INFLUENCE OF ENTRANCE-CHANNEL SHELL EFFECTS ON FUSION HINDRANCE

2008 ◽  
Vol 17 (01) ◽  
pp. 23-30
Author(s):  
J. BŁOCKI ◽  
J. WILCZYŃSKI
Keyword(s):  
Diffusion Model ◽  
Cross Sections ◽  
Evaporation Residue ◽  
Entrance Channel ◽  
Dynamical Model ◽  
Striking Difference ◽  
Injection Point ◽  
Shell Effects ◽  
Diffusion Stage

A study is presented to what extent a striking difference in the evaporation-residue cross sections for two reactions, 86 Kr + 130 Xe and 86 Kr + 136 Xe , originates from different shell effects in 130 Xe and 136 Xe nuclei. A classical dynamical model with one-body dissipation was used to calculate the injection point to the "diffusion" stage of the Fusion-by-Diffusion model of Światecki, Siwek-Wilczyńska and Wilczyński. Only a factor of 6 in the ratio of the fusion hindrance factors in these two reactions can be associated with the entrance-channel shell effects.

scholarly journals Evaporation-residue cross sections: role of the entrance channel

2011 ◽  
Vol 17 ◽  
pp. 09004 ◽  
Author(s):  
Neil Rowley ◽  
Nabila Saffdine Grar
Keyword(s):  
Cross Sections ◽  
Evaporation Residue ◽  
Entrance Channel

DECAY OF 202Pb* FORMED IN 48Ca+154Sm REACTION USING THE DYNAMICAL CLUSTER-DECAY MODEL

2009 ◽  
Vol 18 (07) ◽  
pp. 1453-1467 ◽  
Author(s):  
SHEFALI KANWAR ◽  
MANOJ K. SHARMA ◽  
BIRBIKRAM SINGH ◽  
RAJ K. GUPTA ◽  
WALTER GREINER
Keyword(s):  
Cross Section ◽  
Compound Nucleus ◽  
Fission Cross Section ◽  
Evaporation Residue ◽  
Entrance Channel ◽  
Cluster Decay ◽  
Excitation Energies ◽  
Shell Effects ◽  
Decay Model ◽  
Symmetric Fission

The decay of compound nucleus 202 Pb *, formed in entrance channel reaction 48 Ca +154 Sm at different incident energies, is studied by using the dynamical cluster-decay model (DCM) where all decay products are calculated as emissions of preformed clusters through the interaction barriers. The calculated results show an excellent agreement with experimental data for the fusion-evaporation residue cross-section σ ER together with the fusion-fission cross-section σ FF (taken as a sum of the energetically favored symmetric [Formula: see text] and near symmetric A=65–75 plus complementary fragments), and the competing, non-compound-nucleus quasi-fission cross-section σ QF where the entrance channel is considered not to loose its identity (and hence with preformation factor P0=1). The interesting feature of this study is that the three decay processes (ER, FF and QF) are quite comparable at low energies, ER being the most dominant, whereas at higher energies FF becomes most probable followed by ER and QF. The prediction of two fission windows, the symmetric fission (SF) and the near symmetric fission (nSF) whose contribution is more at lower incident energies, suggests the presence of a fine structure effect in the fusion-fission of 202 Pb *. This result is attributed to the shell effects (magic shells) playing effective role in the fragment preformation yields for 48 Ca +154 Sm reaction at lower excitation energies, giving rise to "shoulders", to an otherwise Gaussian FF mass distribution, responsible for the QF process. As a further verification of this result, absence of "shoulders" (hence, the QF component) in the decay of 192 Pb * due to 48 Ca +144 Sm reaction is also shown to be given by the calculations, in agreement with experiments. The only parameter of the model is the neck-length ΔR which shows that the ER occurs first, having the largest values of ΔR, and the FF and QF processes occur almost simultaneously at lower incident energies but the FF takes over QF at higher incident energies. In other words, the three processes occur in different time scales, QF competing with FF at lower incident energies.

SHELL CORRECTION ENERGIES IN CALCULATIONS OF THE SURVIVAL PROBABILITY

2005 ◽  
Vol 14 (03) ◽  
pp. 333-339 ◽  
Author(s):  
K. SIWEK-WILCZYŃSKA ◽  
I. SKWIRA ◽  
J. WILCZYŃSKI
Keyword(s):  
Experimental Data ◽  
Cross Sections ◽  
Ground State ◽  
Evaporation Residue ◽  
Shell Correction ◽  
Model Calculations ◽  
Shell Effects ◽  
Fission Barriers ◽  
Shell Correction Energy ◽  
Existing Data

Analysis of existing data on experimental fission barriers for about 90 nuclei shows that the shell correction energy practically vanishes at the barrier configuration. Statistical model calculations, with shell effects accounted for by the Ignatyuk formula, were carried out for the decay of the 248 Cf compound nucleus assuming the ground state shell corrections of Möller et al., and the vanishing shell correction energy at the barrier. The results are consistent with existing experimental data on fusion- and xn evaporation-residue cross sections in the 12 C +236 U reaction.

scholarly journals A Dynamical Study of Fusion Hindrance with Nakajima-Zwanzig Projection Method

2021 ◽  
Author(s):  
Yasuhisa Abe ◽  
David Boilley ◽  
Quentin Hourdillé ◽  
Caiwan Shen
Keyword(s):  
Cross Sections ◽  
Degrees Of Freedom ◽  
Operator Method ◽  
Initial Distribution ◽  
Physical Parameters ◽  
Relaxation Processes ◽  
Fast Variable ◽  
Dynamical Study ◽  
Injection Point ◽  
Slow Variables

Abstract A new framework is proposed for the study of collisions between very heavy ions which lead to the synthesis of Super-Heavy Elements (SHE), to address the fusion hindrance phenomenon. The dynamics of the reaction is studied in terms of collective degrees of freedom undergoing relaxation processes with different time scales. The Nakajima-Zwanzig projection operator method is employed to eliminate fast variable and derive a dynamical equation for the reduced system with only slow variables. There, the time evolution operator is renormalised and an inhomogeneous term appears, which represents a propagation of the given initial distribution. The term results in a slip to the initial values of the slow variables. We expect that gives a dynamical origin of the so-called “injection point s” introduced by Swiatecki et al in order to reproduce absolute values of measured cross sections for SHE. A formula for the slip is given in terms of physical parameters of the system, which confirms the results recently obtained with a Langevin equation, and permits us to compare various incident channels.

