共查询到20条相似文献,搜索用时 31 毫秒
1.
M Dasgupta D J Hinde R D Butt A C Berriman C R Morton J O Newton K Hagino 《Pramana》1999,53(3):513-520
The availability of precisely measured fusion excitation functions have allowed the determination of experimental fusion barrier
distributions. This concept is utilised in 9Be+208Pb reaction, to reliably predict the expected complete fusion cross-sections. However, the measured cross-sections are found
to be only 68% of those predicted. The large cross-sections observed for incomplete fusion products support the interpretation
that this suppression of fusion is caused by 9Be breaking up into charged fragments before reaching the fusion barrier. 相似文献
2.
Excitation function and mean projected recoil ranges of nuclei produced in the12C-induced reactions on51V target were measured by conventional stacked foil and thick-target thick-recoil-catcher technique for bombarding energiesE ≤ 84 MeV for12C ion beam. The measured recoil ranges are converted to momentum transfer. Information on momentum transfer was used to get
clues about some aspects of the interaction such as complete fusion which corresponds to full momentum transfer and incomplete
fusion reaction mechanism. The measured excitation functions are compared with the calculation based on the statistical model
which describes only equilibrium decay of the compound nucleus using the Cascade code and the geometry dependent hybrid model
which describes equilibrium as well as pre-equilibrium decay of the compound nucleus using the Alice/91 code. The measured
excitation functions and average ranges of the radioisotope products of the reactions12C on51V indicate that the three separate reaction mechanisms could be attributable to complete fusion of12C, incomplete fusion of8Be and incomplete fusion of4He respectively with the target. The8Be and4He are the break-up component of12C into8Be +4He. The predictions of the codes, especially the Cascade, generally agree with the measured cross-sections which could be
attributed to complete fusion of12C with the target51V. 相似文献
3.
Excitation function and mean projected recoil ranges of nuclei produced in the7Li and16O induced reactions on51V target were measured by conventional stacked foil and thick-target thick-recoil-catcher technique for bombarding energiesE ≤ 50.0 MeV for7Li ions andE ≃ 60.0-96.0 MeV for the16O ions. The measured recoil ranges are converted to momentum transfer. The momentum transfer information was used to get clues
about some aspects of the interaction such as complete and incomplete fusion reaction mechanism which correspond to full and
reduced momentum transfer respectively. The measured excitation functions are compared with the calculation based on the statistical
model which describes only equilibrium decay of the compound nucleus using the CASCADE code. The comparison of the CASCADE
code with the measured excitation functions for the residue radioisotopes51Cr and54Mn for the7Li +51V system indicates the reaction mechanisms is complete fusion of7Li with the target nucleus51V. Similarly the comparison of the CASCADE code with the measured excitation functions of the residue radioisotopes for the
system16O +51 V indicates that the four reaction mechanisms (i) complete fusion of16O, (ii) incomplete fusion of12C, (iii) incomplete fusion of8Be and (iv) incomplete fusion of4He respectively with the target might be contributing to reaction cross sections. 相似文献
4.
Complete fusion excitation functions for 11,10B+159Tb and 6,7Li+159Tb have been reported at energies around the respective Coulomb barriers. The measurements show significant suppression of
complete fusion cross-sections at energies above the barrier for 10B+159Tb and 6,7Li+159Tb reactions, when compared to those for 11B+159Tb. The comparison shows that the extent of suppression of complete fusion cross-sections is correlated with the α-separation energies of the projectiles. Also, the measured incomplete fusion cross-sections show that the α-particle emanating channel is the favoured incomplete fusion process. Inclusive measurement of the α-particles produced in 6Li+159Tb reaction has been carried out. Preliminary CDCC calculations carried out to estimate the α-yield following 6Li breaking up into α+d fail to explain the measured α-yield. Transfer processes seem to be important contributors. 相似文献
5.
N. Soić D. Cali S. Cherubini E. Costanzo M. Lattuada M. Milin Đ. Miljanić S. Romano C. Spitaleri M. Zadro 《The European Physical Journal A - Hadrons and Nuclei》1998,3(4):303-305
Spectra of coincident charged particles from the reactions induced by a 52 MeV 7Li beam incident on a beryllium target were measured. Strong contributions of the 7Li quasi-free scattering off the α-cluster in 9Be nucleus were observed. This observation supports the conclusions from the study of complete fusion of weakly bound light
nuclei at low energies that the “fragility” of the nuclei makes their fusion less probable.
