Narrow Results

In this study, we calculate the fission properties of superheavy elements within the mass range $253\le A\le 294$ using the Coulomb and Proximity Potential Model (CPPM) and the Modified Generalized Liquid Drop Model (MGLDM). A systematic comparison of possible decay modes, including $\alpha$-decay and Spontaneous Fission (SF), is conducted for the isotopic chain of superheavy nuclei (SHN) under investigation. The calculated $\alpha$-decay half-lives using both models show excellent agreement with available experimental data. Moreover, the comparison of $\alpha$-decay and SF half-lives successfully reproduces the observed experimental decay modes, demonstrating that CPPM and MGLDM are highly efficient and accurate frameworks for exploring the decay properties of SHN.

Due to the quantum nature of $\alpha$-decay, the WKB approximation is an indispensable tool for calculating the barrier penetration probability. In this study, $\alpha$-decay half-lives of 398 nuclei are calculated using a simple semi-empirical model based on Gamow theory. Calculation of $\alpha$-decay half-lives, barrier penetrability, assault frequency and preformation probability were performed for 252 nuclei with $Z=52$ to 99 and for 146 super-heavy nuclei with $Z=100$ to 120. The obtained results are tested against the available experimental data and some well-known empirical formulas. A very good agreement with the experiment is achieved in both cases. Our results align well with the closed-shell effects at neutron magic numbers $N=126$ and 152. Moreover, a clear correlation between the experimental decay half-lives and the calculated penetration probabilities is obtained.

The second 2⁺ state in the 10 MeV region of ¹²C was investigated by measuring decay-α particles in the ¹²C nucleus excited by inelastic α scattering at 0°. Angular correlation functions were obtained at backward angles from 115° to 255°. Those for 9.64 MeV 3^-, 15.4 MeV 2⁺, and 18.2 MeV 2⁺ states were good agreement with the PWBA calculation. The third 0⁺ state was also investigated. The coincidence spectra at 245° of decay-α particles seem to be consisted of two 0⁺ components.

The ⁸Be nucleus decays into two ⁴He nuclei. This decay constant is theoretically estimated using Fermi golden rule and the ground state wave functions of the ⁴He and ⁸Be nuclei. The estimated result agrees pretty well with the reported experimental value.

Employing the effective liquid drop model (ELDM), half-lives of proton and alpha decays and probable cluster decays are computed and analyzed for different proton-rich and neutron-rich isotopes of Rhenium. The investigation fortifies the phenomenon of cluster radioactivity (CR) in rare earth nuclei and also affirms the pivotal role played by neutron magicity in cluster decays. ELDM data is compared with that of universal decay law (UDL) model and found to be more efficient than the latter one. Apparently, cluster emissions slacken as the neutron number of daughter nucleus goes up and the linear nature of Geiger–Nuttall (G–N) plots stays unaltered even if the surface potential is incorporated.

By using WKB method and considering deformed Woods–Saxon nuclear potential, deformed Coulomb potential, and centrifugal potential, the alpha decay half-lives of 68 superheavy alpha emitters have been calculated. The effect of the constant value of surface diffuseness parameter in the range of 0.1 $\le$a$\le$ 0.9 (fm) on the potential barrier, tunneling probability, assault frequency, and alpha decay half-lives has been investigated. Significant differences were observed for alpha decay half-lives and decay quantities in this range of surface diffuseness. Good agreement between calculated half-lives with fitted surface diffuseness parameter a = 0.54 (fm) and experiment was observed.

