher spins. A new band based on the πh
11/2⊗νg
7/2 configuration is observed. The yrast πh
11/2⊗νh
11/2 band exhibits anomalous signature splitting whose magnitude decreases up to spin 15 and then increases without restoring
the normal signature splitting.
Received: 20 February 2001 / Accepted: 9 May 2001 相似文献
7.
U. Leinberger E. Berdermann F. Heine S. Heinz O. Joeres P. Kienle I. Koenig W. Koenig C. Kozhuharov A. Schröter H. Tsertos C. Hofmann G. Soff 《The European Physical Journal A - Hadrons and Nuclei》1998,1(3):249-256
We present the first energy and angle resolved measurements of e+e−-pairs emitted from heavy nuclei (Z≥ 40) at rest by internal pair conversion (IPC) of transitions with energies of less than 2 MeV as well as recent theoretical
results using the DWBA method, which takes full account of relativistic effects, magnetic substates and finite size of the
nucleus. The 1.76 MeV E0 transition in 90Zr (90Sr source) and the 1.77 MeV M1 transition in 207Pb (207Bi source) have been investigated experimentally using the essentially improved setup at the double-ORANGE β-spectrometer
of GSI. The measurements prove the capability of the setup to cleanly identify the IPC pairs in the presence of five orders
of magnitude higher β− and γ background from the same source and to yield essentially background-free sum spectra despite the large background.
Using the ability of the ORANGE setup to directly determine the opening angle of the e+e−–pairs (Θe+e−), the angular correlation of the emitted pairs was measured within the range covered experimentally (40°≤Θe+e−≤ 180°). In the 90Zr case the correlation could be deduced for a wide range of energy differences E
Δ of the pairs (−530 keV ≤E
Δ≤ 530 keV). The 90Zr results are in good agreement with recent theory. The angular correlation deduced for the M1 transition in 207Pb is in strong disagreement with theoretical predictions derived within the Born approximation and shows almost isotropic
character. This is again in agreement with the new theoretical results.
Received: 22 April 1997 / Revised version: 16 December 1997 相似文献
8.
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
9.
H. Iwasaki T. Motobayashi H. Akiyoshi Y. Ando N. Fukuda H. Fujiwara Zs. Fülöp K. I. Hahn Y. Higurashi M. Hirai I. Hisanaga N. Iwasa T. Kijima A. Mengoni T. Minemura T. Nakamura M. Notani S. Ozawa H. Sagawa H. Sakurai S. Shimoura S. Takeuchi T. Teranishi Y. Yanagisawa M. Ishihara 《The European Physical Journal A - Hadrons and Nuclei》2002,13(1-2):55-58
Experimental studies on in-beam γ-ray spectroscopy using a 12Be radioactive beam are presented. Inelastic scattering of the neutron-rich 12Be nucleus on 208Pb, 12C, and (CH2)n targets has been studied by measuring de-excitation γ-rays in coincidence with scattered particles. The level schemes and
transition probabilities are determined for low-lying excited states in 12Be. The present paper presents a brief review of the spectroscopic results, which may be associated with the N = 8 shell quenching near the drip line.
Received: 1 May 2001 / Accepted: 4 December 2001 相似文献
10.
Lichang Yin Yunzuo Liu Jingbin Lu Guangyi Zhao Xianfeng Li Xiaoguang Wu Guangsheng Li Shuxian Wen Chunxiang Yang 《The European Physical Journal A - Hadrons and Nuclei》2001,11(4):379-383
High-spin states of 160Lu have been studied through the 144Sm( 19F, 3n) reaction. The previously known πh
11/2⊗υi
13/2 yrast band is extended from I
π = 21- to 25- and a four quasiparticle band with configuration πh
11/2[523]7/2 -⊗υh
9/2[521]3/2 -⊗ (υi
13/2)2 is reported.
Received: 21 May 2001 / Accepted: 19 July 2001 相似文献
11.