Received: 1 June 1998 相似文献
6.
F. K. Amanuel B. Zelalem A. K. Chaubey Avinash Agarwal I. A. Rizvi Anjana Maheshwari Tauseef Ahmed 《The European Physical Journal A - Hadrons and Nuclei》2011,47(12):156
In this paper, we present the results of our investigation of reaction dynamics leading to incomplete fusion of heavy ions
at moderate excitation energies, especially the influence of incomplete fusion on complete fusion of 12C -induced reactions at specific energies ≈ 4–7.2M eV/nucleon. Excitation functions of various reaction products populated
via complete and/or incomplete fusions of a 12C projectile with 93Nb, 59Co and 52Cr targets were measured at several specific energies ≈ 4–7.2 MeV/nucleon, using a recoil catcher technique, followed by off-line
γ-ray spectrometry. The measured excitation functions were compared with theoretical values obtained using the PACE4 statistical
model code. For representative non-α-emitting channels in the 12C + 93Nb system, the experimentally measured excitation functions were, in general, found to be in good agreement with the theoretical
predictions. However, for α-emitting channels in the 12C + 93Nb, 12C + 59Co, and 12C + 52Cr systems, the measured excitation functions were higher than the predictions of the theoretical model code, which may be
credited to incomplete fusion reactions at these energies. An attempt was made to estimate the incomplete fusion fraction
for the present systems, which revealed that the fraction was sensitive to the projectile energy and mass asymmetry of the
entrance channel. 相似文献
7.
The thick target yields of the reactions 6Li, 9Be, 10B(d, nγ) for specific final nucleus γ-rays have been measured between deuteron bombarding energies of 48 and 170 keV. The measured thick target yields are used, together with recently published values of the stopping power of low-energy deuterons in matter, to infer the total reaction cross sections for the production of the specific γ-rays between deuteron energies of 65 and 160 keV. The cross sections are compared to appropriate Coulomb barrier penetration probabilities and the astrophysical functions S(E) are deduced. 相似文献
8.
A Szanto de Toledo N Carlin N Added E M Szanto M G Munhoz J Takahashi A Suaide M M de Moura 《Pramana》1999,53(3):483-483
Considerable interest has been devoted to fusion reactions between light heavy ions specially between weakly bound ones, due
to the anomalous decrease of the fusion cross sections when compared to the total reaction cross section in the energy region
around the barrier [1–4].
While the exact nature of the process responsible for the fusion cross section limitation at barrier energies is still unclear,
this study shows an inhibition of the yield as the system mass decreases, resulting from the progressive increase of the barrier
height and decrease of the effective barrier radius [3]. Furthermore, extensive efforts have been made recently in the study
of energy-damped binary yields from light heavy-ion collisions [2,4]. Based on the substantial amount of data accumulated
so far, it is now generally accepted and supported by the transition state model [4], that the observed yields arise mostly
from a fusion-fission process. Data on complete fusion, fusion-fission and ‘elastic fission’ for the 9Be, 10,11B+10,11B; 16,17,18O + 10,11B; 19F+12C; 6,7Li+9Be, 12C reactions among others, are presented. For the loosely bound nuclei it was found that the severe fusion cross section limitation
is due to a low survival probability of the weakly bound nuclei until the instant of the collision [1]. 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.
M. Mazzocco C. Signorini M. Romoli R. Bonetti A. De Francesco A. De Rosa M. Di Pietro L. Fortunato T. Glodariu A. Guglielmetti G. Inglima T. Ishikawa H. Ishiyama R. Kanungo N. Khai S. Jeong M. La Commara B. Martin H. Miyatake T. Motobayashi T. Nomura D. Pierroutsakou M. Sandoli F. Soramel L. Stroe I. Sugai M. H. Tanaka E. Vardaci Y. Watanabe A. Yoshida K. Yoshida 《The European physical journal. Special topics》2007,150(1):37-40
The elastic scattering process for 11Be ions impinging on
a 209Bi target was studied in the energy range around the
Coulomb barrier. The angular distributions of the 11Be scattered
particles were analyzed within the optical model framework in order
to evaluate the reaction cross section, which turned out to be much larger
than the fusion one, especially in the sub-barrier region. The comparison
with the system 9Be + 209Bi showed that the reaction cross section
is larger for the reaction 11Be + 209Bi in the energy range around
the Coulomb barrier, while they are rather similar at higher bombarding energies.