We have formulated a semi-empirical formula for alpha decay half-lives and cluster decay half-lives for superheavy nuclei of atomic number range $104\le Z\le 130$. We have compared the logarithmic half-lives produced by the present formula with that of experiments and other formulae, such as universal decay law (UDL) [H. C. Manjunatha and K. N. Sridhar, Eur. Phys. J. A53, 156 (2017)] and Horoi et al. [Horoi et al., J. Phys. G$:$ Nucl. Part. Phys.30, 945 (2004)], Univ [D. Ni and Z. Ren, Phys. Rev. C74, 014304 (2006)], Royer [G. Royer, J. Phys. G: Nucl. Part. Phys.26, 1149 (2000)] and VSS [S. A. Gurvitz and G. Kalbermann, Phys. Rev. Lett.59, 262 (1987)]. The constructed formula produces logarithmic half-lives for alpha and cluster decay (⁴He,⁹Be, ${}^{10,11}$B, ${}^{12}$C, ${}^{14}$N, ${}^{16}$O, ${}^{19}$F, ${}^{20-22}$Ne, ${}^{23}$Na, ${}^{24-26}$Mg, ${}^{27}$Al, ${}^{28-30}$Si, ${}^{31}$P, ${}^{32-34}$S, ${}^{35}$Cl, ${}^{36,38,40}$Ar, ${}^{39,41}$K and ${}^{40,42-44,46}$Ca) in superheavy nuclei of atomic number range $104\le Z\le 130$.

A simple, semi-empirical, one-parameter calculation model based on the quantum mechanical tunneling mechanism through a potential barrier has been used to estimate the partial $\alpha$-decay half-life, $T_{1/2}^{\alpha }$, of ${}^{178}{\mathrm{\text{Hf}}}^{m2}$ isomer. Alpha-transitions to levels of the ground-state band $J^{\pi }=0^{+},2^{+},\dots ,14^{+}$ of ${}^{174}\mathrm{\text{Yb}}$ have been considered, and the contributions to $T_{1/2}^{\alpha }$ due to overlapping, Coulomb, and centrifugal barriers have been detailed in each case. Results have indicated a $T_{1/2}^{\alpha }$-value of $(0.24\pm 0.07)\mathrm{\text{Gyr}}$ and a predominance $(\sim 57\%)$ of $\alpha$-particles populating the level $J^{\pi }=6^{+},E_{\gamma }=526\mathrm{\text{keV}}$, compatible with results by other authors. Besides, a single, universal-like formula to estimate half-life of alpha transitions, whatever $\ell$-value and the characteristics of the parent nucleus (e-e, e-o, o-e and o-o nuclei, whether in the ground or isomeric states), has been envisaged.

A physical model that can quantitatively describe the spontaneous alpha-particle emission mechanism from atomic nuclei in the spherical nucleus approximation has been applied to the evaluation of the half-life of the ${}^{146}$Sm nuclide. The one-parameter, semi-empirical model used in this study has been developed in the frame of a quantum mechanical mechanism of alpha tunnelling through a potential barrier, taking into account centrifugal and overlapping effects. The calculation procedure yielded a value of $145.1\pm 0.3$Myr for the half-life of the extinct ${}^{146}$Sm isotope. This value, even if in disagreement with the few old measurements performed on the artificially obtained ${}^{146}$Sm, is thought to represent the most reliable indication of the $\alpha$-decay rate for such challenging nuclide.

We studied the alpha decay half-life of Americium isotopes ($\mathrm{\text{Z}}=95$) with mass numbers ranging from 223 to 243. Our investigation employed the Coulomb and proximity potential model (CPPM), in addition to alternative analytical and semiempirical formulas. The calculations took into account both experimental and theoretical Q-values, as well as the total alpha kinetic energy. We analyzed the behavior of the hindrance factor concerning changes in the mass numbers of parent nuclei within the range of 223–243, and also examined the impact of magic numbers associated with closed shells. To evaluate the accuracy of our findings, we utilized the SemFIS, UNIV, and Royer formulas to make predictions, which were then compared to the existing experimental data.

Development of low radioactive technique allows to investigate many other rare nuclear and subnuclear processes: double $\beta$ decay, rare $\beta$ and $\alpha$ decays, and to search for hypothetical particles and processes like axions, charge nonconserving decays, the nucleon, di-nucleon and tri-nucleon decays into invisible channels, to test the Pauli principle. Here, we present results of the rare processes searches and development of instrumentation for low counting experiments.

