共查询到20条相似文献,搜索用时 15 毫秒
1.
R. Płaneta W. Gawlikowicz A. Wieloch J. Brzychczyk T. Ciszek A.J. Cole P. Désesquelles K. Grotowski P. Hachaj S. Micek P. Pawłowski Z. Sosin D. Benchekroun E. Bisquer A. Chabane M. Charvet B. Cheynis A. Demeyer E. Gerlic A. Giorni D. Guinet D. Heuer P. Lautesse L. Lebreton A. Lléres M. Stern L. Vagneron J.B. Viano 《The European Physical Journal A - Hadrons and Nuclei》2001,11(3):297-304
The creation of hot Ca-like fragments was investigated in the 40Ca + 40Ca reaction at 35 AMeV. Using the AMPHORA 4π detector system, the primary projectile-like fragment was reconstructed and its
properties were determined. Both primary and secondary distributions are compared with the predictions of a Monte Carlo code
describing a heavy-ion collision as a two-step process. Some of the nucleons which are identified as participants in the first
step are transferred in the second step to these final states, which correspond on the average to the maximum value of entropy
(thermodynamic probability). The model allows for competition between mean-field effects and nucleon-nucleon interactions
in the overlap zone of the interacting nuclei. The analysis presented here suggests a thermalized source picture of the decay
of the projectile-like fragment. The validity of the reconstruction procedure for projectile-like fragments is discussed.
Received: 12 March 2001 / Accepted: 20 June 2001 相似文献
2.
G. Casini M. Bini S. Calamai R. Laforest P.R. Maurenzig A. Olmi G. Pasquali S. Piantelli G. Poggi F. Saint-Laurent J.C. Steckmeyer A.A. Stefanini N. Taccetti 《The European Physical Journal A - Hadrons and Nuclei》2000,9(4):491-513
Primary and secondary masses of heavy reaction products have been deduced from kinematics and E-ToF measurements, respectively,
for the direct and reverse collisions of 93Nb and 116Sn at 25 AMeV. Light charged particles have also been measured in coincidence with the heavy fragments. Direct experimental
evidence of the correlation of energy-sharing with net mass transfer has been found using information from both the heavy
fragments and the light charged particles. The ratio of hydrogen and helium multiplicities points to a further correlation
of angular momentum sharing with net mass transfer.
Received: 18 September 2000 / Accepted: 2 December 2000 相似文献
3.
L. Vannucci P. Boccaccio A. Bologna R.A. Ricci G. Vannini R. Donà I. Massa J.P. Coffin P. Fintz G. Guillaume F. Jundt F. Rami P. Wagner 《The European Physical Journal A - Hadrons and Nuclei》2000,7(1):65-77
Final states indicating the presence in the reaction of three-body fragmentation processes has been observed in 32S+59Co and 32S+63Cu dissipative collisions at 5.6 A · MeV. Besides the already observed sequential binary process, data analysis reveals the
presence of prompt ternary break-up of the composite system. Indications on the system configuration at the scission have
been deduced by analyzing the event shape in the momentum phase space. The decay appears to occur in a collinear configuration,
one of the produced fragments originating from the neck which connects the other two. In spite of the large energy dissipation,
structure effects in the charge partition seem to affect part of events.
Received: 3 July 1998 / Revised version: 15 October 1999 相似文献
4.
P. Pawłowski B. Borderie G. Auger Ch.O. Bacri N. Bellaize F. Bocage R. Bougault R. Brou P. Buchet J.L. Charvet A. Chbihi J. Colin D. Cussol R. Dayras A. Demeyer D. Doré D. Durand J.D. Frankland E. Galichet E. Genouin-Duhamel E. Gerlic D. Guinet P. Lautesse J.L. Laville J.F. Lecolley R. Legrain N. Le Neindre O. Lopez M. Louvel A.M. Maskay L. Nalpas A.D. Nguyen M. Pârlog J. Péter E. Plagnol M.F. Rivet E. Rosato F. Saint-Laurent S. Salou J.C. Steckmeyer M. Stern G. Tăbăcaru B. Tamain L. Tassan-Got O. Tirel E. Vient C. Volant J.P. Wieleczko 《The European Physical Journal A - Hadrons and Nuclei》2000,9(3):371-383
The prompt component at intermediate velocity of light charged particles is investigated. An improved coalescence model coupled
to the intra-nuclear cascade code ISABEL is used to obtain light complex particle energy spectra and multiplicities as a function
of impact parameter. The results are compared with experimental data from the 36Ar + 58Ni experiment at 95 MeV/nucleon, performed with the INDRA 4π detection system. The calculated prompt component is found to
rather well reproduce proton spectra. For complex light charged particles the calculated components well populate the high
energy part of spectra. Prompt emission can therefore explain the large transverse energies experimentally observed at mid-rapidity.
