共查询到20条相似文献,搜索用时 78 毫秒
1.
B. Gatty D. Guerreau M. Lefort X. Tarrago J. Galin B. Cauvin J. Girard H. Nifenecker 《Nuclear Physics A》1975,253(2):511-532
Masses and charges of all the nuclei with 5 ≦ Z ≦ 20 produced in the reaction 40Ar + 58Ni have been identified using combined ΔE · E and time-of-flight techniques. Energy spectra, angular distributions and cross sections have been measured. The formation of an intermediate composite system, in which charge equilibrium is achieved, is discussed. Also, the transition between the quasi-elastic and the deep inelastic process is studied. The angular distribution behaviour is shown to be related to the interaction time. The total cross section of the deep inelastic process has been found to be 700 mb and is compared to the evaporation residue cross section. 相似文献
2.
H. Morgenstern W. Bohne S. Proschitzki 《Zeitschrift für Physik A Hadrons and Nuclei》1992,344(3):259-267
We report on measurements of fusion-fission fragments and evaporation residues from the reaction58Ni +27Al at 835 MeV incident energy leading to compound nucleiA ≦ 85 with high excitation energies. In the case of fission the mass dependence of the velocity widths of separated fragments indicate that the evaporation of light particles predominantly occurs from the composite nucleus prior to scission. The fraction evaporated from the fully separated fragments after scission can be estimated to approximately 20%. 相似文献
3.
R. Babinet B. Cauvin J. Girard H. Nifenecker B. Gatty D. Guerreau M. Lefort X. Tarrago 《Nuclear Physics A》1978,296(1):160-176
The binary character of the deep inelastic collisions observed in the reaction 58Ni + 40Ar at 280 MeV has been investigated. Two major fragments were detected in coincidence. The light fragment was identified both in mass (by the time of flight technique) and charge (using a ΔE-E telescope). Within the experimental uncertainties, the hypothesis of a binary process has been verified. More than 80% of the events correspond to a reaction mechanism where, apart from light particles, only two major fragments are observed in the exit channel. The deviation from an exactly binary process leads to an indirect measurement of the number of particles evaporated by the excited fragments. The total mass of the particles emitted by the light fragment alone is deduced. The results are suggestive of equal temperature for both light and heavy fragments. Finally, the total number of particles evaporated is estimated. The emission of α-particles is invoked in order to consistently explain the data. 相似文献
4.
R. Babinet B. Cauvin J. Girard J. M. Alexander T. H. Chiang J. Galin B. Gatty D. Guerreau X. Tarrago 《Zeitschrift für Physik A Hadrons and Nuclei》1980,295(2):153-167
Protons andα-particles emitted in coincidence with a deep inelastic fragment produced in the reaction40Ar (280 MeV)+58Ni have been measured. From a detailed study of their in-plane angular distribution, it is shown that the bulk of the light charged particle emission can be attributed to a secondary evaporation process by the two primary deep inelastic fragments. A lowest estimate of the fragment spin (assuming total alignment perpendicular to the reaction plane) is obtained from the anisotropy of the out-of-plane angular distribution of theα-particles. For very asymmetric splitting, the heavy fragment spin estimate as obtained from theα-anisotropy measurement is consistent with the observed proton toα-particle multiplicity ratio. The results are in agreement with the hypothesis of a sticking configuration between two deformed nuclei. 相似文献
5.
W. Kühn R. Albrecht H. Damjantschitsch H. Ho R. M. Ronningen J. Slemmer J. P. Wurm I. Rode F. Scheibling 《Zeitschrift für Physik A Hadrons and Nuclei》1980,298(2):95-101
In and out-of-plane angular correlations between light particles and projectile-like fragments from deeply inelastic collisions of 400 MeV40Ar+93Nb were measured. At backward angles, the equilibrium emission of a particles and protons from the target-like fragment was identified. By analysing the out-of-plane angular correlations in the framework of a semi-classical statistical model, an average spin of 30±2? and an average alignment ofP zz =0.80±0.15 for the target-like fragment were deduced. 相似文献
6.
7.
Inclusive proton spectra and proton-proton correlations have been measured from α + 58Ni and α + 197Au reactions at energies Eα = 100 MeV and 172 MeV. The inclusive spectra are compared to results of a simple model assuming local equilibration of the energy transferred to the target nucleons. This model describes the energy and angular dependence sufficiently well at angles ? 40°. Due to finite number effects, it also explains the occurrence of differences between in-plane to out-of-plane pp correlations. In addition, the measured coincidences indicate contributions from quasifree pp scattering. 相似文献
8.
