共查询到20条相似文献,搜索用时 15 毫秒
1.
A. I. Svirikhin V. N. Dushin M. L. Chelnokov V. I. Chepigin I. N. Izosimov D. E. Katrasev O. N. Malyshev A. Minkova A. G. Popeko E. A. Sokol A. V. Yeremin 《The European Physical Journal A - Hadrons and Nuclei》2010,44(3):393-396
The neutron-deficient isotope 246Fm , produced in the complete fusion reaction 40Ar$ + $208Pb , was investigated. The main goal of the experiment was to determine the neutron multiplicity at spontaneous fission of this isotope. For experiments aimed at the study of spontaneous fission of transfermium nuclei improvements in the focal plane detector system of recoil separator VASSILISSA have been made. A neutron detector consisting of 54 3He -filled counters has been mounted around the focal-plane detector chamber. From the experimental data the average number of neutrons per spontaneous fission of 246Fm was determined ( $ \bar{{\nu}}$ = 3.55±0.5) . 相似文献
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The monopole and quadrupole pairing effects on the fission mass tensor are considered. Two possible definitions of the quadrupole pairing matrix elements are investigated. They differ in dependence on deformation, leading to different behavior of the mass parameter with changing deformation. The effects of the usually neglected RPA terms are given in a simple expression. With monopole pairing alone the RPA terms do not contribute to the mass tensor, whereas the quadrupole pairing may have significant effects. Quantitative studies are carried out for a simple model which contains the important realistic features. 相似文献
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The final period of nuclear fission is discussed. We propose the following picture: Nuclear scission happens because of an hydrodynamic instability triggered by random surface vibrations. Thus the scissioning complex ruptures at random positions. Measured total kinetic energies point to the very relevance of the instability, while the randomness of rupture shows up in neutron emission data. 相似文献
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W. Urban J.L. Durell W.R. Phillips A.G. Smith M.A. Jones I. Ahmad A.R. Barnett M. Bentaleb S.J. Dorning M.J. Leddy E. Lubkiewicz L.R. Morss T. Rzaca-Urban R.A. Sareen N. Schulz B.J. Varley 《Zeitschrift für Physik A Hadrons and Nuclei》1997,358(2):145-151
Prompt γ radiation following spontaneous fission has been measured using the EUROGAM 2 array. Using these data and newly developed analysis techniques a number of subjects were studied, which are briefly discussed. One of these subjects, shape transition in A≈100 Sr and Zr nuclei is discussed in more detail. Quadrupole moments were determined for rotational bands in the N=58,59,60,62 and 64 Sr and Zr isotopes. Deformation parameters, which increase from β2 ≈ 0.1 at N=56 to β2 ≈ 0.4 at N=64, suggest that in strontium and zirconium isotopes shape change happens gradually between N=56 and N=62 and is probably due to an occupancy of three or more deformation-driving orbitals of h11/2 parentage. 相似文献
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S. G. Kadmensky L. V. Titova N. O. Dronov 《Bulletin of the Russian Academy of Sciences: Physics》2013,77(4):424-426
The problem of describing T-odd asymmetries in ternary fission reactions of oriented nuclei is solved for the first time on the basis of quantum theory. Estimates of the T-odd asymmetry coefficients in the angular distributions of the reaction products are obtained using the spin density matrix of the oriented fissioning nucleus. It is demonstrated that experiments on observing T-odd asymmetries in the spontaneous fission of oriented nuclei are of interest because the T-odd asymmetry coefficients can be around an order of magnitude greater than similar coefficients in the fission of unoriented target nuclei induced by polarized neutrons. 相似文献
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D. Fong J. H. Hamilton A. V. Ramayya J. K. Hwang C. Goodin K. Li J. Kormicki J. O. Rasmussen Y. X. Luo S. C. Wu I. Y. Lee A. V. Daniel G. M. Ter-Akopian G. S. Popeko A. S. Fomichev A. M. Rodin Yu. Ts. Oganessian M. Jandel J. Kliman L. Krupa J. D. Cole M. A. Stoyer R. Donangelo W. C. Ma 《Physics of Atomic Nuclei》2006,69(7):1161-1167
The hot bimodal fission of 252Cf is reexamined with new high-statistics data. We constructed a γ-γ-γ coincidence cube for binary fission and LCP-gated γ-γ matrix for ternary fission. By identifying the secondary fission fragments from their γ-ray transitions, we measured the yields for various fission splits. The normal neutron yield distribution is found to be
Gaussian for Xe-Ru. However, the binary fission split of Ba-Mo is found to exhibit a bimodal neutron distribution with the
“hot mode” corresponding to ≈3.1% of the total yield. In α ternary fission, the first measurements of yields for specific fission splits are presented. The Te-α-Ru and Xe-α-Mo neutron yields fit well with a single mode, but the Ba-α-Zr split shows evidence for an enhanced hot mode with an intensity of ≈13.8% of the normal mode.