This result suggests that direct processes related to the 11Be
halo structure and lower binding energy are more relevant
at near-barrier energies. 相似文献
11.
P. R. S. Gomes I. Padron O. A. Capurro J. O. Fernández Niello G. V. Martí A. J. Pacheco A. Arazi J. Lubian E. Crema 《X射线光谱测定》2008,37(5):512-516
We describe how the method of detection of delayed K x‐rays produced by the electron capture decay of the residual nuclei can be a powerful tool in the investigation of the effect of the breakup process on the complete fusion (CF) cross‐section of weakly bound nuclei at energies close to the Coulomb barrier. This is presently one of the most interesting subjects under investigation in the field of low‐energy nuclear reactions, and the difficult experimental task of separating CF from the incomplete fusion (ICF) of one of the breakup fragments can be achieved by the x‐ray spectrometry method. We present results for the fusion of the 9Be + 144Sm system. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
12.
《Nuclear Physics A》1995,588(1):c109-c112
Fusion cross sections of 11Be, 10Be and 9Be have been measured on 209Bi target at 30–70 MeV. Due to the neutron halo effect of 11Be, a large enhancement or suppression of the fusion cross section around the Coulomb barrier was theoretically predicted. Comparing the excitation function of 11Be with 10Be at near the Coulomb barrier region, no significant difference has been observed. 相似文献
13.
The 16O + 9Be reactions have been studied from Ec.m. = 2.0 MeV to 5.1 MeV, an energy near the top of the Coulomb barrier. The cross section for the neutron transfer reaction 9Be(16O,17O1 (0.87 MeV))8Be has been measured over this range by detecting the prompt 0.87 MeV γ-rays. The total fusion cross section has been determined from Ec.m. = 2.8 to 5.1 MeV by observing individual γ-ray transitions in the evaporation residues with a Ge(Li) detector, and then summing the separate yields. Direct processes are found to dominate the reaction yield below Ec.m. = 4 MeV. A comparison of the energy dependence of the fusion cross section for this reaction and the 12C + 13C reaction, which proceeds via the formation of the same compound nucleus, 25Mg, reveals differences at sub-barrier energies. Optical model and incoming-wave boundary condition calculations are presented. Data have also been obtained for the near optimum Q-value neutron-transfer reactions 9Be(12C, 13C1)8Be and 9Be(19F, 20F)8Be, and these are discussed in terms of a simple model of sub-barrier direct reactions. 相似文献
14.
D SINGH RAHBAR ALI M AFZAL ANSARI B S TOMAR M H RASHID R GUIN S K DAS R KUMAR R P SINGH S MURALITHAR R K BHOWMIK 《Pramana》2014,82(4):683-696
Three different types of experiments have been performed to explore the complete and incomplete fusion dynamics in heavy-ion collisions. In this respect, first experiment for the measurement of excitation functions of the evaporation residues produced in the 20Ne + 165Ho system at projectile energy ranges ≈2–8 MeV /nucleon has been done. Measured cumulative and direct cross-sections have been compared with the theoretical model code PACE-2, which takes into account only the complete fusion process. It has been observed that, incomplete fusion fraction is sensitively dependent on projectile energy and mass asymmetry between the projectile and the target systems. Second experiment for measuring the forward recoil range distributions of the evaporation residues produced in the 20Ne + 165Ho system at projectile energy ≈8 MeV /nucleon has been done. It has been observed that, some evaporation residues have shown additional peaks in the measured forwardrecoil range distributions at cumulative thicknesses relatively smaller than the expected range of the residues produced via complete fusion. The results indicate the occurrence of incomplete fusion involving the breakup of 20Ne into 4He + 16O and /or 8Be + 12C followed by one of the fragments with target nucleus 165Ho. Third experiment for the measurement of spin distribution of the evaporation residues produced in the 16O + 124Sn system at projectile energy ≈6 MeV /nucleon, showed that the residues produced as incomplete fusion products associated with fast α and 2 α-emission channels observed in the forward cone, are found to be distinctly different from those of the residues produced as complete fusion products. The spin distribution of the evaporation residues also inferred that in incomplete fusion reaction channels input angular momentum (J 0) increases with fusion incompleteness when compared to complete fusion reaction channels. Present observation clearly shows that the production of fast forward α-particles arises from relatively larger angular momentum in the entrance channel leading to peripheral collision. 相似文献
15.
