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1.
LIU Guo-Xing 《中国物理C(英文版)》1987,11(1):98-103
The angular distributions of fission fragments are measured for systems of 120MeV 14N+118Sn with mica track detectors and gold-surfacebarrier silicon detectors. The measured angular distributions can be fitted by the standard theory of fission angular distributions on the basis of statistical model. The effective moments of inertia of fissioning nuclei at saddle point are derived from angular distribution anisotropies. The shapes of saddle point of fissioning nuclei in the region of Z2/A<30 are discussed. 相似文献
2.
LIU Guo-Xing CHEN Ke-Liang ZHENG Ji-Wen WANG Su-Fang BAI Xing-Ping YU Xian FAN Zhi-Guo 《中国物理C(英文版)》1989,13(8):733-739
The angular distributions of fission fragments for a series of compound nuclei formed in the bombardment of 181Ta,197Au Pb and 209Bi by 12C ions and in the bombardment of natural lead by 14N ions were measu ed with mica track detectors and gold surface barrier detectors.It is shown that all experimental data for the fission fragment angular distributions can be fitted by the statistical scission model of fission fragment angular distribution. 相似文献
3.
Angular distributions of fission fragment and fission excitations was measured for a series of reactions 12C+169Tm, 175Lu, 181Ta, W, Re, Pt, 197Au, Pb and 209Bi in the 57.0—73.0MeV energy region with mica detectors and gold surface barrier silicon detectors. The experimental values <Γf/Γn> we are abtained from fission excitation functions and compared to theoretical ones. The variation of the experimental values for the fission barrier height with the mass number A of the compound nuclei was studied and compared to the theoretical predictions by the liquid drop medel. 相似文献
4.
ANGULAR DISTRIBUTIONS OF FISSION FRAGMENTS AND THE SHAPES OF THE SADDLE POINT OF COMPOUND NUCLEI
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LIU GOU-XING WANG ZJO-GOU YIN SHU-ZHI HAO BIN-GAN YUAN SHUANG-GUI XIA XING-SHUO 《中国物理C(英文版)》1978,2(3):242-248
We have measured the angular distributions of fission fragments for a series of compound nuclei formed in the bombardment of 169Tm, 175Lu, 181Ta, 197Au, 209Bi, 232Th and 238U by 78 MeV 12C ions and in the bombardment of natural lead by 96.6, 92.2, 88.1, 79.0 and 75.6 MeV 14N ions with mica track detectors. All the measured angular distributions can be fitted by the theoretical formula given by Halpern and Strutinski. The effective moments of inertia of the fissioning nuclei at the saddle point are derived from the angular distribution anisotropies. A comparison is made for the shapes of experimental saddle point with the theoretical predictions by the liquid drop model. 相似文献
5.
The fission cross sections and the evaporation residue cross sections for 12C+209Bi and 14N+Pb reactions were measured with the gold surface barrier silicon detectors and the mica nuclear track detectors.The critical angular momentum ler was deduced from the measured evaporation residue cross section σer on the basis of the sharp-off model.The fission barrier with the particular angular momentum i derived from the condition Γf/Γn=1 at l=le The angular momentum effect of the fission barrier was studied experimentally. 相似文献
6.
RADIOCHEMICAL INVESTIGATION OF MASS DISTRIBUTIONS IN 12C-INDUCED FISSION OF 209Bi AND 238U
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The yields of 15 and 17 fission, products have been obtained by radiochemical determinations in 12C-induced fission of 209Bi and 238U respectively. From these data, the mass distributions of fission fragments are calculated based on three different hypotheses for the charge distribution. The results seem to indicate that the hypothesis of equal charge displacement gives the best fit to the Gaussian distribution for the masses of the fission fragments. By comparison with the mass distributions for 209Bi (12C, f), 238U(12C, f) and 197Au(12C, f) in our early measurement, we find that for fission parameter Z2/A>37, the width of the mass distributions increases with Z2/A rapidly. 相似文献
7.
The fission cross section and fission probability of 197Au, induced by (1665 MeV) π-, have been studied using CR-39 track detectors. A 4π-geometry was used to count track statistics. A beam of negative pions of 1665 MeV was produced at AGS of Brookhaven National Laboratory, USA, and allowed to fall normally on the stack. Two detectors from the stack were scanned for fission fragment tracks after etching in 6N NaOH at 70℃. The statistics of fission fragment tracks in both detectors were obtained. It was found that there was a marked asymmetry of registered tracks with respect to the forward and backward hemispheres. This asymmetry could be partly accounted for on the basis of momentum transfer to the struck nucleus. On the basis of counting statistics fission cross section was measured, and fission probability was determined by dividing the fission cross section with the reaction cross section. The fission cross-section and fission probability were compared with the computed values using the cascade-exciton model code CEM95. 相似文献
8.
