0000000000073335
AUTHOR
M. G. Itkis
Asymmetric and symmetric fission of excited nuclei of Hg180,190 and Pb184,192,202 formed in the reactions with Ar36 and Ca40,48 ions
Background: Observation of asymmetric fission of $^{180}\mathrm{Hg}$ has led to intensive theoretical and experimental studies of fission of neutron-deficient nuclei in the lead region.Purpose: The study of asymmetric and symmetric fission modes of $^{180,190}\mathrm{Hg}$ and $^{184,192,202}\mathrm{Pb}$ nuclei.Methods: Mass-energy distributions of fission fragments of $^{180,190}\mathrm{Hg}$ and $^{184}\mathrm{Pb}$ formed in the $^{36}\mathrm{Ar}+^{144,154}\mathrm{Sm}$ and $^{40}\mathrm{Ca}+^{144}\mathrm{Sm}$ reactions, respectively, at energies near the Coulomb barrier have been measured using the double-arm time-of-flight spectrometer CORSET and compared with previously measured $^{192,20…
Fission and quasifission of composite systems with Z=108−120 : Transition from heavy-ion reactions involving S and Ca to Ti and Ni ions
Background: Suppression of compound nucleus formation in the reactions with heavy ions by a quasifission process in dependence on the reaction entrance channel.
Fusion-fission and quasifission of superheavy systems withZ=110–116formed inCa48-induced reactions
Background: In heavy-ion-induced reactions the mechanism leading to the formation of the compound nucleus and the role of quasifission is still not clear.Purpose: Investigation of the quasifission process of superheavy composite systems with $Z=110\text{\ensuremath{-}}116$ and comparison with properties of fusion-fission and quasifission of lighter composite systems.Method: Mass and energy distributions of fissionlike fragments formed in the reactions $^{48}\mathrm{Ca}+^{232}\mathrm{Th}$, ${}^{238}\mathrm{U}$, ${}^{244}\mathrm{Pu}$, and ${}^{248}\mathrm{Cm}$ at energies near the Coulomb barrier have been measured using the double-arm time-of-flight spectrometer CORSET at the U-400 cyclotron…
Fission of 180,182,183Hg* and 178Pt* nuclei at intermediate excitation energies
Purpose: The study of asymmetric and symmetric fission of 180,182,183Hg and 178Pt nuclei as a function of their excitation energy and isospin. Methods: Mass-energy distributions of fission fragments of 180Hg, 178Pt (two protons less than 180Hg), and 182Hg (two neutrons more than 180Hg) formed in the 36Ar+144Sm,142Nd, and 40Ca+142Nd reactions were measured at energies near and above the Coulomb barrier. Fission of 183Hg obtained in the reaction of 40Ca with 143Nd was also investigated to see if one extra neutron could lead to dramatic changes in the fission process due to the shape-staggering effect in radii, known in 183Hg. The measurements were performed with the double-arm time-of-flight …
Asymmetric and symmetric fission of excited nuclei of 180,190Hg and 184,192,202Pb formed in the reactions with 36Ar and 40,48Ca ions
Background: Observation of asymmetric fission of 180Hg has led to intensive theoretical and experimental studies of fission of neutron-deficient nuclei in the lead region. Purpose: The study of asymmetric and symmetric fission modes of 180,190Hg and 184,192,202Pb nuclei. Methods: Mass-energy distributions of fission fragments of 180,190Hg and 184Pb formed in the 36Ar+144,154Sm and 40Ca+144Sm reactions, respectively, at energies near the Coulomb barrier have been measured using the double-arm time-of-flight spectrometer CORSET and compared with previously measured 192,202Pb isotopes produced in the 48Ca+144,154Sm reactions. The mass distributions for 180,190Hg and 184,192,202Pb together with…
Fusion-fission and quasifission of superheavy systems with Z=110-116 formed in Ca 48 -induced reactions
Background: In heavy-ion-induced reactions the mechanism leading to the formation of the compound nucleus and the role of quasifission is still not clear. Purpose: Investigation of the quasifission process of superheavy composite systems with Z = 110-116 and comparison with properties of fusion-fission and quasifission of lighter composite systems. Method: Mass and energy distributions of fissionlike fragments formed in the reactions 48Ca +232 Th, 238U, 244Pu, and 248Cm at energies near the Coulomb barrier have been measured using the double-arm time-of-flight spectrometer CORSET at the U-400 cyclotron of the FLNR JINR. Results: The most probable fragment masses as well as total kinetic ene…
Shell effects in damped collisions ofSr88withYb176at the Coulomb barrier energy
This work is a study of the influence of shell effects on the formation of binary fragments in damped collision. We have investigated binary reaction channels of the composite system with $Z=108$ produced in the reaction $^{88}\mathrm{Sr}$${+}^{176}$Yb at an energy slightly above the Bass barrier (${E}_{\text{c.m.}}/{E}_{\text{Bass}}=1.03$). Reaction products were detected by using the two-arm time-of-flight spectrometer CORSET at the K130 cyclotron of the Department of Physics, University of Jyv\"askyl\"a. The mass-energy distribution of primary binary fragments has been measured. For targetlike fragments heavier than 190 u, which correspond to a mass transfer as large as twenty nucleons o…
