Fission of super-heavy nuclei: Fragment mass distributions and their dependence on excitation energy
Abstract
The mass and total kinetic energy distributions of the fission fragments in the fission of even-even isotopes of superheavy elements from Hs (Z=108) to Og (Z=118) are estimated using a pre-scission point model. We restrict to nuclei for which spontaneous fission has been experimentally observed. The potential energy surfaces are calculated with Strutinsky’s shell correction procedure. The parametrization of the nuclear shapes is based on Cassini ovals. For the just before scission configuration we fix α = 0.98 , what corresponds to rneck ≈ 2 fm, and take into account another four deformation parameters: α1 , α1 , α4 , α6 . The fragment-mass distributions are estimated supposing they are due to thermal fluctuations in the mass asymmetry degree of freedom just before scission. The influence of the excitation energy of the fissioning system on these distributions is studied. The distributions of the total kinetic energy (TKE) of the fragments are also calculated (in the point-charge approximation). In Hs, Ds and Cn isotopes a transition from symmetric to asymmetric fission is predicted with increasing neutron number N (at N ≈ 168). Super-symmetric fission ocurs at N ≈ 160. When the excitation energy increases from 0 to 30 MeV, the peaks (one or two) of the mass distributions become only slightly wider. The first two moments of the TKE distributions are displayed as a function of the mass number A of the fissioning nucleus. A slow decrease of the average energy and a minimum of the width (at N ≈ 162) is found.
Keywords
About the Authors
N. .. CarjanRussian Federation
F. A. Ivanyuk
Romania
Yu. Ts. Oganessian
Russian Federation
References
1. S. Dmitriev et al., EPJ Web of Conferences 131 (2016) 08001.
2. D.J. Hinde et al., EPJ Web of Conferences 66 (2014) 03037.
3. K. Nishio, EPJ Web of Conferences 62 (2013) 03001.
4. N. Carjan et al., Nucl. Phys. A 942 (2015) 97.
5. N. Carjan et al., J. Phys. Conf. Ser. 863 (2017) 012044.
6. N. Carjan et al., Nucl. Phys. A 968 (2017) 453.
7. M. Brack et al., Rev. Mod. Phys. 44 (1972) 320.
8. V.V. Pashkevich, Nucl. Phys. A 477 (1988) 1.
9. W. Norenberg, The Second Symposium on Physics and Chemistry of Fission, Vienna (1969) 51.
10. Yu. Oganessian, V. Utyonkov, Rep. Prog. Phys. 78 (2015) 036301.
11. Yu. Oganessian et al., Phys. Scr. 92 (2017) 023003.
12. F.-P. Hessberger, Eur. Phys. A 53 (2017) 75.
13. A. Svirikhin et al., AIP Conference Proceedings 1175 (2009) 297.
Review
For citations:
Carjan N..., Ivanyuk F.A., Oganessian Yu.T. Fission of super-heavy nuclei: Fragment mass distributions and their dependence on excitation energy. Eurasian Journal of Physics and Functional Materials. 2019;3(1):10-17. https://doi.org/10.29317/ejpfm.2019030101