共查询到20条相似文献,搜索用时 12 毫秒
1.
U. Milkau M. L. Begemann-Blaich E. -M. Eckert G. Imme P. Kreutz A. Kühmichel M. Lattuada U. Lynen C. Mazur W. F. J. Müller J. B. Natowitz C. Ngô J. Pochodzalla G. Raciti M. Ribrag H. Sann W. Trautmann R. Trockel 《Zeitschrift für Physik A Hadrons and Nuclei》1993,346(3):227-236
Inclusive cross sections of intermediate mass fragments from the reaction84Kr+197Au atE/A=35 MeV were measured over the range 8°≦Θ lab≦70° with a low detection threshold. A moving-source parameterization was used to fit the double-differential cross sections. The integrated cross section for fragment production exceeds the total reaction cross section thus indicating a large probability for multi-fragment processes. The deduced large temperature parameters can be explained by assuming emission from a rotating source. From the comparison to reactions with12C and40Ar projectiles at E/A=30 MeV a systematics of inclusive fragment production as a function of the projectile mass is obtained. 相似文献
2.
《Nuclear Physics A》1987,464(1):172-188
Peripheral reactions induced on 92Mo,98Mo, natAg and 197Au targets by 22 MeV per nucleon krypton beam were studied. Fragments observed with velocities close to the beam velocity can be interpreted as coming from a quasi-fragmentation of the projectile. The isotopic distributions measured for the fragments produced with the Kr projectile reflect some influence of the composite system. Thus it seems that projectile fragmentation is not the only mechanism involved in these reactions and that the mean field interaction still plays an important role at this energy. 相似文献
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4.
35MeV/u 40 Ar+197 Au反应中热核的碎裂密度 总被引:1,自引:0,他引:1
许多提取核反应过程中熵产生的方法只适用于高能核反应过程 ,而约化d的产额方法可以用于较低能量的重离子核反应中 .对于 3 5MeV/u40 Ar+ 197Au的核反应过程 ,利用这种方法所得的熵和约化带电粒子多重性提取的熵结果一致 .对于后角热核发射体系 ,实验提取的核温度为 ( 4.7± 1 .2 )MeV ,熵为S/A =2 .5± 0 .5,根据实验提取的熵和核温度可以确定其碎裂密度小于 0 .1 ρ0 相似文献
5.
J. L. Charvet S. Joly M. Morjean Y. Patin Y. Pranal L. Sinopoli J. L. Uzureau R. Billerey B. Chambon A. Chbihi A. Chevarier N. Chevarier D. Drain C. Pastor M. Stern A. Péghaire 《Zeitschrift für Physik A Hadrons and Nuclei》1985,322(4):701-702
We have studied the heavy-ion capture reaction9Be(12C,γ)21 Ne at ECM=3.5–6.6 MeV and Θ = 90. High-energyγ-rav decay to the low-lying states of21Ne was observed, even well below the Coulomb barrier. 相似文献
6.
B. Jäckel A. Rox R. A. Esterlund W. Westmeier M. Knaack P. Patzelt 《Zeitschrift für Physik A Hadrons and Nuclei》1991,339(4):475-487
Mass-yield and angular-distribution data are presented for products from the reaction of 7.1 MeV/
197Au with63Cu. With help from information derived from the latter, the former are classified into components corresponding to quasielastic transfer (580±80 mb), deep-inelastic transfer plus quasifission (1300±130 mb), fusionfission (195 mb), and sequential fission (195±45 mb). The fusion excitation function calculated with the Dynamic Capture model standard parameter set reproduces our deduced fusion-fission cross section well. Moreover, using this cross section as well as additional published data for the same reaction system, we extract ans-wave fusion-barrier shift (extra push) for this system of 35±7 MeV, which is in good agreement with the systematics derived from other fusion-barrier shifts which have been reported in the literature. Lastly, support is found for the Dissipative Diabatic Dynamics model prediction that dynamically-hindered fusion trajectories are reflected into quasielastic channels.Research supported by the Bundesministerium für Forschung und Technologie under contract number 06 MR 553 相似文献
7.
