Study of Mass-Asymmetric Fission of 180,190 Hg Formed in the 36 Ar + 144,154 Sm Reactions
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y of Mass-Asymmetric Fission of 180,190Hg Formed in the 36Ar + 144,154Sm Reactions D. Kumara, *, E. M. Kozulina, M. Cheralua, G. N. Knyazhevaa, I. M. Itkisa, M. G. Itkisa, K. V. Novikova, A. A. Bogacheva, N. I. Kozulinaa, I. N. Diatlova, I. V. Pchelintseva, I. V. Vorobieva, T. Banerjeea, Y. S. Mukhamejanova, b, A. N. Pana, b, c, V. V. Saikoa, P. P. Singhd, R. N. Sahood, A. N. Andreyeve, D. M. Filipescuf, M. Maitig, R. Prajapatg, and R. Kumarg a
Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research, Dubna, Moscow oblast, 141980 Russia bAl-Farabi Kazakh National University, Almaty, 050040 Kazakhstan cInstitute of Nuclear Physics, Almaty, 050032 Kazakhstan dDepartment of Physics, Indian Institute of Technology—Ropar, Punjab, 140001 India eDepartment of Physics, University of York, York, YO10 5DD, United Kingdom fHoria Hulubei National Institute for Physics and Nuclear Engineering, Magurele, Bucharest, 077125 Romania gDepartment of Physics, Indian Institute of Technology Roorkee, Roorkee, 247667 India *e-mail: [email protected] Received March 2, 2020; revised April 15, 2020; accepted April 27, 2020
Abstract—The mass–energy distributions of fission fragments of excited 180,190Hg nuclei formed in 36Ar + 144,154Sm reactions are measured at incident 36Ar energies of 158, 181, and 222 MeV using the double-arm time-of-flight spectrometer CORSET. The asymmetric fission of 180,190Hg with the most probable masses of light and heavy fragments of 79 and 101 amu, and 84 and 106 amu, respectively, is observed in mass distributions of 180,190Hg at energies of excitation of up to 75 MeV. Two components manifesting the symmetric and asymmetric fission modes are observed in the kinetic energy distributions. DOI: 10.3103/S1062873820080213
INTRODUCTION The mass and energy distributions of fragments of spontaneous and low-energy fission of actinide nuclei have been thoroughly studied [1]. The mass distributions of fission fragments for this region were found to be asymmetric and determined by the strong effect of nuclear shells with Z = 50, N = 82 and a deformed neutron shell with N = 88. The shell effect diminishes as the energy of excitation of fissioning nuclei grows, and the properties of fission fragments become close to those predicted by the liquid-drop model. In contrast to actinide fission, the mass distributions of nuclear fission fragments in the lead region (with masses M ≈ 200 amu) produced in the fusion reactions induced by protons and helium ions, and nuclei in the mass range of 185–210 amu have been found to be symmetric and close to the Gaussian form for most nuclei. However, flatter mass distributions have been found for several nuclei (195Au, 198Hg, and 201Tl) with mass in the region of 200 amu [2, 3]. An asymmetric mass distribution of the fission fragments of daughter nucleus 180Hg with excitation energy E* < 10.8 MeV was recently revealed in experi-
ments on the β-decay of the 180Tl nucleus [4]. Note that the formation of two fragments, semi-magic nuclei 90Zr (N = 50, Z = 40), should be expe
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