Proceedings of the DAE Symp. on Nucl. Phys. 64 (2019) 180

Dominant decay modes of SHN Z = 118 − 130 G. Naveya1, S. Santhosh Kumar2, A. Stephen1,∗ and S.I.A. Philominraj3 1Department of , University of Madras, Guindy Campus, Chennai-600025, INDIA 2Department of Physics, Kanchi Mamunivar Centre for Post Graduate Studies, Lawspet, Puducherry-605008, U. T. of Puducherry, INDIA and 3Department of Physics, Madras Christian College, Chennai-600059,INDIA

Introduction Theoretical Framework In decay process the parent nuclei get split into daughter and fragment nuclei. The post- scission region potential is V (r) = V (r) + The study on superheavy nuclei (Z>104) ext n V (r)+V (r). The nuclear interaction between has remained an important area of research in c l daughter and fragment proximity potential is modern nuclear physics. In last four decades, described as [5], theoretical studies have suggested shell closure and shell closure beyond Z=82 C1C2 and N=126 in the superheavy region is at Vn(r) = 4πγb φ(s). Z=114 and N=184, and it is expected that C1 + C2 around this doubly magic nuclei will We have considered pre-scission potential as a form an [1]. The superheavy cubic potential [6]. The tunneling probability elements with Z=107-112 have been success- is obtained using improved transfer matrix fully synthesized at GSI, Darmstadt. Isotopes method [7]. In the barrier region the of these elements along with Z=113-116 and wavefunction in barrier region is considered 118 have been synthesized at JINR-FLNR, as plane wave and at the boundaries WKB Dubna and Z=110-113 have been produced wavefunction is most suited. The tunneling at RIKEN, Japan [2]. The SHN synthesized probability and half-life calculations are as in laboratory decay mainly via alpha emission described in Ref.[4]. For the present study, we and spontaneous fission, but can also undergo have used the WS-4 binding energy data as it proton decay for a range of mass numbers and provides good description of nuclear masses in there exists a possibility of heavy cluster decay heavy and superheavy region [8]. from SHN. The , the , and the cluster decay can be explained using quantum tunneling phenomena. The Result and Discussion decay studies are important, as it brings The peaks obtained in alpha decay half-life out the degree of stability of nuclei with plot of Z=118 (fig. 1) suggest that some different proton and neutron numbers, and isotopes are relatively more stable than gives information about possible decay modes neighbouring ones, which to neutron and . There is abundance magic/semi-magic numbers at N=178, 184, of literature on the lifetime and stability of 196, 200, 220 & 228 which coincides well with SHN upto Z=130 [3]. In this work, we Ismail et al [9]. In fig. 2 the competition study the dominant decay mode of Z=118-130 between various decay modes of Z=118 isotopes using recently developed Cubic Plus such as proton decay, alpha decay and Proximity model [4]. spontaneous fission half-lives are plotted for the isotopes, and the dashed lines indicate the current experimental detection limits −6 30 10 s ≤ T1/2 ≤ 10 s. ∗Electronic address: [email protected]

Available online at www.sympnp.org/proceedings Proceedings of the DAE Symp. on Nucl. Phys. 64 (2019) 181

40 fig. 2 determines that A < 304 is α - decay 4 Z=118 possible nuclei and A> 304 will follow SF. 32 2He The dominant decay modes for Z=118-130 is 24 presented in table 1. These results brings 16 out the possible decay modes associated with

1/2 isotopes of SHN Z = 118 − 130, and may help 8 experimentalist in identifying the isotopes to LogT 0 be synthesized in laboratories in the future. -8

-16 TABLE I: Prediction of dominant decay modes -24 for Z=118-130 isotopes 160 170 180 190 200 210 220 230 240 Parent Region of dominating decay modes Parent Nuclei Neutron Number Z 1p α SF

FIG. 1: The alpha decay half life of Z = 118 118 - 280 ≤ A ≤ 302 304 ≤ A ≤ 350 isotopes 120 - 284 ≤ A ≤ 308 310 ≤ A ≤ 350

100 122 - 290 ≤ A ≤ 314 316 ≤ A ≤ 350 α SF 1p 80 124 - 296 ≤ A ≤ 320 322 ≤ A ≤ 350 60 Z=118 126 - 302 ≤ A ≤ 328 330 ≤ A ≤ 350 40 128 - 308 ≤ A ≤ 334 336 ≤ A ≤ 350 1/2 20 130 - 316 ≤ A ≤ 342 344 ≤ A ≤ 350

LogT 0 -20 References -40 [1] Y. T. Oganessian et al., Nucl. Phys. A 734 -60 (2004) 109. 270 280 290 300 310 320 330 340 350 [2] S. Hofmann, in New Horizons in Funda- of Parent Nuclei mental Physics, Springer, Cham (2017). [3] S. Santhosh Kumar et al., Proc. DAE FIG. 2: Competition between decay modes of Z = Symp. Nucl. Phys. 60 (2015) 486. 118 [4] G. Naveya et al., Int. J. Mod. Phys. E 28 (2019) 1950051. Investigation of competition between var- [5] J. Bocki et al., Ann. Phys. 105 (1977) 427. ious decay modes brings out the dominant [6] G. Shanmugam and B. Kamalaharan, decay mode associated with an ; for a Phys. Rev. C 38 (1988) 1377. given Z with increasing A the dominant mode [7] D. Biswas and V. Kumar, Phys. Rev. E 90 of decay is seen to shift from proton decay to (2014) 01330. alpha decay and finally spontaneous fission. [8] N. Wang et al., Phys. Lett. B 734 (2014) It is well noticed from fig. 2 that emission 215. of proton from Z=118 is not a possible decay [9] M. Ismail et al., Ann. Phys. (2019) Doi: mode. The converging point at A=304 in 10.1016/j.aop.2019.03.020.

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