Received: 27 July 2000 / Accepted: 20 November 2000 相似文献
5.
Z. Sosin R. Płaneta T. Ciszek J. Brzychczyk W. Gawlikowicz K. Grotowski S. Micek P. Pawłowski A. Wieloch A.J. Cole D. Benchekroun E. Bisquer A. Chabane M. Charvet B. Cheynis A. Demeyer P. Désesquelles E. Gerlic A. Giorni D. Guinet D. Heuer P. Lautesse L. Lebreton A. Lléres M. Stern L. Vagneron J.B. Viano 《The European Physical Journal A - Hadrons and Nuclei》2001,11(3):305-310
The shape of the velocity distributions of charged particles projected on the beam direction can be explained if emissions
from the hot projectile-like fragment and the target-like fragment are supplemented by an emission from an intermediate velocity
source located between them. The creation of this source is predicted by a two-stage reaction model where, in the second stage,
some of the nucleons identified in the first stage as participants form a group of clusters located in the region between
the colliding nuclei. The cluster coalescence process is governed on the average by the maximum value of entropy, although
its fluctuations are also significant. The properties of the intermediate velocity source are precisely described, including
the isotopic composition of the emitted particles.
Received: 12 March 2001 / Accepted: 20 June 2001 相似文献
6.
Z. Sosin 《The European Physical Journal A - Hadrons and Nuclei》2001,11(3):311-317
We propose a two-stage, stochastic model of heavy-ion reactions. Nucleons becoming participants by mean-field effects or by
nucleon-nucleon interactions are transferred to definite final states, creating a PLF, a TLF, clusters, or escaping to continuum.
Nucleon transfer probabilities are governed by state densities. In this way different hot particle sources are created which
afterwards decay by particle emission.
Received: 12 March 2001 / Accepted: 20 June 2001 相似文献
7.
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
8.
We show that coalescence of nucleons emitted prior to thermalization in highly excited nuclei can explain the anomaly of
kinetic energies of helium clusters. A new coalescence algorithm has been included in the statistical approach to nuclear
reactions formerly used to describe intermediate mass fragment production.
Received: 24 September 1999 / Revised version: 22 November 1999 相似文献
9.
M. Pârlog G. Tăbăcaru J. P. Wieleczko J. D. Frankland B. Borderie A. Chbihi M. Colonna M. F. Rivet 《The European Physical Journal A - Hadrons and Nuclei》2005,25(2):223-228
Stochastic mean-field simulations for multifragmenting sources at the same excitation energy per nucleon have been performed. The freeze-out volume, a concept which needs to be precisely defined in this dynamical approach, was shown to increase as a function of three parameters: freeze-out instant, fragment multiplicity and system size. 相似文献
10.
We review experimental and theoretical studies devoted to extract information on the behaviour of the symmetry energy, in
density regions different from the normal value, with charge-asymmetric reactions at Fermi energies. In particular, we focus
on the analysis of fragmentation reactions and isotopic properties of the reaction products. Results concerning “isoscaling”
properties and the N/Z equilibration among the reaction partners in semi-peripheral reactions are also discussed. 相似文献
11.
E. Geraci U. Abbondanno L. Bardelli S. Barlini M. Bini M. Bruno F. Cannata G. Casini M. Chiari M. D'Agostino J. De Sanctis A. Giussani F. Gramegna V. L. Kravchuk A. L. Lanchais P. Marini A. Moroni A. Nannini A. Olmi A. Ordine G. Pasquali S. Piantelli G. Poggi G. Vannini 《The European physical journal. Special topics》2007,150(1):21-22
Symmetry energy is a key quantity in the study of the equation of state of asymmetric nuclear
matter. Heavy ion collisions at low and intermediate energies, performed at Laboratori Nazionali
di Legnaro and Laboratori Nazionali del Sud, can be used to extract information on the symmetry
energy coefficient Csym, which is currently poorly known but relevant both for astrophysics and
for deeper knowledge of the structure of exotic nuclei. 相似文献
12.
