共查询到20条相似文献,搜索用时 984 毫秒
1.
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
2.
J. F. Liang D. Shapira C. J. Gross R. L. Varner H. Amro J. R. Beene J. D. Bierman A. L. Caraley A. Galindo-Uribarri J. Gomez del Campo P. A. Hausladen K. L. Jones J. J. Kolata Y. Larochelle W. Loveland P. E. Mueller D. Peterson D. C. Radford D. W. Stracener 《The European physical journal. Special topics》2007,150(1):35-36
Evaporation residue and fission cross sections of radioactive
132Sn on 64Ni were measured. Statistical model calculations
using parameters simultaneously fitting stable Sn+64Ni data
reproduce the 132Sn induced reaction very well. A large
sub-barrier fusion
enhancement was observed. The enhancement can be accounted for by
coupled-channels calculations including inelastic excitation of the
projectile and target, and neutron transfer. 相似文献
3.
R. A. Gherghescu W. Greiner S. Hofmann 《The European Physical Journal A - Hadrons and Nuclei》2006,27(1):23-32
A specialized macroscopic-microscopic method is applied to calculate binary configuration deformation energy for fusion processes.
The deformed two-center shell model is utilized to obtain the transition of the two independent level schemes for target and
projectile, going through overlapping configuration up to the final compound nucleus. The macroscopic part is obtained with
the usual Yuakawa-plus-exponential method applied to fusion-like configuration. The tensor of inertia is obtained within the
Werner-Wheeler approach and dynamics is treated using the multidimensional WKB penetrability method. Calculations are applied
to the sub-barrier synthesis of 294,290,286,280118 isotopes. 相似文献
4.
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
5.
We obtain a closed-form expression for the distribution of fusion barriers for vibrational nuclei using a generalization of
Dasso, Landowne, and Winther's model, which represents the nuclear surface vibrations as a number of harmonic oscillators,
and allows the excitation of an arbitrary number of phonons in the target and/or projectile. We find that this expression
is in reasonable agreement with the average trends of the empirical distributions for the fusion of 16O with 92Zr, 144Sm and 208Pb, but fails to reproduce the double peaking of the distribution for the 144Sm target. Only when we restrict the number of excited phonons to a limited number, we are able to reproduce such discrete
structures. We show that limiting the number of coupled channels, particularly in the case of strong coupling, increases the
spacings between the channel eigenvalues that determine the positions of the peaks of the barrier distribution and modifies
their heights.
Received: 6 March 2000 / Accepted: 31 January 2001 相似文献
6.
C. Signorini 《The European Physical Journal A - Hadrons and Nuclei》2002,13(1-2):129-133
The experimental data relative to the interaction for the systems 9, 10, 11Be + 209Bi at the Coulomb barrier are critically discussed and compared also with present theories. The break-up (BU) of the two loosely
bound projectiles, 9, 11Be, seems to influence the fusion process by “hindering” the fusion cross-sections; but, contrary to expectations, the 11Be halo structure has no influence, since no “enhancement” is evident from the existing data. Attempt to describe simultaneously
all the 9Be + 209Bi system data: fusion, elastic scattering and BU, within a coupled-channel (CC) approach is only partly successful. It is
important, from a theoretical viewpoint, to include in the CC formalism as well as possible the BU process both to continuum
states as well as to unbound resonances. More accurate and well-focused experiments are also necessary to pin down this problem.
Received: 1 May 2001 / Accepted: 4 December 2001 相似文献
7.
L.M. Pant R.K. Choudhury A. Saxena D.C. Biswas 《The European Physical Journal A - Hadrons and Nuclei》2001,11(1):47-58
Fission fragment mass and energy distributions and their correlations have been measured for the 16O and 19F + 209Bi reactions over a wide range of excitation energies ( E
* = 30-50 MeV). It is observed that in the case of 16O + 209Bi reaction, the average total fragment kinetic energy, <TKE> is nearly independent of the bombarding energy. However, in the case of 19F + 209Bi reaction, the average total kinetic energy of the fission fragments shows a peaking behaviour near the barrier. The variation
in <TKE> at near barrier energies in the 19F + 209Bi system seems to be correlated with corresponding strong variation in the variance of the fragment mass distribution. The
present results may imply certain dynamical effects leading to compact scission configurations in the fission of 19F + 209Bi system at near barrier bombarding energies.