D. Brill P. Beckerle C. Bormann E. Schwab Y. Shin R. Stock H. Ströbele P. Baltes C. Müntz H. Oeschler C. Sturm A. Wagner R. Barth M. Cieślak M. Dębowski E. Grosse P. Koczoń M. Mang D. Miśkowiec R. Schicker P. Senger B. Kohlmeyer F. Pühlhofer J. Speer K. Völkel W. Waluś 《Zeitschrift für Physik A Hadrons and Nuclei》1996,355(1):61-68
Midrapidity protons from209Bi+209Bi collisions were measured with the Kaon Spectrometer at SIS at incident energies of E Lab /A=400, 700 and 1000 MeV. Additionally, light fragments were analysed at 400 MeV. We have investigated the azimuthal emission pattern of the particles relative to the reaction plane as function of transverse momentum, bombarding energy and impact parameter. We observe an enhanced emission of particles perpendicular to the reaction plane at all bombarding energies. The ratio of the number of particles emitted out-of-plane/in-plane increases strongly with the particles transverse momentum. The anisotropy decreases with increasing beam energy. Composite particles show a much stronger effect than protons. 相似文献
9.
《Nuclear Physics A》1997,622(4):573-592
We present new experimental results concerning the azimuthal distributions of proton-likes, light and intermediate mass fragments at midrapidity for Au(100–800 A MeV) +Au collisions measured with the FOPI phase-I detector at GSI in Darmstadt. The azimuthal distributions are investigated as a function of the collision centrality, the incident energy, the fragment charge and transverse momentum. The azimuthal anisotropy is maximum for impact parameters around 7 fm. Intermediate mass fragments present a stronger out-of-plane emission signal than light fragments and a saturation is reached for Z ⩾ 4. The azimuthal anisotropy increases with the fragment transverse momentum and decreases as the incident energy increases. The azimuthal anisotropy of Z = 2 particles investigated as a function of the scaled fragment transverse momentum follows an universal curve for bombarding energies between 250–800 A MeV. A signature for a transition from in-plane to out-of-plane emission is evidenced at the lowest beam energies. 相似文献
10.
Toshiaki Izumoto 《Nuclear Physics A》1978,301(3):448-462
We have studied the isospin non-conserving 12C(d, α)10B(1.74 MeV, 0+, T= 1) reaction at several incident energies of 9 ≦ Ed ≦ 16 MeV in terms of a coupled-channels method. The reaction processes involved in the present analysis are the successive single-nucleon pick-up processes as well as the inelastic scattering of deuterons from 12C. It is assumed that the isospin violation should occur in the intermediate mirror cluster states of 3He + 11B and t + 11C, due to the Coulomb interaction. The calculation reproduces fairly well the observed features of the reaction, i.e. the decreasing cross section with increasing incident energy, and the variation of the angular distribution. We also note that the calculation shows the energy-dependent localization of isospin violation in the angular momentum space, i.e. a specifically narrow localization at the lower incident energies studied and its broadening at the higher energies. This fact is associated with the variation of the angular distribution from a forward-backward symmetry at the lower incident energies to a forward peak at the higher energies. 相似文献
11.
12.
Mass distributions of evaporation residues from the fusion of 63Cu + 65Cu have been measured at seven excitation energies from 55 to 105 MeV in a single irradiation experiment. They are interpreted as a mixture of residues produced by single nucleon evaporation cascades and cascades including α-particle evaporation. Compound nuclei with an average excitation energy of 55 MeV () are still found to have a probability as high as 0.3 % for decaying by emission of a single nucleon. The low-energy behaviour of the excitation function can be interpreted as a fusion barrier effect. The parameters of this barrier are determined. The evaporation residue cross section at higher energies is shown to be limited by the fission of the compound nucleus. 相似文献
13.
W. von Oertzen B. Gebauer G. Efimov V. Zherebchevsky Tz. Kokalova S. Thummerer Ch. Schulz H. G. Bohlen D. Kamanin C. Beck D. Curien P. Papka M. Rousseau G. Royer G. de Angelis 《The European Physical Journal A - Hadrons and Nuclei》2008,36(3):279-288
Coincidences between two heavy fragments have been measured from the fission of 56Ni compound nuclei formed in the 32S + 24Mg reaction at E
lab( ^32S ) = 165.4 MeV. A unique experimental set-up consisting of two large-area position-sensitive (x, y) gas detector telescopes has been used allowing the complete determination of the observed fragments and their momentum vectors.
In addition to binary fission events with subsequent particle evaporation, narrow out-of-plane correlations are observed for
two fragments emitted in purely binary events and in events with a missing charge consisting of 2α - and 3α -particles (12C). These events are interpreted as ternary cluster decay from 56Ni nuclei at high angular momenta through hyper-deformed shapes. 相似文献
14.
