Recent α decay half-lives and analytic expression predictions including superheavy nuclei

Abstract

New recent experimental α-decay half-lives have been compared with the results obtained from previously proposed formulae depending only on the mass and charge numbers of the α emitter and the Qα value. For the heaviest nuclei they are also compared with calculations using the DensityDependent M3Y (DDM3Y) effective interaction and the Viola-Seaborg-Sobiczewski (VSS) formulae. The correct agreement allows to provide predictions for the α decay half-lives of other still unknown superheavy nuclei from these analytic formulae using the extrapolated Qα of Audi, Wapstra The α decay process was described in 1928 [2,3] in terms of a quantum tunnelling through the potential barrier separating the mother nucleus energy and the total energy of the separated α particle and daughter nucleus. To describe the α emission two different approaches have been developed. The cluster-like theories suppose that the α particle is preformed in the nucleus with a certain preformation factor while the fission-like approaches consider that the α particle is formed progressively during the very asymmetric fission of the parent nucleus. The experimental investigation cannot unambiguously distinguish these two formation modes. However the possible one-body configurations play a minor role since in the quasi-molecular decay path investigated in the α decay process the potential barrier is governed by the balance between the repulsive Coulomb forces and the attractive proximity forces and the Q α value; consequently the barrier top is more external and lower than the pure Coulomb barrier and corresponds to two separated fragments. The difference between the two approaches appears mainly in the way the decay constant is determined. In the unified fission models [4,5] the decay constant λ is the product of the constant assault frequency ν 0 and the barrier penetrability P while in the preformed cluster models [6,7] a third factor is introduced : the cluster preformation probability P 0 .Before the theoretical explanation and description of the α decay process, Geiger and Nuttal [8] observed a dependence of the α decay partial half-life T expt 1/2,α on the mean α particle range for a fixed radioactive family and Geiger-Nuttal plots are now an expression of log 10 T α as a function of ZQ −1/2 . Since, different new relations have been proposed [5,9,10,11,12,13] to calculate log 10 T α from the measured kinetic energy of the α particle via [14,15,16,17,18,19,20]. These recent experimental results have led to new theoretical studies on the α decay; for example within the relativistic mean field theory [21], the DDM3Y interaction [22,23], the generalized liquid drop model (GLDM) [24,25] and SkyrmeHartree-Fock mean-field model [26]. The predicted halflives against α decay of these transuranium nuclei obtained with a semiempirical formula taking into account the magic numbers have also been compared with the analytical superasymmetric fission model results and the universal curves and the experimental data [13].In previous studies [5,27] both theoretic...

Isospin asymmetry dependence of theαspectroscopic factor for heavy nuclei

“…The experimental data are taken from Refs. [13,14,21,[60][61][62][63] Table I. proton holes in addition to the valence protons or neutrons, then the spectroscopic factor decreases with increasing the isospin asymmetry. For example, for the presented nuclei with N p N n = −16, the spectroscopic factor starting from S α = 0.048(0.070) for 158 W(I = 0.063) goes down to S α = 0.030(0.050) for 208 Rn(I = 0.173).…”

α-Decay Half-Lives for Pb Isotopes Within Gamow-Like Model

“…Royer empirical formula (Royer) Royer predicted new formula for alpha decay half-lives [12,[22][23] by fitting 373 nuclei which have transition from ground-state to ground state.…”

“…In this study we calculated the alpha decay decay half-lives for Pb isotopes using Gamow-Like Model (GLM), we compared the results with CPPM theoretical model [11] and with experimental data. Also we used some empirical formula to calculate alpha decay half-lives and to compare with GLD, like Royer formula [12], Universal Decay Low (UDL) [13], Viola-Seaborg formula (VSS) [14], Semi-empirical formula for Poenaru et. Al.…”

Theoretical Studies on the α-decay Half-Lives of Even-Even Lv Isotopes

“…The α-decay half-lives have been studied by using Royer formula [12,[22][23], Royer developed formula by fitting procedure using 373 nuclei transition from ground state to ground state which is given as…”

“…al also studied α-decay half-lives by considering a potential model with Yukawa proximity potential from ground state to ground state [10]. The aim of this work is to determine the α-decay half-lives of even-even Lv isotopes within Gamow-Like Model (GLM) and to compared with another theoretical model such as CPPM [11], Royer formula [12], Universal Decay Low (UDL) [13], Viola-Seaborg formula (VSS) [14], Semi-empirical formula for Poenaru et. Al.…”