Received: 9 April 2001 / Accepted: 26 May 2001 相似文献
8.
S. Mukherjee A. Sharma S. Sodaye B.S. Tomar A. Goswami S.B. Manohar 《The European Physical Journal A - Hadrons and Nuclei》2001,12(2):199-205
Incomplete fusion reactions were investigated by measuring the excitation functions of nine evaporation residues in 16O + 51V reaction in the beam energy 4-6 MeV/amu, using the well-known recoil catcher technique and gamma-ray spectrometry. The experimental
data were compared with that obtained from Monte Carlo simulation calculations using the PACE2 code. The results indicate
the presence of incomplete fusion process in the production of two alpha emission products. This was further confirmed by
the measurement of recoil range distribution of these isotopes at 96 MeV beam energy. Calculations of the average angular
momentum associated with these products revealed the peripheral nature of these ICF reactions.
Received: 20 June 2001 / Accepted: 11 September 2001 相似文献
9.
Partial-fusion cross-sections for the systems 6Li + 208Pb, 9Be + 209Bi have been determined. The effect of breakup on fusion for weakly bound projectiles 6Li and 9Be incident on 208Pb or 209Bi targets has been discussed comparing experimental fusion cross-section excitation functions to those evaluated with a semi-classical
approach. It is shown that complete fusion of a weakly bound projectile with heavy target is reduced, whereas the breakup
process has very little influence on the total-fusion cross-section for some of the studied systems at energies above the
Coulomb barrier. 相似文献
10.
11.
《Nuclear Physics A》1995,588(1):c85-c89
The sub-barrier fusion of halo nuclei such as 11Be and 11Li with heavy target nuclei is discussed. The couplings to the soft dipole mode as well as to the break-up channels are taken into account. At barrier energies, the fusion cross section was found to be more than one order of magnitude smaller than that corresponding to the uncoupled problem. At sub-barrier energies, it was shown to be larger. 相似文献
12.
J.J. Kolata 《The European Physical Journal A - Hadrons and Nuclei》2002,13(1-2):117-121
The fusion of 6He with a 209Bi target displays a large enhancement at energies near to and below the Coulomb barrier. Recently, a 4He group of remarkable intensity, which dominates the total reaction cross-section, has also been observed in the near-barrier
interaction of the same system. It is argued that this transfer/breakup channel acts as a doorway state to fusion.
Received: 1 May 2001 / Accepted: 4 December 2001 相似文献
13.
Static versus energy-dependent nucleus–nucleus potential for description of sub-barrier fusion dynamics of _8~(16)O+_(50)~(112,116,120)Sn reactions 下载免费PDF全文
Manjeet Singh Gautam 《中国物理C(英文版)》2015,39(11):114102-114102
The static and energy-dependent nucleus–nucleus potentials are simultaneously used along with the Wong formula for exploration of fusion dynamics of168O+112,116,12050 Sn reactions. The role of internal structure degrees of freedom of colliding pairs, such as inelastic surface vibrations, are examined within the context of coupled channel calculations performed using the code CCFULL. Theoretical calculations based on the static Woods–Saxon potential along with the one-dimensional Wong formula fail to address the fusion data of168O+112,116,12050 Sn reactions.Such discrepancies can be removed if one uses couplings to internal structure degrees of freedom of colliding nuclei.However, the energy-dependent Woods–Saxon potential model(EDWSP model) accurately describes the sub-barrier fusion enhancement of168O+112,116,12050 Sn reactions. Therefore, in sub-barrier fusion dynamics, energy dependence in the nucleus–nucleus potential governs barrier modification effects in a closely similar way to that of the coupled channel approach. 相似文献
14.