D. Dalili M. Berlanger S. Leray R. Lucas C. Mazur C. Ngô M. Ribrag T. Suomijarvi C. Cerruti S. Chiodelli A. Demeyer D. Guinet A. Genoux Lubin C. Lebrun J. F. Lecolley F. Lefebvres M. Louvel 《Zeitschrift für Physik A Hadrons and Nuclei》1985,322(2):349-350
With laser-atomic-beam-spectroscopy the hyperfinestructure splitting constants A, B and the lifetimes τ of the Mn I levels 3d54s4p z4p3/2,5/2 were determined from the UV intercombination lines 321,7 nm and 322,5 nm. We obtained: A=?821(3)MHz, B=?40(30)MHz, τ=1120(50)nsec for the J=3/2 level and A=?607,8(1,5)MHz, B=+75(15)MHz, τ=970(50)nsec for the J=5/2 level. 相似文献
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Th. Blaich J. V. Kratz R. Schmoll K. Sümmerer G. Wirth 《Zeitschrift für Physik A Hadrons and Nuclei》1996,356(1):49-54
We present radiochemical data on the production of intermediate-mass fragments (IMF, 11≤Z<≈25) in collisions of197Au+197Au at 9, 11, 13 and 15 MeV/u. We demonstrate that the IMFs are produced in two-step reactions: Highly excited heavy nuclei are formed in a binary deep-inelastic reaction, and the IMFs originate from fast mass-asymmetric sequential fission of these primary reaction products. 相似文献
10.
B. Heusch J. P. Coffin P. Engelstein G. Guillaume F. Rami D. Guerreau J. Péter Z. Zheng 《Zeitschrift für Physik A Hadrons and Nuclei》1983,312(1-2):109-111
Fissionlike (FL) phenomena for systems around mass 100 have been shown previously interpretable in terms of dynamical fission. This appears to be dependent on the entrance channel mass asymmetry. We have studied the fissionlike exit channel in the84Kr+24Mg reaction atE(Kr)=5.8 MeV/u. This energy is just above the threshold of fission, so that a clear separation between the Deep Inelastic Component (DIG) and the FL one can be achieved. The bombarding energy corresponds to the same excitation energy in the composite system108Cd (E *=101 MeV) as in the32S (158 MeV) on76Ge reaction we studied earlier and for which fusion-evaporation along with fission-like contributions were measured. The width of the FL distribution confirms the previously observed dependence with the mass asymmetry in the entrance channel which is consistent with the extra push model. 相似文献
11.
Emanuel C. Pollacco Claude Volant Yves Cassagnou Monique Conjeaud Roland Dayras Samuel Harar Robert Legrain Jean -Etienne Sauvestre 《Zeitschrift für Physik A Hadrons and Nuclei》1993,346(1):63-68
Recoil velocities of heavy residues produced in the bombardment of84Kr beams on a232Th target at energies about the Fermi velocity were determined using the method of correlations between fission fragments. The masses of both fragments were also measured. The data show events with high recoil velocity which are produced in incomplete fusion processes. Estimates of the energy transfer are given. Comparisons with incomplete fusion data obtained with other projectiles in the same incident velocity range show an increase of the energy transfer with the mass of the projectile. 相似文献
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13.
The cross sections and angular distributions for fragments emitted in the reaction 620 MeV 86Kr + 197Au have been calculated using the Diffusion Model to describe the approach to equilibrium of the reaction system along the mass-asymmetry coordinate. The calculated quantities are compared with experimental results, and extensions of the theory are discussed. 相似文献
14.
《Physics letters. [Part B]》1987,189(4):388-392
The fragment production in the 84Kr+93Nb reaction at 34.5 MeV/u has been investigated by coincidence measurements. The observed fragment-fragment and fragment-particle correlations can be explained by a binary break-up of a high-velocity source having about 90% of the beam velocity and formed by a deep interaction between the projectile and the target. 相似文献
15.
W. Mittig A. Cunsolo A. Foti J.P. Wieleczko F. Auger B. Berthier J.M. Pascaud J. Quebert E. Plagnol 《Physics letters. [Part B]》1985,154(4):259-262
Heavy residues of collisions of 84Kr + 12C at 35 MeV/amu were measured using time of flight ΔE?E telescopes. An important part of the total cross section leads to events that have all the characteristics of an equilibrated composite system decaying by heavy fragment emission. The experimental yields are well reproduced using a statistical model. 相似文献
16.
