Narrow Results

Most of the decaying systems namely α-decay and proton radio activity have extremely narrow widths and hence are termed as quasi-bound states. There are three methods available for the computation of very narrow widths. First, the analytic S-matrix method which treats resonance as a pole in complex energy plane with its real part representing resonance energy and the imaginary part the half width. Another two methods namely (i) direct (D) method and (ii) distorted wave (DW) method are based on the property of the quasi-bound state wave function which is quite similar to a bound state wave function in the interior region and is matched with an outgoing spherical wave representing decaying behavior. We make a comparative study of these methods by applying them to the α-decay systems whose experimental results of Q-value and decay half-lives are known recently. It is observed that all the three methods give practically the same results for widths calculated at the same Q-value and explain the experimental results of Q-values and half-lives in several α-decaying nuclei quite well with a proper Coulomb nuclear interaction potential for the α+daughter nucleus system.

The importance of measuring Q-values in rapid proton capture process has been investigated. The microscopic optical model, derived using a nucleon–nucleon interaction and densities from relativistic mean field (RMF) calculations, has been utilized to calculate the reaction rates. It has been observed that the Q-values involved in the reactions at waiting points at A = 60 and 64 are very important in determining the final abundance of the process. Some other Q-values also play a crucial role in the final abundance of nuclei near the end point of the process.

Cluster radioactivity is a rare cold nuclear process which is intermediate between alpha decay and spontaneous fission. The present work is a theoretical investigation of the feasibility of alpha decay and cluster radioactivity from proton rich Osmium (Os) isotopes with mass number ranging from 162–190. Osmium forms a part of the transition region between highly deformed and spherical nuclei. Calculations have been done using unified fission model and Hartree–Fock–Bogoliubov (HFB) theory. We have chosen only those decays with half-lives falling in measurable range. Geiger–Nuttall plot has been successfully reproduced. The isotope which is most favorable to each decay mode has a magic daughter nucleus.

The $\alpha$-decay and spontaneous fission (SF) half-lives for even–even isotopes of superheavy nuclei in the range $106\le Z\le 124$ are predicted using nuclear double-folding and Coulomb potentials. The $\alpha$-decay half-lives are computed based on WKB approximation for tunneling probability through potential barrier. The half-lives of SF have also been calculated using a semi-empirical relation constructed by Santhosh et al. [Nucl. Phys. A832, 220 (2009)]. Our calculated half-lives of cold SF and $\alpha$-decay are compared with the available experimental data. This comparison indicates that our obtained half-lives are in good agreement with the available experimental data. The competition between $\alpha$-decay and SF is also analyzed in detail and the decay modes are predicted for the unknown cases. Variation of $\alpha$-decay and SF half-lives with mass number of the parent isotopes for each nucleus revealed the major role played with shell effect.

The feasibility of alpha and cluster decay from Pt isotopes has been investigated within the framework of Skyrme Hartree–Fock–Bogoliubov (HFB) theory. Calculations have been carried out for various Skyrme forces. Harmonic oscillator and transformed harmonic oscillator basis are used to solve HFB equations. The role played by shell closure is analyzed. Half-lives are estimated with the help of Universal Decay Law (UDL). Geiger–Nuttal plots are also drawn and their linear nature is successfully reproduced.

In this paper, Isotopic yield and half-lives of cold spontaneous fission for ${}^{279}Ds$ and ${}^{281}Ds$ superheavy isotopes are studied. The interacting potential between fragments includes mean field proximity and Coulomb potentials. Fission $Q$-value, driving potential, $(V(r)-Q)$ and partial penetration probability of each possible individual fragmentation are calculated using $WKB$ approximation. According to the tunneling effect, the most favored pair of fragments is produced for the highest $Q$-value or the lowest driving potential. A few fragmentation with higher $Q$-value are selected for each atomic number Z. It is found that for ${}^{279}Ds$ isotope, the highest relative yield belongs to the ${}^{134}$Te + ${}^{145}$Ce fragmentation while for ${}^{281}Ds$, the combination ${}^{134}$Te + ${}^{137}$Ce has lowest driving potential and highest yield due to presence of fragments with magic or near magic proton and neutron numbers ($Z=50$ and $N=82$). By calculating yield of each fragmentation, its partial fission decay constant and then by summing over all decay constants for possible fragmentation, the fission decay constant for each superheavy isotope is obtained. Furthermore, half-life of each superheavy isotope is also estimated. Finally, the calculated half-lives using this method are compared with the experimental data. Good agreement achieved between our calculated half-lives and the experimental data.

In this paper, $\alpha$-decay half-life of axially symmetric deformed even–even isotopes with atomic numbers $88\le Z\le 104$ had been studied for the transition between the ground states of the parent and daughter nuclei. Quadrupole deformation of daughter nuclei (if any) is considered in calculations. The interaction between the $\alpha$-particle and daughter nucleus includes the nuclear double-folding, the Coulomb and rotational terms. Wang’s formula is used for coulomb interaction between spherical $\alpha$-particle and deformed daughter nucleus. The Q-value of $\alpha$-decay is calculated and used to obtain its half-life, based on the WKB approximation for the penetration probability of $\alpha$-particle through the potential barrier. A Q-value-related formula is used to estimate the $\alpha$-particle preformation factor. The calculated $\alpha$-decay half-lives are compared with the available experimental data. The standard deviation between computed results and experimental data is obtained equal to 0.288. Comparison of our obtained standard deviation indicates well the validity of our chosen theoretical model. Furthermore, the characteristic of $\alpha$-decay energy and half-lives confirms the shell effects at $N=126$ magic number. Also, the obtained results predict similar closed shells behavior at $N=152$ and $N=162$ neutron numbers.