Investigation of the reaction 64Ni+238U being an option of synthesizing element 120
This study is concerned with the search for entrance channels suitable to synthesize elements with Z > 118. Mass-energy distributions as well as capture cross-sections of fission-like fragments have been measured for the reactions 64Ni + 238U → 302120 and 48Ca + 238U → 286112 at energies near the Coulomb barrier. Compound nucleus fission cross-sections were estimated from the analysis of mass and total kinetic energy distributions. The cross-section drops three orders of magnitude for the formation of the compound nucleus with Z = 120 obtained in the reaction 64Ni + 238U compared to the formation of the compound nucleus with Z = 112 obtained in the reaction 48Ca + 238U at an excitation ener…
Neutron and gamma-ray emission in the proton induced fission of 238U and 242Pu
Abstract Average prescission Mpren and postscission Mpostn neutron multiplicities as well as average γ-ray multiplicity 〈Mγ〉, average energy 〈Eγ〉 emitted by γ-rays as a function of mass and total kinetic energy (TKE) of fission fragments were measured in proton induced reactions p+ 242 Pu→ 243 Am , p+ 238 U→ 239 Np at proton energy Ep=13, 20 and 55 MeV.
Investigation of fusion probabilities in the reactions with 52,54Cr, 64Ni, and 68Zn ions leading to the formation of Z = 120 superheavy composite systems
Background: The formation of superheavy nuclei in fusion reactions is suppressed by a competing quasifission process. The competition between the formation of the compound nucleus and the quasifission depends strongly on the reaction entrance channel. Purpose: The investigation of fission and quasifission processes in the formation of Z=120 superheavy composite systems in the 52,54Cr+248Cm and 68Zn+232Th reactions, and their comparison with the 64Ni+238U reaction at energies in the vicinity of the Coulomb barrier. Methods: Mass-energy distributions of fissionlike fragments formed in the reactions 52,54Cr+248Cm and 68Zn+232Th at energies near the Coulomb barrier were measured using the doubl…
Mass distributions of the system136Xe+208Pb at laboratory energies around the Coulomb barrier: A candidate reaction for the production of neutron-rich nuclei atN=126
Reaction products from the system ${}^{136}\mathrm{Xe}+{}^{208}$Pb at ${}^{136}$Xe ions laboratory energies of 700, 870, and 1020 MeV were studied by two-body kinematics and by a catcher-foil activity analysis to explore the theoretically proposed suitability of such reaction as a means to produce neutron-rich nuclei in the neutron shell closure $N=126$. Cross sections for products heavier than ${}^{208}$Pb were measured and were found sensibly larger than new theoretical predictions. Transfers of up to 16 nucleons from Xe to Pb were observed.
Shell effects in damped collisions of Sr-88 with Yb-176 at the Coulomb barrier energy
[Introduction] This work is a study of the influence of shell effects on the formation of binary fragments in damped collision. We have investigated binary reaction channels of the composite system with Z = 108 produced in the reaction 88 Sr + 176 Yb at an energy slightly above the Bass barrier ( E c.m. /E Bass = 1 . 03). Reaction products were detected by using the two-arm time-of-flight spectrometer CORSET at the K130 cyclotron of the Department of Physics, University of Jyv ̈ askyl ̈ a. The mass-energy distribution of primary binary fragments has been measured. For targetlike fragments heavier than 190 u, which correspond to a mass transfer as large as twenty nucleons or more, an enhance…
Spin distribution measurement for 64Ni + 100Mo at near and above barrier energies
Spin distribution measurements were performed for the reaction 64 Ni + 100 Mo at three beam energies ranging from 230 to 260 MeV. Compound nucleus (CN) spin distributions were obtained channel selective for each evaporation residue populated by the de-excitation cascade. A comparison of the spin distribution at different beam energies indicates that its slope becomes steeper and steeper with increasing beam energy. This change in slope of the spin distribution is mainly due to the onset of fission competition with particle evaporation at higher beam energies.
Fusion suppression in mass-asymmetric reactions leading to Ra compound nuclei
Near-barrier excitation functions have been measured for evaporation-residue production and fission in the 12C + 204,206,208Pb and 48Ca + 168,170Er systems that lead to the compound nuclei 216,218,220Ra*. A Pronounced suppression of evaporation-residue production is observed for the more symmetric combinations, 48Ca + 168,170Er. We relate this to the significant quasifission components already observed for these systems.