共查询到19条相似文献,搜索用时 15 毫秒
1.
S. Heinz E. Berdermann F. Heine O. Joeres P. Kienle I. Koenig W. Koenig C. Kozhuharov U. Leinberger M. Rhein A. Schröter H. Tsertos 《The European Physical Journal A - Hadrons and Nuclei》1998,1(1):27-37
We present the results of a Doppler-shift correction to the measured e+e−–sum-energy spectra obtained from e+e−–coincidence measurements in 238U +206Pb and 238U +181Ta collisions at beam energies close to the Coulomb barrier, using an improved experimental setup at the double-Orange spectrometer
of GSI. Internal-Pair-Conversion (IPC) e+e− pairs from discrete nuclear transitions of a moving emitter have been observed following Coulomb excitation of the 1.844
MeV (E1) transition in 206Pb and neutron transfer to the 1.770 MeV (M1) transition in 207Pb. In the collision system 238U +181Ta, IPC transitions were observed from the Ta-like as well as from the U-like nuclei. In all systems the Doppler-shift corrected
e+e−–sum-energy spectra show weak lines at the energies expected from the corresponding γ–ray spectra with cross sections being
consistent with the measured excitation cross sections of the γ lines and the theoretically predicted IPC coefficients. No
other than IPC e+e−–sum-energy lines were found in the measured spectra. The transfer cross sections show a strong dependence on the distance
of closest approach (Rmin), thus signaling also a strong dependence on the bombarding energy close to the Coulomb barrier.
Received: 22 July 1997 / Revised version: 15 October 1997 相似文献
2.
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
3.
4.
P. Mason N. Marginean G. Montagnoli S. Beghini F. Scarlassara E. Farnea C. A. Ur A. Meroni A. M. Stefanini L. Corradi E. Fioretto I. V. Pokrovskiy B. Guiot A. Gadea J. J. Valiente-Dobón F. Della Vedova R. Orlandi E. Sahin D. R. Napoli L. Berti N. Toniolo S. Szilner M. Trotta M. Romoli M. La Commara D. Pierroutsakou M. Sandoli G. Pollarolo G. Benzoni 《The European physical journal. Special topics》2007,150(1):359-361
PRISMA is a magnetic
spectrometer installed at Laboratori Nazionali di Legnaro (Italy)
and designed for A=100–200, E=5–10 MeV-per-nucleon beams, and for
possible use with the proposed radioactive beam facility SPES. The
foremost features of the instrument are presented, along with the
outline of two data analyses exemplifying the effectiveness of
PRISMA-CLARA in studies of reaction
dynamics. 相似文献
5.
6.
B. Kämpfer O.P. Pavlenko S. Zschocke 《The European Physical Journal A - Hadrons and Nuclei》2003,17(1):83-87
QCD sum rules predict that the change of the strange quark condensate 〈ˉss〉 in hadron matter at finite baryon density causes a shift of the peak position of the di-electron spectra from φ-meson decays.
Due to the expansion of hadron matter in heavy-ion collisions, the φ peak suffers a smearing governed by the interval of density
in the expanding fireball, which appears as an effective broadening of the di-electron spectrum in the φ region. The emerging
broadening is sensitive to the in-medium change of 〈ˉss〉. This allows to probe directly in-medium modifications of 〈ˉss〉 via di-electron spectra in heavy-ion collisions at SIS energies with HADES.
Received: 22 November 2002 / Accepted: 30 January 2003 / Published online: 29 April 2003 相似文献
7.
T. Glasmacher B.V. Pritychenko P.D. Cottle R.W. Ibbotson K.W. Kemper H. Scheit 《The European Physical Journal A - Hadrons and Nuclei》2002,13(1-2):59-62
Projectile fragmentation provides radioactive beams at intermediate velocities (v/c = 0.3-0.5) by physical means of fragment separation. With the development of position-sensitive photon detectors it has become
possible to measure the energies and directions of photons emitted in-flight from such fast-moving exotic beams. This allows
the reconstruction of the photons' energies emitted from an exotic projectile with high accuracy. It can be advantageous to
employ photon detection in experiments with exotic beams since photons can traverse matter easily and their attenuation can
be calculated. Experiments with standard luminosities can be carried out at intermediate beam energies with thick secondary
targets (order of g/cm2) and very low incident beam rates (order of particle/s or less). Experimental success in this field is strongly correlated
with the development of photon detectors such as position-sensitive scintillation detectors or segmented germanium detectors.