WU He-Yu DAI Guang-Xi CAI Wei QI Yu-Jin YAN De-Hong ZHANG Bao-Guo DANG Bing-Rong LUO Qin-Zheng QIAN Xing WEN Wan-Xin 《中国物理C(英文版)》1993,17(8):680-684
Alternative layers of target material,which were prepared by evaporating 209Bi on the surface of mica foils,were irradiated with 12C ions.Ternary fission events in which three fragments of comparable mass were produced in 2525-47.5MeV/A 12C+209Bi reaction,were recorded by the mica detectors with 2π geometry.The observed probability ratio of ternary fission relative to binary fission in 2π geometry was modified to 4π geometry spatial in terms of the Monte Carlo method.The values of ratioes increase with the bombarding energy,and are compared with the calculation result of the cascade fission model. 相似文献
9.
Excitation Energy and Temperature of Compound Nuclei in the Reaction of 35MeV/u 40Ar+197Au
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DUAN Li-Min WU He-Yu JIN Gen-Ming WANG Su-Fang LI Zu-Yu WEI Zhi-Yong ZHANG Bao-Guo WANG Hong-Wei XIAO Zhi-Gang LIU Yong-Ying HU Pei-Gang LU Zhao-Hui TIAN Wen-Dong GOU Quan-Bu 《中国物理C(英文版)》2003,27(2):118-123
The fission fragments in the reaction of 40Ar+197Au have been measured coincidently with light charged particles at 35MeV/u by using large area position sensitive detectors and Si-detectors. The velocities of the fissioning compounds are deduced based on the fragments and the excitation energies of the compounds calculated with a hypothesis of massive transfer and taking into account the influence of pre-equilibrium emission of light particles. As the same time,the temperatures of the compounds are extracted by using the energy spectra of the backward light charged particles measured coincidently with fission fragments. The temperature-excitation energy curve does not present the behaviour predicted by the theories. 相似文献
10.
Temperatures and Excitation Energies of Hot Nuclei in Reactions of 40Ar+natAg,209Bi at MeV/u
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Yin Shuzhi Jin Weiyang Zhang Chun Jin Genming Zheng Jiwen Wu Enjiu Tan Jilian Li Zuyu Wang Sufang Song Mingtao Wu Heyu He Zhiyong Jiang Dongxing Qian Xing 《中国物理C(英文版)》1997,21(8):680-685
Coincidence measurements of fission fragment and light charged particle have been perfotrmed for the reactions of 40Ar+natAg,209Bi at E/A=25MeV using 4 PPAC and 11 sets of ΔE-E telescopes.Angular correlations of fission fragment were ploted as a function of the folding angle between the two detected fission fragments.The linear momentum transfer distributions were derived by measuring angular correlations.The backward spectra of light particles detected in coincidence with fission fragments having different average〈LMT〉are analyzed with Maxwell distribution.After some corrections the initial temperatures of the hot nuclei are determined from the energy spectra.The excitation energies corresponding to the different average〈LMT〉are obtained considering the reaction Q values and pre-equilibrum emission.In the central collision of the 40Ar+natAg,209Bi reactions,excitation energies are measured to be about 4.2MeV/u,2.4MeV/u and temperatures about 6.1MeV,5.5MeV,respecdvely.In semi-central collision,excitaionen energies are measured to be about 3.5MeV/u,1.9MeV/u and temperatures about 5.8MeV,4.8MeV respectively. 相似文献
11.
Angular distributions of light charged particles from 252Cf fission in the ranges 0–46° and 134–180°
A.J. Kordyasz E. Piasecki L. Nowicki P. Koczoń J. Sobolewski M. Kisieliński W. Czarnackif 《Nuclear Physics A》1985,439(1):28-44
Alpha particles, tritons, deuterons and protons accompanying 252Cf fission were registered in coincidence with both fission fragments by means of a system containing two-dimensional position-sensitive silicon detectors. Angular distributions, kinetic energy spectra of light charged particles as well as mass distributions of fission fragments in coincidence with light charged particles were measured. The experimental results are compared with some theoretical models. 相似文献
12.
Liu Zuhua Xu Jincheng Zhang Huanqiao Qian Xing Qiao Yu Lin Chengjian Xu Kan 《中国物理C(英文版)》1994,18(6):489-495
We have succeeded in isolating the complete arising from complete fusion-fission in terms of the fragment folding angle technique,and measured complete fusion-fission cross sections and fragment angular distributions for the 16O+232Th system in the center-of-mass energies between 72.61 and 80.11 MeV.The observed fission excitation function is in quite good agreement with the expectation of the coupled-channels theory.However,the measured fragment angular distributions are more anisotropic than the predictions of both the saddle-point transition-state model and scission model. 相似文献
13.
Measurements have been made, by means of mica nuclear track detectors, of the distributions in tracklength and the angular distributions with respect to the beam direction for the fission fragments from the systems Ag, Te and Au plus 80-MeV alpha particles. Analysis of the tracklength distributions indicated that, in each case, full momentum transfer from the incident projectile characterized those interactions that led to fission. Angular-momentum dependent statistical model calculations for the decay of the respective compound nuclei then provided information on fission-evaporation competition in the de-excitation processes, and in particular the distribution in nuclear temperature and angular momentum at which the fission events took place. This information was then employed in the analysis of the measured fission fragment angular distributions, and to extractK 0 2 values. From these, the moments of inertia of the fission saddle point shapes were calculated, and the results are in good agreement with theoretical estimates. 相似文献
14.