Entrance Channel Dependence of Production Cross Sections of Superheavy Nuclei in Cold Fusion Reactions

2005 ◽  
Vol 22 (4) ◽  
pp. 846-849 ◽  
Author(s):  
Feng Zhao-Qing ◽  
Jin Gen-Ming ◽  
Fu Fen ◽  
Zhang Feng-Shou ◽  
Jia Fei ◽  
...  
Keyword(s):  
Cross Sections ◽  
Production Cross ◽  
Cold Fusion ◽  
Entrance Channel ◽  
Superheavy Nuclei ◽  
Fusion Reactions

Dynamical model for neck formation in the entrance channel of a heavy ion collision

1982 ◽  
Vol 306 (4) ◽  
pp. 307-313 ◽  
Author(s):  
S. K. Samaddar ◽  
B. C. Samanta ◽  
D. Sperber ◽  
M. Zielińska-Pfabé
Keyword(s):  
Heavy Ion ◽  
Entrance Channel ◽  
Dynamical Model ◽  
Heavy Ion Collision ◽  
Neck Formation ◽  
Ion Collision

scholarly journals The pre-equilibrium and equilibrium double differential cross sections for the nucleons and light nuclei induce nuclear reactions on 27Al nuclei

2019 ◽  
Vol 15 (32) ◽  
pp. 77-91
Author(s):  
Maha Taha Idrees
Keyword(s):  
Cross Sections ◽  
Differential Cross ◽  
Nuclear Reactions ◽  
State Density ◽  
Light Nuclei ◽  
Hole State ◽  
Differential Cross Sections ◽  
Mass System ◽  
Shell Effects ◽  
27Al Target

The pre - equilibrium and equilibrium double differential crosssections are calculated at different energies using Kalbach Systematicapproach in terms of Exciton model with Feshbach, Kerman andKoonin (FKK) statistical theory. The angular distribution of nucleonsand light nuclei on 27Al target nuclei, at emission energy in the centerof mass system, are considered, using the Multistep Compound(MSC) and Multistep Direct (MSD) reactions. The two-componentexciton model with different corrections have been implemented incalculating the particle-hole state density towards calculating thetransition rates of the possible reactions and follow up the calculationthe differential cross-sections, that include MSC and MSD models.The finite well depth, isospin, shell effects, Pauli effect, chargeeffect, pairing, surface, angular and linear momentum distributionscorrections are considered in this work. The nucleons (n and p) andlight nuclei (2D and 3T) have been employed as projectiles at thetarget 27Al nuclei and at different incident energies (4MeV, 14 MeVand 14.8MeV). The results have been compared with the availableexperimental and theoretical published work. The comparisons showan acceptable agreement with the TALAYS code (Tendel 2014) forthe reactions: 27Al (n, n) 27Al, 27Al (p, n) 63Zn, 27Al (p, D) 62Cu, 27Al(p, p) 63Cu and 27Al (p, 4He)60Ni and at different emission energiesand angles.

Investigation of the synthesis of the unknown superheavy nuclei 309,312126

2019 ◽  
Vol 28 (07) ◽  
pp. 1950056 ◽  
Author(s):  
T. V. Nhan Hao ◽  
N. N. Duy ◽  
K. Y. Chae ◽  
N. Quang Hung ◽  
N. Nhu Le
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Charge Asymmetry ◽  
Evaporation Residue ◽  
Fission Process ◽  
Dinuclear System ◽  
Mass Asymmetry ◽  
Interacting Systems ◽  
First Time ◽  
Text Element

In this paper, we applied the method developed by Santhosh and Safoora in [Phys. Rev. C  94 (2016) 024623; 95 (2017) 064611] to theoretically investigate the fusion, evaporation-residue (ER) and fission cross-sections of the synthesis of the unknown superheavy [Formula: see text]126 nuclei produced by using the [Formula: see text]Ni + [Formula: see text]Cf and [Formula: see text]Zn + [Formula: see text]Cm combinations. The charge asymmetry, mass asymmetry and fissility of the DiNuclear System (DNS) in the synthesis of the mentioned combinations are also estimated. The calculated results show that the ER cross-sections for the synthesis of the [Formula: see text]126 nuclei are predicted to be much less than 1.0[Formula: see text]fb. In particular, it has been found that there may exist a valley of the ER cross-sections in the synthesis of a superheavy [Formula: see text] element, which produces the [Formula: see text]126 isotope. Subsequently, a model for the mass dependence of the ER cross-section in the synthesis of the [Formula: see text]126 isotopes has been proposed for the first time. On the other hand, the quasi-fission process strongly dominates over the fusion in the two concerned interacting systems. The present results, together with those reported in the previous studies, indicate that the investigated projectile–target combinations are not capable for the synthesis of the [Formula: see text]126 isotopes due to tiny fusion cross-sections (about 2–3[Formula: see text]zb), which go beyond the limitations of available facilities. Further studies are thus recommended to search for alternative interacting systems. In conclusion, this work provides useful information for the synthesis of the gap isotopes [Formula: see text]126, which have not been well studied up to date.

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