B. Borderie F. Gulminelli M.F. Rivet L. Tassan-Got M. Assenard G. Auger F. Bocage R. Bougault R. Brou Ph. Buchet J. Colin R. Dayras A. Demeyer J.D. Frankland E. Galichet E. Genouin-Duhamel E. Gerlic M. Germain D. Guinet P. Lautesse J.L. Laville J.F. Lecolley T. Lefort R. Legrain N. Le Neindre M. Louvel A.M. Maskay L. Nalpas A.D. Nguyen M. Parlog E. Plagnol A. Rahmani T. Reposeur E. Rosato F. Saint-Laurent S. Salou J.C. Steckmeyer M. Stern G. Tabacaru B. Tamain O. Tirel D. Vintache C. Volant 《The European Physical Journal A - Hadrons and Nuclei》1999,6(2):197-202
Vaporized sources produced in collisions between 36Ar and 58Ni at 95 MeV per nucleon have been detected with the multidetector INDRA. Complete information concerning the deexcitation
properties of quasi-projectiles, including second moments of chemical composition, is compared to a quantum statistical model
describing a gas of fermions and bosons in thermal and chemical equilibrium. Inclusions in the calculation of all known discrete
levels of nuclear species which deexcite into light particles and of a final state excluded volume interaction are found decisive
to very well reproduce the experimental data, which strongly supports that thermodynamical equilibrium was achieved at freeze-out
for such sources.
Received: 6 April 1999 相似文献
13.
R. V. Jolos A. K. Nasirov G. G. Adamian A. I. Muminov 《The European Physical Journal A - Hadrons and Nuclei》2000,8(1):115-124
The effect of shell structure on the distribution of the excitation energy between fragments of the deep inelastic collisions
is analysed in the microscopic approach. It is shown that the density of the single-particle levels of the proton and neutron
subsystems near the Fermi surface determines the ratio between the excitation energies of fragments at the initial stage of
the collision. It is shown also that the shell structure strongly influences the correlations between the width of the charge
distributions and the total kinetic energy losses. Calculations are performed for the 40,48Ca+248Cm reactions. The results obtained suggest a possible interpretation for the observed concentration of the excitation energy
in the light fragment in deep inelastic collisions for a wide range of the total kinetic energy losses.
Received: 27 July 1999 / Accepted: 29 March 2000 相似文献
14.
We aim to understand the role of momentum-dependent interactions in transverse flow as well as in its disappearance. For the
present study, central collisions involving masses between 24 and 394 are considered. We find that the momentum-dependent
interactions have different impact in lighter colliding nuclei compared to heavier colliding nuclei. In lighter nuclei, the
contribution of the mean field towards flow is smaller compared to heavier nuclei where binary nucleon-nucleon collisions
dominate the scene. The inclusion of momentum-dependent interactions also explains the energy of the vanishing flow in the
12C + 12C reaction which otherwise was not possible with the static hard equation of state. An excellent agreement of our theoretical
attempt is found for balance energy with experimental data throughout the periodic table. 相似文献
15.
M. Sandoli A. Boiano L. Campajola A. De Rosa A. D'Onofrio G. Inglima M. La Commara A. Ordine D. Pierroutsakou V. Roca M. Romano M. Romoli M. Trotta F. Rizzo F. Amorini S. Tudisco 《The European Physical Journal A - Hadrons and Nuclei》1999,6(3):275-288
We report on the results obtained from the study of the 32S +74Ge deep inelastic reaction at incident energy E= 320 MeV. High-energy γ-rays were detected in an array of 6 seven-pack BaF2 clusters. Coincidence with complex fragments detected in 12 three-stage telescopes ensured the selection of peripheral reaction
events. In order to investigate the pre-equilibrium dipole strength excitation two independent analyses were performed. In
the first analysis the energy spectra of the γ-rays were evaluated in the statistical model framework while in the second
one the γ-ray fragment angular correlation with respect to the nuclear spin vector of the composite system was studied. Both
methods indicate the excitation of dipole strength in the highly deformed dinucleus and provide dipole resonance parameter
sets that are in good agreement with each other.
Received: 24 March 1999 / Revised version: 17 May 1999 相似文献
16.