The text was submitted by the authors in English. 相似文献
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A. Hotzel P. Thirolf Ch. Ender D. Schwalm M. Mutterer P. Singer M. Klemens J. P. Theobald M. Hesse F. Gönnenwein H. v. d. Ploeg 《Zeitschrift für Physik A Hadrons and Nuclei》1996,356(1):299-308
Theγ-ray spectrum of252Cf(sf) was measured in the Darmstadt-Heidelberg Crystal Ball spectrometer, with a double ionization chamber mounted inside to detect the fission fragments. The measurement was aimed at a better understanding of an unusual component found in the high-energy region between 3 and 8 MeV, with fragment mass splits near symmetry. This component was proved to be predominantly emitted by the heavier fragment, to reach its highest intensity at a fragment mass split of 132:120, and to have an almost isotropic angular distribution. Calculations with the statistical code CASCADE could reproduce the main features. 相似文献
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A. Hotzel P. Thirolf Ch. Ender D. Schwalm M. Mutterer P. Singer M. Klemens J. P. Theobald M. Hesse F. Gönnenwein H. v. d. Ploeg 《Zeitschrift für Physik A Hadrons and Nuclei》1987,356(3):299-308
The γ-ray spectrum of 252Cf(sf) was measured in the Darmstadt-Heidelberg Crystal Ball spectrometer, with a double ionization chamber mounted inside to detect the fission fragments. The measurement was aimed at a better understanding of an unusual component found in the high-energy region between 3 and 8 MeV, with fragment mass splits near symmetry. This component was proved to be predominantly emitted by the heavier fragment, to reach its highest intensity at a fragment mass split of 132:120, and to have an almost isotropic angular distribution. Calculations with the statistical code CASCADE could reproduce the main features. 相似文献
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J. H. Hamilton A. V. Ramayya J. K. Hwang G. M. Ter-Akopian A. V. Daniel J. O. Rasmussen S. -C. Wu R. Donangelo C. J. Beyer J. Kormicki X. Q. Zhang A. M. Rodin A. S. Fomichev G. S. Popeko J. Kliman L. Krupa M. Jandel Yu. Ts. Oganessian G. Chubarian D. Seweryniak R. V. F. Janssens W. C. Ma R. B. Piercey W. Greiner J. D. Cole 《Physics of Atomic Nuclei》2002,65(4):645-652
The spontaneous fission (SF) of 252Cf has been studied via γ-γ-γ coincidence and light charged particle—γ-γ coincidence with Gammasphere. The yields of correlated Mo-Ba pairs in binary fission with 0–10 neutron emission have been remeasured with an uncompressed cube. The previous hot fission mode with 8–10 neutron emission seen in the Mo-Ba split is found to be smaller than earlier results but still present. New 0n binary SF yields are reported. By gating on the light charged particles detected in ΔE-E detectors and γ-γ coincidence with Gammasphere, the relative yields of correlated pairs in alpha ternary fission with zero to 6n emission are observed for the first time. The peak occurs around the α2n channel. A number of correlated pairs are identified in ternary fission with 10Be as the light charged particle. We observed only cold, 0n 10Be and little, if any, hot, xn 10Be channels. 相似文献
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C. Grégoire H. Delagrange K. Pomorski K. Dietrich 《Zeitschrift für Physik A Hadrons and Nuclei》1988,329(4):497-502
So far theoretical investigations on the abnormal emission of light particles in competition with fission have dealt only with the total number of emitted particles. In this study, a first step in calculations of energy spectra is attempted in the framework of a transport equation describing the evolution of an excited nucleus toward fission. We stress the role of differential multiplicities as qualified probes to gain knowledge on the dynamical evolution of the fission process. 相似文献
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D.C. Biswas R.K. Choudhury M. Cinausero B. Fornal D.V. Shetty G. Viesti D. Fabris E. Fioretto M. Lunardon G. Nebbia G. Prete D. Bazzacco M. DePoli D.R. Napoli C.A. Ur G. Vedovato 《The European Physical Journal A - Hadrons and Nuclei》2000,7(2):189-195
Measurements of fission fragment yields and neutron multiplicities have been carried out for the Mo-Ba fragment pairs in
the spontaneous fission of 252Cf, using the γ-ray spectroscopy technique to analyze γ-γ-γ coincidence data. Prompt γ -ray multiplicities were also measured
as a function of the number of neutrons emitted in the fission process leading to the Mo-Ba partition. We do not observe the
enhancement in the yields of events with high neutron emission multiplicity (νn > 7) that has been associated to a second fission mode leading to the production of hyperdeformed Ba fragments, as reported
in some earlier studies. The average γ-ray multiplicity is found to be rather weakly dependent on the number of neutrons emitted
in the fission process.
Received: 21 July 1999 / Revised version: 19 November 1999 相似文献
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《Physics letters. [Part B]》1987,191(4):339-342
Angular and energy distributions of ternary fission products of 252Cf have been measured with a position sensitive ionization chamber. Most of the observed triple coincidences are light-charged-particle accompanied fission events. The few events registered with relative angles near 120° allow to deduce an upper limit of 10−8 per binary fission for a symmetric ternary fragmentation, in contradiction to previous counting experiments yielding ternary-to-binary fission ratios between 10−4 and 10−6. 相似文献
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《Nuclear Physics A》1999,651(3):237-249
We test the importance of non-axial nuclear shapes in spontaneous fission of heavy and superheavy even-even nuclei from the region around a hypothetical doubly magic nucleus 298114. Fission half-lives are calculated by finding dynamical fission paths as dictated by the least WKB action principle with the macroscopic-microscopic energy and the cranking inertial parameters. Results show that the effects of non-axial shapes on the fission process are weakened by the inertia tensor and become important only for the heaviest elements with Z ⩾ 120. 相似文献
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F. Caïtucoli M. Asghar B. Leroux G. Barreau K. Hamadache A. Sicre T.P. Doan M. Allab 《Nuclear Physics A》1983,394(3):360-368
Fission-fragment mass and kinetic energy distributions and their correlations have been measured for the spontaneous fission of 244Cm. About 3.54 × 105 fission events were collected. The global mass distribution shows shoulders at μH ≈ 134 and μH ≈ 143?144. The peak/valley ratio is 86. The dip ΔEK value at symmetry is 13.4 ± 1.5 MeV. In the yields for high-kinetic-energy selected events, the masses 139 and 144 dominate. The results of 244Cm are compared with the other isotopes of Cm and discussed in terms of the structures present in the potential energy surface of the fissioning system caused by the structures in the nascent fragments. 相似文献