P.R.S. Gomes J. Lubian B. Paes V.N. Garcia D.S. Monteiro I. Padrn J.M. Figueira A. Arazi O.A. Capurro L. Fimiani A.E. Negri G.V. Martí J.O. Fernndez Niello A. Gmez-Camacho L.F. Canto 《Nuclear Physics A》2009,828(3-4):233-252
Fusion, breakup and scattering for the 9Be + 144Sm system at near barrier energies are investigated by different approaches. We show that at energies above the barrier there is a small complete fusion suppression when compared with predictions from a double folding potential and with a similar tightly bound system. At sub-barrier energies there is no significant deviation from the predictions using coupled channel calculations that do not include the breakup channel. The energy dependence of the optical potential does not show the usual threshold anomaly found in tightly bound systems. From a simultaneous analysis of fusion and scattering data we estimate the distance where breakup starts to occur. 相似文献
16.
S. Verma J. J. Das A. Jhingan K. Kalita S. Barua K. S. Golda N. Madhavan P. Sugathan S. Nath T. Varughese J. Gehlot S. Mandal S. Ranjit P. K. Sahu B. John B. K. Nayak A. Saxena S. K. Datta R. Singh 《The European physical journal. Special topics》2007,150(1):75-78
Elastic scattering angular distributions have been measured for 7Be + 9Be system at Elab = 17, 19 and 21 MeV in the angular range θcm=26○–58°, and for 7Li + 9Be system at Elab= 15.75, 24 and 30 MeV.
An optical model (OM) analysis of these data have been carried out.
For the 7Li + 9Be system fusion cross sections were obtained at Elab = 15.75, 24 and 30 MeV by measuring the α-evaporation spectra from the compound nucleus at backward angles. The measured
α-evaporation spectra were reproduced by the statistical model calculations and fusion cross sections were extracted therefrom.
The ratios of the experimental fusion cross sections to the total reaction cross sections (obtained form OM analysis) were
found to be rather small. This result suggests that break-up process has a strong influence on fusion process leading to a
reduction in fusion cross section. 相似文献
17.
E. Ungricht D. Balzer M. Hugi J. Lang R. Müller L. Jarczyk B. Kamys A. Strzalkowski 《Nuclear Physics A》1979,313(3):376-384
The elastic scattering of 9Be on the target nuclei 9Be, 12C, 13C and 16O was measured at projectile energies of 14, 20 and 26 MeV. All angular distributions show a diffraction-like structure. In addition, excitation curves were measured for the scattering of 9Be on 9Be at three different angles in the energy range of 9–22 MeV. An optical potential having parameters independent of mass number and energy and reproducing all the measured angular distributions in the forward angular region was found and compared with that for the scattering of 9Be on medium and heavy nuclei. 相似文献
18.
Theoretical simulation of residual velocity distributions at various mass windows for complete and incomplete fusion reactions have been done for the system40Ar+24Mg at the incident energies of 1100, 800 and 600 MeV. The comparison of the residual velocity distributions enables us to have a qualitative understanding about the relative contributions of the complete and incomplete fusion processes in intermediate energy heavy ion reaction. 相似文献
19.
In this study, the production yield for the reaction 176Yb(9Be, α3n)178Hf was explored using the FN tandem injected superconducting LINAC at SUNY at Stony Brook at a 9Be energy of 65 MeV. By comparing the experimental yield of 178Hf ground state γ rays with those of 180W as a function of energy, the cross section for production of the incomplete fusion γ rays in 178Hf was evaluated. Coincidence measurements were made to get information about the population strength of the high spin states
in 178Hf. From these measurements, the maximum cross section for the reaction 176Yb(9Be, α3n)178m2Hf is estimated to be no larger than 5 mb.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
20.
《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