D. Pierroutsakou M. Di Toro F. Amorini V. Baran A. Boiano A. De Rosa A. D'Onofrio G. Inglima M. La Commara A. Ordine N. Pellegriti F. Rizzo V. Roca M. Romoli M. Sandoli M. Trotta S. Tudisco 《The European Physical Journal A - Hadrons and Nuclei》2003,16(3):423-435
We report on the results obtained from the study of the 32S + 64Ni and 32S + 58Ni peripheral reactions at incident energies E
lab = 288 MeV and E
lab = 320 MeV, respectively. High-energy γ-rays were detected in an array of 8 seven-pack BaF2 clusters. Coincidence with complex fragments detected in 12 three-stage telescopes ensured the selection of peripheral reaction
events. All of the relevant reaction parameters were kept constant with the exception of the different initial dipole moment
caused by the different entrance channel charge asymmetry. While for quasi-elastic events no N/Z effect was observed in the differential γ-ray multiplicities of the two reactions, for deep-inelastic events a larger dipole
γ-ray emission occurs during the more N/Z asymmetric reaction. A theoretical interpretation based on a collective Bremsstrahlung analysis of the reaction dynamics
is presented.
Received: 26 September 2002 / Accepted: 13 November 2002 / Published online: 6 March 2003
RID="a"
ID="a"e-mail: pierroutsakou@na.infn.it
RID="b"
ID="b"Present address: INFN, Laboratori Nazionali di Legnaro, Padova, Italy.
Communicated by C. Signorini 相似文献
17.
Intermediate-energy heavy-ion reactions produce a mid-rapidity region or neck, mostly in the semiperipheral collisions. Brief
theory and experiment surveys are presented. General properties of the mid-rapidity zone are reviewed and discussed in the
framework of reaction dynamics. Hierarchy effect, neutron enrichment, isospin diffusion are all new neck phenomena which are
surveyed. The main neck observables are also examined, mainly in the context of the symmetry term of the nuclear equation
of state. 相似文献
18.
Y.G. Ma 《The European Physical Journal A - Hadrons and Nuclei》1999,6(4):367-371
Zpif's law in the field of linguistics is tested in the nuclear disassembly within the framework of isospin dependent lattice
gas model. It is found that the average cluster charge (or mass) of rank n in the charge (or mass) list shows exactly inversely to its rank, i.e., there exists Zpif's law, at the phase transition
temperature. This novel criterion shall be helpful to search the nuclear liquid gas phase transition experimentally and theoretically.
In addition, the finite size scaling of the effective phase transition temperature at which the Zpif's law appears is studied
for several systems with different mass and the critical exponents of ν and β are tentatively extracted.
Received: 2 June 1999 / Revised version: 8 October 1999 相似文献
19.
W. Nörenberg G. Papp P. Rozmej 《The European Physical Journal A - Hadrons and Nuclei》2002,14(1):43-51
Results on dissipative isoscalar modes of a hot and dilute nuclear droplet are presented. As compared to the adiabatic limit
(part I), realistic dissipation yields a substantial reduction of the growth rates for all unstable modes, while the area
of spinodal instability in the (ϱ,T)-plane remains unchanged. The qualitative features of multifragmentation through spinodal decomposition as obtained in the
adiabatic limit are not significantly affected by dissipation.
Received: 10 January 2002 / Accepted: 10 February 2002 相似文献
20.
P. M. Milazzo G. Vannini M. Bruno N. Colonna M. D’Agostino F. Gramegna G. V. Margagliotti P. F. Mastinu A. Moroni 《The European Physical Journal A - Hadrons and Nuclei》2000,7(3):355-360
The dependence of the nuclear temperatures of highly excited systems, extracted by means of the double ratios of the emitted
isotopes, on the experimental conditions is investigated. Experimental data obtained in the Xe+Cu 30 MeV/nucleon reaction
are used to study the sensitivity of the method and the effects of the energy thresholds on the obtained temperature values.
We find that the temperatures extracted using the He/Li ratios can be strongly influenced by the experimental energy thresholds
which are different for different elements. These distortions depend on the velocity of the emitting system and on the detection
angle and therefore particular care is needed in the choice of the detectors in those experiments in which velocities are
low and angles are large. The use of four isotopes of the same element make negligible such effects.
Received: 6 October 1999 / Accepted: 28 May 2000 相似文献