In-beam gamma-ray spectroscopy of fast exotic beams has been successfully used at all projectile fragmentation facilities
in intermediate-energy heavy-ion inelastic scattering experiments, knockout reactions and fragmentation reactions. Here, we
focus on experimental results for neutron-rich exotic nuclei in the π(sd )-shell. Measurements and detector developments carried out at the NSCL at Michigan State University during the last four
years are discussed.
Received: 1 May 2001 / Accepted: 4 December 2001 相似文献
8.
9.
K. E. Stiebing K. A. Müller J. Baumann K. Bethge J. Bernhardt H. Bokemeyer H. Folger O. Fröhlich O. Hohn G. Kavermann G. Lambrinidis A. Müller J. Peter S. Runkel L. Schmidt H. Schmidt-Böcking P. Senger P. Thee J. Ullrich 《The European Physical Journal A - Hadrons and Nuclei》2000,8(1):87-96
The feasibility of the spectroscopy of dynamically ionized electrons (positrons) from heavy-ion collisions at intermediate
energies, e.g. Pb+Pb at 60 AMeV has been studied. We propose a magnetic toroid spectrometer for lepton spectroscopy in an energy range between 5 and 50
MeV. Special emphasis was laid on large solid angles, on broad-band characteristics and on a good suppression of secondary
events. The device is a versatile compact-size instrument for lepton detection in in-beam experiments at a moderate energy
resolution of %.
Received: 28 December 1999 / Accepted: 29 March 2000 相似文献
10.
I. Peter W. von Oertzen S. Thummerer H.G. Bohlen B. Gebauer J. Gerl M. Kaspar I. Kozhoukharov T. Kröll M. Rejmund H.J. Wollersheim I.J. Thompson 《The European Physical Journal A - Hadrons and Nuclei》2003,16(4):509-525
At energies below the Coulomb barrier, neutron transfer and Coulomb excitation have been measured in a very heavy asymmetric
nuclear system, in 206Pb + 118Sn. These are semi-magic nuclei showing super-fluid properties. Particle-γ coincidence techniques using 5 Euroball Cluster
detectors (EB), combined in a set-up with the Heidelberg-Darmstadt NaI Crystal Ball (CB), have been used. Position-sensitive
detectors allowed the observation of scattering processes covering angles from 110 up to 150 degrees. The fragments are identified
via the known γ-decays of the lowest excited states using the high resolution of EB. Using the unique feature of the set-up
with the CB, transfer to well-defined final channels with known quantum numbers is selected using the high-efficiency multiplicity
filter of the CB with no second γ-ray, i.e. without feeding. The data are analysed using the semi-classical approach and transfer probabilities are obtained. Coulomb
excitation has been analysed using known transition probabilities. The enhancement is deduced for the two-neutron transfer
populating the low-lying super-fluid 2+ states in 120Sn and 116Sn, while the 2n transition remains in the ground state for the 20NPb nuclei. Large enhancements up to EF ≃ 103 are observed. This is the first observation of neutron pair transfer enhancement for a heavy nuclear binary system with super-fluid
properties with experimentally separated levels. The calculations with microscopic 2-neutron wave functions, with configuration
mixing over six shell model configurations and using the coupled reaction channels approach, reproduce well the observed probabilities
and the enhancement.
Received: 27 August 2002 / Accepted: 9 December 2002 / Published online: 25 March 2003
RID="a"
ID="a"e-mail: oertzen@hmi.de
Communicated by D. Schwalm 相似文献
11.