A.M. Samant S. Kailas A. Chatterjee A. Shrivastava A. Navin P. Singh 《The European Physical Journal A - Hadrons and Nuclei》2000,7(1):59-64
The fission fragment angular distributions have been measured for the system 19F +209Bi over a range of bombarding energies from 88.0 MeV to 125.6 MeV. The measured fission fragment anisotropies are in agreement
with the saddle point statistical model calculations in the above energy range. Combining these data with those available
for 11B, 12C, 14N, 16O and 18O +209Bi, 208Pb systems, it is concluded that the spherical target plus projectile systems behave “normal” from near- to above – barrier
energies. This observation is in contrast to the “anomalous” anisotropies exhibited by the deformed actinide target – projectile
systems at near – barrier energies.
Received: 5 May 1999 / Revised version: 25 July 1999 相似文献
15.
D.J. Hinde A.C. Berriman R.D. Butt M. Dasgupta C.R. Morton A. Mukherjee J.O. Newton 《The European Physical Journal A - Hadrons and Nuclei》2002,13(1-2):149-154
In the fusion of heavy nuclei, there is a distribution of fusion barrier energies resulting from coupling between intrinsic
motion and internal degrees of freedom. Precise experimental measurements of excitation functions have allowed the extraction
of the distributions by taking the second derivative using a point-difference method. In the case of statically deformed nuclei,
experimental data shows that the different fusion barrier energies correspond to different physical configurations of the
colliding nuclei, the latter affecting the subsequent dynamical trajectories over the potential energy surface, influencing
the ultimate reaction products, as for example in quasi-fission. The fusion barrier distribution is also valuable in understanding
the fusion of weakly bound nuclei, enabling a reliable prediction of the expected fusion cross-sections, and thus the determination
of fusion suppression factors at above-barrier energies.
Received: 1 May 2001 / Accepted: 4 December 2001 相似文献
16.
Production cross sections for the heaviest nuclei in complete
fusion reactions induced by heavy ions
R. N. Sagaidak 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,45(1):59-65
Production of the heaviest nuclei in complete fusion reactions
induced by heavy ions has been considered in a systematic way in the framework
of the conventional barrier passing model coupled with the statistical model.
Available data on excitation functions for fission and production of
evaporation residues (ER) in very asymmetric combinations induced by ions
lighter than Ne on actinide target nuclei are described rather well in the
framework of these models. The data allow one to adjust model parameters and to
reveal the quasi-fission effect caused by the interaction with deformed target
nuclei, which is manifested in the suppression of the ER production at
sub-barrier energies. For reactions induced by Mg and heavier projectiles,
quasi-fission is starting to suppress fusion (ER production) at energies above
the Coulomb barrier. One has to introduce empirically the quantity of the
fusion probability Pfus to reproduce the ER excitation functions
in the framework of the conventional approach. The exponential dependence of
Pfus on the combined fissility parameter (a similar parameter
that was introduced for the extra-push energy scaling) was found in search for
scaling for the Pfus values resulting from the data analysis. 相似文献
17.
P. David J. Bisplinghoff M. Blann T. Mayer-Kuckuk A. Mignerey 《Nuclear Physics A》1977,287(1):179-188
Evaporation residue excitation functions have been measured for 35Cl ions up to 170 MeV (lab) on targets of 112, 120Sn and 141Pr. These values are combined with previously reported fission excitation functions to give fusion excitation functions. Classical analysis of these results yield fusion barriers and fusion radii. Earlier results are confirmed: as the target atomic number increases the required density penetration at the fusion barrier increases. The percentage of the reaction cross section undergoing fusion monotonically decreases as the targets go from 27Al to 141Pr. The nuclear contribution to the fusion barrier deduced from these measurements is compared with several model predictions and is found to be in satisfactory agreement with the models due to Bass and Krappe and Nix. 相似文献
18.