D.L. Hillis J.D. Garrett O. Christensen B. Fernandez G.B. Hagemann B. Herskind B.B. Back F. Folkmann 《Nuclear Physics A》1979,325(1):216-268
The moments of the γ-ray multiplicity distributions as a function of evaporation residue and of Eγ have been determined from γ-multiplicity measurements for the 116, 120, 122, 124Sn(40Ar, xn) reactions at 161 ≦ E(Ar) ≦ 236 MeV and for the 76Ge(86Kr, xn) reaction at 314 ≦ E(Kr) ≦ 376 MeV. Even at the highest incident energies where lgr ≈ 120 units, it is not possible to populate nuclei with l > 65 units, the limiting l predicted for a rotating liquid drop. For the lowest incident energies these data are in agreement with the decay of a compound system. At the highest incident energy, however, significant deviations are observed from the expected decay of an equilibrated system. Such deviations are indicative of pre-equilibrium particle decay. Statistical calculations utilizing the code GROG12 are used to substantiate these conclusions. No evidence for a lower l-cut in the population of the compound system is observed; however, these data would not be sensitive to an lcut ? 10 units. The moments of inertia extracted from the edge of the “collective E2 bump” in the 〈Mγ〉 versus Eγ data are in agreement with those predicted for a rotating liquid drop. The average multiplicity of the noncompound processes is estimated to be 8–11 for lgr ? 100 units and increasing to 21 for lgr ? 120 units. 相似文献
15.
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
16.
K. Bodek M. Hugi J. Lang R. Müller E. Ungricht K. Jankowski W. Zipper L. Jarczyk A. Strzałkowski G. Willim H. Witała 《Nuclear Physics A》1980,339(2):353-364
The angular distributions of the energy spectra of the light charged particles (p, d and α) from the 9Be + 28Si reaction have been measured in the energy range 12 ≦ Elab ≦ 30 MeV. The particle evaporation spectra and the angular distributions were analyzed with a spin dependent statistical model. Angular distributions of 9Be ions elastically scattered on 28Si have been measured at the energies 12 MeV, 17 MeV, 23 MeV and 30 MeV and were analysed, together with previously measured cross sections, with the optical model. The fusion cut-off angular momentum lfus(E), the fusion cross section σfus(E) and the ratio σfus/σROM(E) were deduced. The excitation function for fusion was analyzed with the Glas and Mosel model. The parameters obtained from the fusion excitation function were compared with the corresponding ones from the 9Be + 28Si optical-model interaction potential. 相似文献
17.
We have measured fragment kinetic energies in electron induced fission of 232Th for electron energies in the range 7 MeV ≦ Ee ≦ 66 MeV. The relative contribution of the distribution peak associated with high fragment kinetic energies decreases continuously with electron energy. This is interpreted as a relative increase of the symmetric fission yield as compared to the asymmetric fission yield; this fact in turn indicates a non-negligible increase in the average excitation of the fissioning nucleus, with the energy of the bombarding electrons, even above the giant dipole resonance. 相似文献
18.
K.A. Geoffroy J.B. Natowitz R. Eggers P. Kasiraj M.N. Namboodiri 《Nuclear Physics A》1978,302(1):333-342
The emission of prompt γ-radiation in the de-excitation of the products of the reactions of 120 MeV 20Ne with 27Al has been studied. Three NaI detectors placed at angles of 35°, 90° and 145° to the direction of the 20Ne beam were used to detect γ-rays in coincidence with reaction products having 6 ≦ Z ≦ 20, detected in a counter telescope. Data were obtained with the counter telescope in the same plane, as well as in a plane perpendicular to the plane defined by the beam and the NaI detectors. The average multiplicities 〈Mγ〉, average energies 〈Eγ〉, primary γ-ray energy spectra and the variation of 〈Mγ〉 and 〈Eγ〉 with angle of observation and kinetic energy of the detected products are presented and discussed in terms of the dominant reaction mechanisms. 相似文献
19.
H. H. Deubler K. Lekkas P. Sperr K. Dietrich 《Zeitschrift für Physik A Hadrons and Nuclei》1978,284(2):237-244
The process of instantaneous fission in deep inelastic collisions is investigated in a classical model. Kinetic energies and angular distributions of the fragments are calculated for the proposed reaction Pb+U atE cm inc =750 MeV; an experimental setup for the separation of the fragments originating from instantaneous fission from the fragments of thermal fission is explained. We also discuss fusion following instantaneous fission as a mechanism for the production of superheavy elements and arrive at rather promising estimates. 相似文献
20.
The angular distributions of fragments from neutron-induced fission of 232Th have been measured by means of glass detectors in the range 12.2 MeV ≦ En ≦ 18.3 MeV. The behaviour of the angular anisotropy is analysed and the contribution of the (n, 2n′f) process is discussed. 相似文献