A. T. Rudchik V. O. Romanyshyn E. I. Koshchy A. Budzanowski K. W. Kemper K. Rusek V. D. Chesnokova J. Choiński B. Czech L. Głowacka S. Kliczewski V. M. Kyryanchuk S. Yu. Mezhevych A. V. Mokhnach O. A. Momotyuk O. A. Ponkratenko R. Siudak I. Skwirczyńska A. Szczurek 《The European Physical Journal A - Hadrons and Nuclei》2007,33(4):317-325
Angular distributions of the 7Li + 10B elastic and inelastic scattering were measured at the energy E
lab (10B) = 51 MeV (21 MeV c.m.). These and previously measured 7Li + 10B elastic-scattering data known at the 7Li-beam energies 24 MeV (14.1 MeV c.m.) and 39 MeV (22.94 MeV c.m.) were analyzed within the optical model and coupled-reaction
channels method to determine the energy dependence of the parameters of the scattering potential and find the difference of
these parameters from that of 7Li + 11B scattering. It was found that the 7Li + 11B potential parameters fail to describe the 7Li + 10B scattering data. The biggest difference is observed between the depths of the imaginary potentials that describe these scatterings. 相似文献
12.
Yu.V. Pyatkov Yu.E. Penionzhkevich W.H. Trzaska O.I. Osetrov A.A. Alexandrov I.A. Alexandrova J. Äystö K.-Th. Brinkmann S.V. Khlebnikov V.F. Kushniruk A.V. Kuznetsov V.G. Lyapin V.A. Maslov M. Mutterer Z. Radivojevich V.A. Rubchenya Yu.G. Sobolev G.P. Tiourine D.N. Vakhtin 《The European Physical Journal A - Hadrons and Nuclei》2001,10(2):171-175
A pronounced fine structure (FS) in the form of distinct peaks was observed in neutron gated mass spectra from the decay of
the 278110 composite system produced in the reaction 238U + 40Ar (243 MeV) at an initial excitation energy E
* > 70 MeV. The FS peaks are located in the vicinity of mass numbers 70-80, 100, and 130, which correspond to those of magic
nuclei (clusters). In the data there is also evidence for a new type of decay -- collinear cluster tripartition of an excited
nucleus.
Received: 8 August 2000 / Accepted: 2 February 2001 相似文献
13.
R.I. Badran D.J. Parker I.M. Naqib 《The European Physical Journal A - Hadrons and Nuclei》2001,12(3):317-325
Excitation functions for the production of eight radioactive products of the reactions of 7Li on 56Fe have been measured up to E(7
Li) = 89 MeV. Recoil range distributions for these products, together with inclusive proton, deuteron, triton and alpha spectra,
have been measured at energies of 50 and 68 MeV. The α, t and d spectra show characteristic “break-up” components at forward
angles, while the recoil distributions show evidence of complete fusion and incomplete-fusion process 56Fe( 7Li,α) 59Co * . A parallel study on 55Mn shows some evidences of the ( 7Li,t) incomplete-fusion process, but the cross-section for this process is significantly less than for the triton fusion process.
The recoil distributions can be reproduced on the assumption that essentially all the observed break-up fragments are in fact
associated with incomplete fusion, but uncertainties in normalisation leave open the possibility of a significant contribution
of pure break-up. A diffraction model of the ( 7Li,α) transfer process reproduces the observed break-up α spectra with some success.
Received: 29 March 2001 / Accepted: 12 November 2001 相似文献
14.
G. Montagnoli S. Beghini F. Scarlassara A.M. Stefanini L. Corradi C.J. Lin G. Pollarolo Aage Winther 《The European Physical Journal A - Hadrons and Nuclei》2002,15(3):351-356
The two systems 40Ca + 90,96Zr have been studied by measuring nucleon transfer reactions at two energies near the Coulomb barrier, thus complementing
the available sub-barrier fusion cross-sections. Angular distributions for various transfer channels have been determined.
Significantly larger neutron transfer cross-sections are found for the target 96Zr that exhibits the larger enhancement in the sub-barrier fusion cross-sections. All data have been analyzed with a new model
for heavy-ion collisions that calculates simultaneously transfer cross-sections, fusion excitation functions and barrier distributions.
The model gives a good account of both transfer and fusion data.
Received: 2 May 2002 / Accepted: 4 June 2002 / Published online: 26 November 2002
RID="a"
ID="a"e-mail: montagnoli@pd.infn.it, Fax +39049 8277102, Tel. +39049 8277117.
RID="b"
ID="b"On leave from the China Institute for Atomic Energy, 102413 Beijing, China.
Communicated by C. Signorini 相似文献
15.