T. Hayakawa Y. Toh M. Oshima M. Matsuda Y. Hatsukawa J. Katakura H. Iimura T. Shizuma S. Mitarai M. Sugawara H. Kusakari Y.H. Zhang 《The European Physical Journal A - Hadrons and Nuclei》2002,15(3):299-302
High-spin states of 157Dy were investigated using in-beam γ-ray spectroscopy techniques with a 150Nd(12C, 5n) reaction. Three rotational bands with the h
9/2, i
13/2 and h
11/2 configurations were observed up to (43/2-), 53/2+ and 45/2-, respectively. Interband M1 transitions in the h
11/2 (high-Ω) band were also measured up to the highest-spin state. The high-spin states were well reproduced by calculations
using the tilted-axis-cranking model (TAC). The B(M1)/B(E2) ratio, Routhian and the tilted angle of the angular-momentum vector are found to be in good agreement with the result of
the TAC calculation.
Received: 22 August 2002 / Accepted: 26 September 2002 / Published online: 19 November 2002
RID="a"
ID="a"e-mail: hayakawa@jball4.tokai.jaeri.go.jp
Communicated by W. Henning 相似文献
12.
The phenomenological amplitude for the reaction πN→ππN fixed by fittings to the experimental data in the energy region 0.300 ≤P
Lab≤ 500 MeV/c is used for modelling the Chew–Low extrapolation and Olsson–Turner threshold approach. It is shown that the uncritical
application of the former results in enermous theoretical errors, the extracted values being in fact random numbers. The results
of the Olsson–Turner method are characterized by significant systematic errors coming from unknown details of the isobar physics.
Received: 10 December 1997 相似文献
13.
R. Krücken S.J. Asztalos R.M. Clark M.A. Deleplanque R.M. Diamond P. Fallon I.Y. Lee A.O. Macchiavelli G.J. Schmid F.S. Stephens K. Vetter Jing-Ye Zhang 《The European Physical Journal A - Hadrons and Nuclei》2001,10(2):151-155
High-spin states in 112Pd were studied using prompt γ-ray spectroscopy with Gammasphere following heavy-ion-induced fission in the reaction 18O + 208Pb at 91 MeV. A new 8+ level at 2638 keV was discovered with transitions connecting it to the yrast band and the quasi-gamma band. The three, now
established, closely spaced 8+ states indicate a mixing between the ground-state band, s-band, and quasi-gamma band. Several high-spin structures with likely negative parity have been extended to higher spin and
it is proposed that they are based on the νh
11/2(g
7/2
d
5/2) and νh
11/2(s
1/2
d
3/2) configurations.
Received: 28 November 2000 / Accepted: 8 February 2001 相似文献
14.
C. Muri R.M. Anjos R. Cabezas P.R.S. Gomes S.B. Moraes A.M.M. Maciel G.M. Santos J. Lubian M.M. Sant'Anna C. Tenreiro R. Liguori Neto J.C. Acquadro P.A.B. Freitas 《The European Physical Journal A - Hadrons and Nuclei》1998,1(2):143-149
Elastic and inelastic scattering differential cross sections were measured in the energy range 30 MeV ≤ E
lab
≤ 55 MeV, for the 14N +59Co system. Ambiguities of the optical potential derived from the analysis of the elastic scattering data were removed by performing
calculations at the radius of sensitivity and by comparison with the available fusion cross section data. A simultaneous analysis
of the three mechanisms was performed by coupled channel calculations, and a unique energy independent nuclear potential was
found to be able to fit the data. Discussions and comparisons concerning the optical model, the threshold anomaly, full and
approximated coupled channel calculations are presented.
Received: 6 February 1997 / Revised version: 1 August 1997 相似文献
15.
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
16.
Y.C. Shin M.K. Cheoun K.S. Kim T.K. Choi 《The European Physical Journal A - Hadrons and Nuclei》2002,14(1):87-93
A role of the axial-vector mesons, such as K1 and a1, on the emitted-photon spectrum in hot hadronic matter is studied through the channels πρ→a
1→πγ and Kρ→K
1→Kγ. Both channels could be dominant over the region lower than E
γ∼ 0.5 GeV, while the role of the K1 meson is diminished in the higher E
γ region. This study is carried out with an SU
L(3) ⊗SU
R(3) effective chiral Lagrangian which includes vector and axial-vector mesons systematically and explains well their hadronic
and radiative decays simultaneously.
