α-decay half-lives of the observed superheavy nuclei(Z=108−118)

Abstract

A systematic and comprehensive study of the decay half-lives of nuclei appearing in the observed α-decay chains of superheavy elements (Z = 108−118) is presented. The calculation proceeds in three steps. First, the relativistic mean-field equations are solved in the axially symmetric deformed oscillator basis to obtain ground-state properties such as binding energies, radii, deformations, and densities. The results are in good agreement with the available experimental systematics, as expected. Next, the calculated densities are used in the double-folding prescription to determine the interaction potentials for the α-daughter systems. Finally, these potentials, along with calculated and experimental Q values, are used in the WKB approximation to estimate the decay half-lives. The calculated half-lives, which sensitively depend on Q values, qualitatively reproduce the experiment. The production and study of superheavy elements (SHE) has been the cherished aim of experimentalists since the prediction of the island of stability, around Z ∼ 114, N ∼ 184 in the 1960s. It has still not been possible to reach the N = 184 closed shell. Earlier experiments had partial success. Cold (hot) fusion with Pb/Bi (actinides: 235 U / 244 Pu / 243 Am) targets and suitable projectiles of 64 Ni / 70 Zn ( 48 Ca) have been successfully used for the production of superheavy elements 110−113 (114−116). The search for isotopes of these elements and also for elements with higher atomic numbers (Z ) is pursued vigorously by a number of laboratories around the world.On the theoretical front, primarily two kinds of approaches have been used to describe superheavy nuclei: microscopic theories and microscopic-macroscopic models. The relativistic mean-field (RMF) theory [1,2] belongs to the former, and the Möller-Nix [3] or the Muntian [4] models are examples from the latter category. The aim of the earlier RMF studies [5] had been to predict the most stable N and Z combination. In self-consistent models, the occurrence of a spherical proton (neutron) shell closure with given Z (N ) may change with varying neutron number N (Z ). Such systematic investigations are still being reported [6][7][8]. A number of RMF investigations for the ground-state properties of nuclei appearing in the observed decay chains of specific superheavy nuclei have also been reported (e.g., [9][10][11]). The calculated binding energies reproduce Audi-Wapstra systematics [12] rather well. However, most of these use the phenomenological ViolaSeaborg formula [13] for the calculation of the decay halflives. Our emphasis in this Brief Report is on microscopic calculation of the α-decay half-lives, where the experimental data are available [14][15][16][17][18][19]. First, the ground-state properties are calculated in the RMF framework. We do not intend to present all the details of the ground-state properties; instead, we list essentials of the emerging systematic features, which are consistent with earlier investigations. The present * Electronic address: yogy@phy.iitb.ac.in.c...

Theoretical description of superheavy nuclei

“…Refs. [43,56,68,72,73,76,[80][81][82]). In the analysis of the decay chains, however, effects of the single-particle structure of the nuclei have been usually disregarded.…”

“…[59][60][61][62][63][64][65][66][67] and theoretical ones (e.g. [29,56,[68][69][70][71][72][73][74][75][76][77][78][79]). For SHN, this is almost exclusively the α spectroscopy.…”

Erratum: α-nucleus potentials, α-decay half-lives, and shell closures for superheavy nuclei [Phys. Rev. C73, 031301(R) (2006)]

“…The calculated α-decay half-lives remain far below one nanosecond for superheavy nuclei with double shell closure and masses above A > 300 independent of the precise knowledge of the magic proton and neutron numbers. The α-decay of superheavy nuclei has been studied intensively in the last years [1,2,3,4,5,6,7,8,9,10]. In many papers a simple two-body model was applied [11], and in most papers a potential was derived which was able to fit the measured α-decay half-lives of the analyzed nuclei.…”

Potential for α -induced nuclear scattering, reaction and decay, and a resonance-pole-decay model with exact explicit analytical solutions

“…The process of decay of alpha (α) particle from heavy and super-heavy nuclei has been studied intensively in the past few years [1][2][3][4][5][6][7][8][9][10][11][12]. In many papers a simple two-body model was applied [11][12][13] and in most papers a potential was derived that was able to fit the measured α-decay half-lives of the alpha emitters.…”

“…In many papers a simple two-body model was applied [11][12][13] and in most papers a potential was derived that was able to fit the measured α-decay half-lives of the alpha emitters. In recent time, such a potential for the α+nucleus two-body interaction is generated microscopically in the double folding (tρρ approximation) using explicitly the nuclear (both proton and neutron) densities [4,14].…”