H. Ikezoe T. Ikuta S. Mitsuoka Y. Nagame I. Nishinaka K. Tsukada T. Ohtsuki T. Kuzumaki J. Lu 《The European Physical Journal A - Hadrons and Nuclei》1998,2(4):379-382
Mean lifetimes of the high spin states in the yrast band of 126Ba were measured by using the Doppler shift attenuation method in connection with the reaction 116Sn (16O, 2p4n)126Ba at a beam energy of 73 MeV. The corresponding normalized B(E2) values are obviously reduced in the vicinity of the backbending.
The results are compared with the theoretical predictions based on a realistic nucleon-nucleon interaction.
Received: 9 June 1997 / Revised version: 16 October 1997 相似文献
16.
A. T. Rudchik K. W. Kemper V. O. Romanyshyn O. A. Ponkratenko V. M. Kyryanchuk V. V. Uleshchenko 《The European Physical Journal A - Hadrons and Nuclei》2009,41(1):31-37
The data for the 7Li + 9Be and 7Be + 9Be elastic scattering at the energies E
lab(7Li) = 15.75 , 24, 30, 34, 63 and 130MeV and E
lab(7Be) = 17 , 19 and 21MeV were analyzed within the optical model and coupled-reaction-channels method. The elastic and inelastic
scattering, reorientation of 7Li , 7Be and 9Be as well as most important transfer reactions were included in the coupled-channels scheme. The resulting 7Li and 7Be potentials are very similar and have the same energy dependence. The real potential for recently derived 8Be + 9Be scattering potentials is very similar to that for 7Li , 7Be but the imaginary part of the 8Be one has a much greater strength at longer range. 相似文献
17.
P. von Brentano C. Fransen A. Gade A. Lisetskiy N. Pietralla 《The European Physical Journal A - Hadrons and Nuclei》2002,15(1-2):99-103
Due to the recent development of radioactive beam production, various direct reaction studies in reversed kinematics have
been made to investigate the behavior of the N = 20 shell closure in the neutron-rich region. Coulomb excitation, proton inelastic scattering, and fragmentation of unstable
nuclei have been studied with γ-ray detection.
Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002
RID="a"
ID="a"e-mail: motobaya@rikkyo.ne.jp 相似文献
18.
N. Ikeda F. Nakamura K. Mizuuchi T. Sugimitsu S. Teruyama T. Okamoto H. Fujita S. Morinobu 《The European Physical Journal A - Hadrons and Nuclei》2000,7(4):491-502
The 16O(13C,12C)17O reaction at 50 MeV has been investigated using the kinematical coincidence method. Polarization tensors t
20 and t
40 of 12C[2+
1] for the quantization axis taken along the direction of propagation have been measured by analyzing the energy spectrum of
12C[2+
1], modulated by the effect of γ ray emission. The deduced t
40 values significantly deviate from zero, contrary to the prediction of the distorted-wave Born approximation theory based
on one-step p shell neutron stripping without spin-dependent interactions. The phenomenological spin–orbit interaction necessary
to reproduce the magnitude of measured t
40 is found to be much larger than the folding model prediction. It is shown that the experimental polarization tensors as well
as the cross sections can be reproduced by introducing multi-step processes involving excitations in 12C and 13C without introducing spin-dependent interactions.
Received: 2 August 1999 / Revised version: 3 February 2000 相似文献
19.
G. Georgiev I. Matea D. L. Balabanski J. M. Daugas F. de Oliveira Santos S. Franchoo F. Ibrahim F. Le Blanc M. Lewitowicz G. Lo Bianco S. Lukyanov V. Meot P. Morel G. Neyens Yu. E. Penionzhkevich A. Saltarelli O. Sorlin M. Stanoiu M. Tarisien N. Vermeulen D. Verney D. Yordanov 《The European Physical Journal A - Hadrons and Nuclei》2006,30(2):351-356
We report a measurement of the g-factor of the I
π = 9/2+, t
1/2 = 22ns isomer in 65Ni. The state of interest was populated and spin-oriented using a single-neutron transfer on an enriched 64Ni target. The value, which was obtained, g(9/2+,65m
Ni) = - 0.296(3) is well in agreement with the g-factors of the other 9/2+ states in the region and with large-basis shell model calculations. The known g-factor of the 9/2+ isomer in 63Ni was used in order to verify the strength of the hyperfine field of Ni( Ni) at room temperature. 相似文献