B. Heusch H. Freiesleben W. F. W. Schneider B. Kohlmeyer H. Stege F. Pühlhofer 《Zeitschrift für Physik A Hadrons and Nuclei》1985,322(2):309-314
All reaction products in the range from target- and projectile-like to fission-like fragments were measured for the system84Kr+27Al at 5.9 MeV/u beam energy. They are assigned to the various reaction mechanisms on the basis of experimental signatures (energy dissipation, mass and angular distribution). The sum of the measured partial cross sections, including the evaporation residue yield obtained previously, agrees with the total reaction cross section derived from elastic scattering. A small fast-fission component was found, discernible from deep-inelastic reactions by its 1/sin θ angular distribution, and distinguished from compound-nucleus fission by an incomplete mass asymmetry relaxation. 相似文献
17.
S. Leray G. Nebbia C. Gregoire G. La Rana P. Lhenoret C. Mazur C. Ngô M. Ribrag E. Tomasi S. Chiodelli J.L. Charvet C. Lebrun 《Nuclear Physics A》1984,425(2):345-353
We have measured the angular correlation between two fragments emitted in the reactions Ar + Au and Ar + U at 44 MeV/u at GANIL. The aim was to investigate the amount of initial linear momentum transferred from the projectile to a fissioning nucleus. It turned out that this amount is much smaller than can be extrapolated from previous experiments. Furthermore, the probability of forming a fissioning nucleus is very small. 相似文献
18.
A. Yokoyama T. Saito H. Baba K. Hata Y. Nagame S. Ichikawa S. Baba A. Shinohara N. Imanishi 《Zeitschrift für Physik A Hadrons and Nuclei》1989,332(1):61-69
Mechanisms of heavy-ion induced nuclear reactions in mass-asymmetric systems were studied by focusing on the nucleon transfer reaction. Excitation functions and projected mean recoil ranges for the target-like products in37-,16O-,14N-, and12C-induced reactions on197Au were measured by means ofγ-ray spectrometry. The energy range studied was near the Coulomb barrier of the systems with incident energies below 10 MeV/u. Nucleon transfer reactions were discussed by distinguishing the products from quasi-elastic transfer (QET) and those from deep inelastic transfer (DIT). The tendency towards equilibration of theN/Z value and the energy damping, which are the characteristic features of DIT, were found in the production of Au isotopes. Observations are consistent with the generally accepted concept that QET takes place along a trajectory near the Coulomb trajectory. QET was made to be connected with the interaction radius and most of the cross section ratios were reproduced well by an extended tunneling model. 相似文献
19.
《Nuclear Physics A》1997,617(3):385-394
The coincidence measurements between heavy fission fragments and light charged particles with Z ⩽ 2 were carried out for the 40Ar+197Au reaction at 25 MeV/nucleon, to study the properties of hot nuclei in heavy ion induced reactions. The linear momentum transfers (LMTs) were deduced from the folding angle and the time-of-flight difference between two fission fragments of heavy residues. The relationship of the nuclear temperature (slope parameter of the energy spectrum) and the excitation energy was determined independently from the measurement of the kinetic energy spectra in the frames of the emitting sources and from the LMT analysis. Both the temperature and the excitation energy increase with decreasing impact parameter, which suggests that a plateau temperature of 5.5 MeV is reached at an excitation energy of 3.1 MeV/nucleon. The result was also compared with various statistical models that explain the plateau by the multifragmentation process, where the excitation energy is assumed to be stored in compression and expansion effects. 相似文献
20.
G. Bizard R. Brou H. Doubre A. Drouet F. Guilbault F. Hanappe J. M. Harasse J. L. Laville C. Lebrun A. Oubahadou J. P. Patry J. Péter G. Ployart J. C. Steckmeyer B. Tamain 《Zeitschrift für Physik A Hadrons and Nuclei》1986,323(4):459-464
Heavy residues created in the reaction Ar + Ag at 35 MeV/u have been detected at various forward angles. Their velocity spectra (quite different from the corresponding spectra measured at 27 MeV/u) show that these events result both from central and peripheral reactions and that the fusion component has dramatically decreased. Coincident light charged particles spectra have been obtained in a large solid angle forward hodoscope. The analysis of these spectra allows to differentiate peripheral and central collisions. The proton spectra are analysed in terms of emitting sources. There is no need for a participant zone in peripheral reactions. Instead protons are emitted either from the target like or from the projectile like fragments. However projectile sequential emission is not sufficient to explain all the high energy protons. 相似文献