Received: 8 August 2001 / Accepted: 4 February 2002 相似文献
17.
L. Chkhaidze T. Djobava L. Kharkhelauri M. Mosidze 《The European Physical Journal A - Hadrons and Nuclei》1998,1(3):299-306
A detailed study of pion production in central Mg-Mg collisions at a momentum of 4.3 GeV/c per incident nucleon was carried
out with use of the setup GIBS. The average kinematical characteristics of pions (multiplicity n
−, momentum P, transverse momentum P
T, emission angle Θ, rapidity Y) and corresponding distributions have been obtained. The experimental results have been compared with the predictions of
the Quark Gluon String Model (QGSM) and satisfactory agreement between the experimental data and the model has been found.
The QGSM reproduces also the dependence of average P
T on n
−.
The temperatures of π− mesons have been estimated in the rapidity interval of 0.5 ≤ Y ≤ 2.1. A satisfactory fit for π− mesons has been achieved by using a form involving two temperatures T
1 and T
2. It is found that the QGSM underestimates T
2 by (10−15)%.
The data have been analyzed using the transverse momentum technique. The observed dependence of the <P
x
′(Y)> on Y shows the S-shape behaviour. The slope at midrapidity F has been determined. The QGSM reproduces the <P
x> distribution satisfactorily, but underestimates the parameter F.
Received: 2 August 1997 / Revised version: 17 November 1997 相似文献
18.
H. Sagawa 《The European Physical Journal A - Hadrons and Nuclei》2002,13(1-2):87-92
I discuss first the effect of decoupling of extended wave functions and the coherence in the low-energy E1 strength in drip line nuclei 12Be and 13O, which are studied by large-scale shell model calculations including 3 ?ω configuration space. The calculated results are
compared to recent experimental data of Coulomb excitations. The quenching of the core polarization charges in drip line nuclei
is also discussed in relation to recent observations of quadrupole moments in B-isotopes.
Received: 1 May 2001 / Accepted: 4 December 2001 相似文献
19.
T. Ishii M. Asai A. Makishima I. Hossain P. Kleinheinz M. Ogawa M. Matsuda S. Ichikawa 《The European Physical Journal A - Hadrons and Nuclei》2002,13(1-2):15-19
Nuclei in the neutron-rich Ni region have been studied by γ-ray spectroscopy. Gamma-rays emitted from isomers, with T
1/2 > 1 ns, produced in heavy-ion deep-inelastic collisions were measured with an isomer-scope. The nuclear structure of the
doubly magic 68Ni and its neighbor 69,71Cu is discussed on the basis of the shell model. Future experiments for more neutron-rich Ni nuclei are also viewed.
Received: 1 May 2001 / Accepted: 4 December 2001 相似文献
20.
K.C. Chung C.S. Wang A.J. Santiago J.W. Zhang 《The European Physical Journal A - Hadrons and Nuclei》2001,12(2):161-167
The parameters of the σ-ω-ρ model in the relativistic mean-field theory with nonlinear σ-meson self-interaction are determined
by nuclear-matter properties, which are taken as those extracted by fits to data based on nonrelativistic nuclear models.
The values of the relevant parameters are C
σ
2∼ 94, C
ω
2∼ 32, C
ρ
2∼ 26, b∼ - 0.09, c∼ 1, and the σ-meson mass m
σ∼ 370 MeV, while the value of the calculated nuclear- surface thickness is t∼ 1.4 fm. The field system is shown to be stable, since the σ-meson self-interaction energy is a lower bound in this whole
parameter region with positive c. On the other hand, the effective nucleon mass M* is larger than 0.73M, if the symmetry incompressibility Ks is assumed to be negative and the nuclear-matter incompressibility K0 is kept less than 300 MeV.
Received: 27 June 2001 / Accepted: 5 October 2001 相似文献