The DAMA project has obtained many competitive or new results in the search for various rare nuclear processes. Most of them have been obtained with the help of many different high purity crystal scintillators which have been measured in the low-background DAMA set-ups located in the Gran Sasso underground laboratory of INFN In this paper, the main results will be summarized.

Recently, long-lived high spin super- and hyperdeformed isomeric states with unusual radioactive decay properties have been discovered. Based on these newly observed modes of radioactive decay, consistent interpretations are suggested for previously unexplained phenomena seen in nature. These are the Po halos, the low-energy enhanced 4.5 MeV α-particle group proposed to be due to an isotope of a superheavy element with Z=108, and the giant halos.

A comparative study of the S-matrix and the WKB methods for the calculation of the half widths of alpha decay of super heavy elements is presented. The extent of the reliability of the WKB methods is demonstrated through simple illustrative examples. Detailed calculations have been carried out using the microscopic alpha-daughter potentials generated in the framework of the double-folding model using densities obtained in the relativistic mean field theories. We consider alpha-nucleus systems appearing in the decay chains of super heavy parent elements having A = 277, Z = 112 and A = 269, Z = 110. For negative and small positive log τ_1/2 values the results from both methods are similar even though the S-matrix results should be considered to be more accurate. However, when log τ_1/2 values are large and positive, the width associated with such state is infinitesimally small and hence calculation of such width by the S-matrix pole search method becomes a numerically difficult problem. We find that overall, the WKB method is reliable for the calculation of half lives of alpha decay from heavy nuclei.

In the framework of the generalized liquid drop model (GLDM) and improved Royer's formula, we investigate the branching ratios and half-lives of α-decay to the members of the ground-state rotational bands of heavy even–even Fm and No isotopes. The calculated results are in good agreement with the available experimental data and some useful predictions are provided for future experiments.

In the framework of the generalized liquid drop model (GLDM) and improved Royer's formula with a set of new coefficients derived by N. D. Schubert et al. [Eur. Phys. J. A42 (2009) 121], the favored and unfavored α-decay half-lives of exotic nuclei around closed shells Z = 82 and N = 126 are investigated. The calculated results are in good agreement with the experimental data. It is shown that our method can be used to study the α-decay half-lives of exotic nuclei around shell closures successfully and is helpful for future research on superheavy nuclei around the next proton and neutron shell closures. In addition, some α-decay half-lives for the cases where the experimental values are unavailable are predicted. We hope our predicted results are useful for future experiments.

Calculations of half-lives of superheavy nuclei (SH) show an unexpected result: For some of them heavy particle radioactivity (HPR) dominates over α decay (branching ratios larger than 1). The new mass table AME11 and the theoretical KTUY05 and FRDM95 masses are used to determine Q-values. For Z = 124 we found isotopes with half-lives in the range of ns to ps.

We intend to study the half-lives of Bismuth isotopes via the alpha decay process. To go through the problem, we consider a potential model in which an angle-dependence is considered. Our results reveal that taking into account the multipole approximations for both parent and daughter nuclei will improve the results.

We study the half-lives of some Pt isotopes via the alpha-decay process and a modified barrier penetration formula different from the traditional barrier potentials. Comparison with the existing data is quite motivating.

In this study, the nuclear decay equation is taken under consideration by making use of fractional calculus. In this context, the first-order time derivative is changed to a Caputo fractional derivative hence, the resulting equation is the time fractional nuclear decay equation. The solution of this equation is obtained in terms of Mittag–Leffler function which plays an important role to study the non-Markovian feature of physical processes. As an application of this time fractional formalism, alpha decay half-life values have been calculated for Pb, Po, Rn, Ra, Th and U isotopes. Consequently, the theoretical half-life values have been obtained in consistent with the experimental data. The dependence of the order of fractional derivative μ being a measure of fractality of time, on the nuclear structure has been established. In the investigations carried out, we have arrived to the conclusion that for the μ values which are closed to one, where time becomes homogenous and continuous, the shell closure effects are predominant and that the fractional derivative order μ (i.e., fractality of time) and nuclear structure are closely related to each other.