THE MEASUREMENT OF COMPLETE FUSION CROSS-SECTIONS FOR THE REACTIONS 12C+27Al, 12C+209Bi AND 14N+Pb
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Mica track detectors were used for the measurement of evaporation residues and fission fragments of compound nuclei formed in 12C+27Al, 12C+209Bi and 14N+Pb reactions. The complete fusion cross-sections and excitation functions were then obtained. By using the sharp cut-off model approximation, the values of the critical angular momenta were extracted from the complete fusion cross-sections. The results obtained were compared with the calculations based on current theories for critical angular momentum; they were found to agree within experimental uncertainties. 相似文献
15.
Linear Momentum Transfer in the Reactions Induced by 50MeV/A12C Bombarding 209Bi and 197Au
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JIANG Dong-Xing YE Yan-Lin LIU Hong-Tao LU Xi-Ting HUANG Xiao-Lin XIAO Bin ZHAN Wen-Long ZHU Yong-Tai GUO Zhong-Yan FENG En-Pu XI Hong-Fei LIU Guan-Hua ZHOU Jian-Qun YIN Shu-Zhi ZHU Xiang WANG Bing FENG Jun 《中国物理C(英文版)》1992,16(6):556-562
The Distributions of the linear momentum transfer (LMT) in the reactions induced by 50MeV/u 12C with 209Bi and 197Au were measured using fission fragment angular correlation technique.The most probable value of the linear momentum transfer per projectile,pmp is dependent on the target.173MeV/c and 184MeV/c for 209Bi and 197Au were obtained.In these distributions,there exists a small hump around 0.3 of LMT,which can probably be attributed to the alpha cluster transfer. 相似文献
16.
Based on the statistical fission theory, we have calculated the mass and kinetic energy distributions as well as other physical quantities of 235U fission induced by thermal neutron using microscopical method. That is, the quantum state densities of the fragments at scission point are calculated by means of BCS hamiltonian. The contribution of the collective deformation of fragments to the quantum state density has been taken into consideration. The potential energy of fragment is calculated by means of Strutinski procedure, and the shelling effect, pairing correlation as well as collective deformation have been taken into consideration in calculating the excitation energy at scission point. The scission point distance is treated as an adjustable parameter.Comparing with other statistical fission theories, our results give better agreement with existing experiments. 相似文献
17.
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
18.
Ternary fission in ^197Au+^197Au collisions at 15 A MeV is investigated by using the improved quantum molecular dynamical (ImQMD) model. The experimental mass distributions for each of the three fragments are reproduced for the first time without any freely adjusting parameters. The mechanisms of ternary fission in central and semicentral collisions are dynamically studied. In direct prolate ternary fission, two necks are found to be formed almost simultaneously and rupture sequentially in a very short time interval. Direct oblate ternary fission is a very rare fission event, in which three necks are formed and rupture simultaneously, forming three equally sized fragments along space-symmetric directions in the reaction plane. In sequential ternary fission a binary division is followed by another binary fission event after hundreds of fm/c. 相似文献
19.
Fission Fragment Angular Correlation in the Reaction Induced by 84.0MeV 16O Bombarded 238U
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QIAN Xing ZHANG Huan-Qiao LIU Zu-Hua XU Jin-Cheng CHEN Shao-Lin XU Kan LU Li-Xin 《中国物理C(英文版)》1993,17(2):173-178
Fission fragment angular distribution and angular correlation in the reaction induced by 84.0MeV 16O bombarded 238U have been measured by using two position-sensitive PPAC with large area.Transfer fission has been removed from total fission using fission fragment angular correlation technique.The contribution to the total fission cross section arising from transfer is about 10%.The anisotropy of fission fragment for transfer-fission is rather small,thus the removal of the transfer fission has little effect on the total fragment angular distribution.Indeed the anisotropy becomes larger by about 5% and anomalously anisotropies still persist. 相似文献
20.
X.C. Feng Y.X. Guo X.H. Zhou X.F. Sun X.G. Lei W.X. Huang J.J. He Z. Liu Y.H. Zhang S.F. Zhu Y.X. Luo S.X. Wen G.J. Yuan X.G. Wu 《The European Physical Journal A - Hadrons and Nuclei》1999,6(3):235-237
The high-spin states of 206At have been studied in the reaction 197Au (12C,3n) 206At at 12C energies from 60 to 80 MeV. In-beam measurements of %-ray excitation functions, %-%-t coincidences, and %-ray angular distributions were carried out with seven BGO(AC)HPGe detectors and one intrinsic Ge planar detector. A level scheme for 206At with 25 % rays was established for the first time, including a 10m isomer with a measured half-life of 410 - 80 ns. The level scheme of 206At consists of two disconnected cascades, probably corresponding to the proton excitations and the neutron-hole excitations, respectively. 相似文献