A. M. Stefanini M. Trotta B. R. Behera L. Corradi E. Fioretto A. Gadea A. Latina S. Szilner Y. W. Wu S. Beghini G. Montagnoli F. Scarlassara A. Yu. Chizhov I. M. Itkis N. A. Kondratiev I. V. Pokrovskiy R. N. Sagaidak G. N. Kniajeva E. M. Kozulin V. M. Voskressensky S. Courtin F. Haas N. Rowley 《The European Physical Journal A - Hadrons and Nuclei》2005,23(3):473-480
Measurements of fusion-evaporation cross-sections for the system 48Ca + 154Sm have been performed in the sub- and near-barrier energy range. Barrier-passing cross-sections have been obtained by adding recently measured capture-fission cross-sections at the same energies, and the barrier distribution for capture has been extracted. The data have been analyzed within a coupled-channel model, and a large subbarrier cross-section enhancement is observed, due to the ground-state prolate deformation of 154Sm. The 48Ca + 154Sm capture cross-sections are compared to existing data on 16O + 186W fusion, leading to the same CN, where a few higher-energy points have also been measured. The evaporation residue cross-sections for the two systems above the barrier indicate that complete fusion is inhibited for 48Ca + 154Sm by 40% in that energy region, with respect to 16O + 186W. 相似文献
19.
Yu. E. Penionzhkevich R. A. Astabatyan N. A. Demekhina G. G. Gulbekian R. Kalpakchieva A. A. Kulko S. M. Lukyanov E. R. Markaryan V. A. Maslov Yu. A. Muzychka Yu. Ts. Oganessian R. V. Revenko N. K. Skobelev Yu. G. Sobolev D.A.Testov T. Zholdybaev 《The European Physical Journal A - Hadrons and Nuclei》2007,31(2):185-194
Excitation functions for evaporation residues in the reactions 197Au(6He, xn)203-xnTl, x = 2-7, and 206Pb(6He, 2n)210Po, as well as for neutron transfer reactions for the production of 196Au and 198Au in the interaction of 6He with 197Au were measured. The 6He beam was obtained from the accelerator complex for radioactive beams DRIBs (JINR). The maximum energy of the beam was about
10AMeV and the intensity reached 2×107pps. The stacked-foil activation technique was used directly in the beam extracted from the cyclotron or in the focal plane
of the magnetic spectrometer MSP-144. The identification of the reaction products was done by their radioactive γ- or α-decay.
The fusion reaction with the evaporation of two neutrons was characterized by an increase in the cross-section compared to
statistical model calculations. The analysis of the data in the framework of the statistical model for the decay of excited
nuclei, which took into account the sequential fusion of 6He has shown good agreement between the experimental and the calculated values of the cross-sections in the case of sub-Coulomb-barrier
fusion in the 206Pb + 6He reaction. An unusually large cross-section was observed below the Coulomb barrier for the production of 198Au in the interaction of 6He with 197Au. Possible mechanisms of formation and decay of transfer reaction products are discussed. 相似文献
20.
C. Signorini Z.H. Liu A. Yoshida T. Fukuda Z.C. Li K.E.G. Löbner L. Müller Y.H. Pu K. Rudolph F. Soramel C. Zotti J.L. Sida 《The European Physical Journal A - Hadrons and Nuclei》1998,2(3):227-231
The 9Be +209Bi fusion cross sections were measured in the range 37.5 MeV ≤ E
lab
≤ 45.0 MeV at the Munich Tandem via the observation of ground state α-decay of the evaporation residues. Fusion cross sections
of 209Bi with the “halo”11Be unstable projectile in the region around the Coulomb barrier were deduced from an experiment done with the same technique
at the RIKEN Ring Cyclotron. Above the Coulomb barrier the 11Be cross sections are larger than the 9Be ones in agreement with theoretical predictions based on the larger 11Be halo radius. Also below the barrier these theories foresee the same behavior in disagreement with the experimental results,
since the two cross sections are rather similar.
Received: 2 April 1998 相似文献