Narrow Results

We illustrate wavefunctions and half-lives of α-radioactive even-A thorium isotopes based on the simple semi-classical theory of alpha-decay process. The potential is assumed to take an attractive square-well form inside the potential barrier and to take a repulsive Coulomb one outside the barrier. Overall for the even-A thorium isotopes, only two parameters r₀=1.14 fm and V₀=16 MeV are used. Outside the region of a potential barrier, an obvious oscillating feature of wavefunction for ²¹⁸Th nucleus does not appear until the Q_α value is less than 20 MeV. Such a characteristic feature is confirmed by the three dimensional surface plot for the wave function of ²¹⁸Th nucleus. Our predicted values of half-life for even-A thorium isotopes are agreed satisfactorily with the observed results as a whole.

This paper investigates the persistency in the ex-post real interest rates in the presence of endogenous structural breaks for Australia, Austria, Belgium, Canada, Denmark, France, Germany, Ireland, Italy, the Netherlands, New Zealand, Norway, Switzerland, the UK and the USA using seasonally adjusted quarterly data. The procedure used in this study extends the previous research in the respect of investigating degree of persistency of the ex-post real interest rates series by allowing for possible process shifts at endogenously determined more than two structural breaks dates following the principles suggested by Lumsdaine and Papell (1997). The results from the study show that real interest rates are very persistent when such breaks are not taken into account. However, the findings also indicate low persistency in real interest rates for all countries when such breaks are allowed in the data-generating process. We find that endogenously determined structural breaks substantially reduce the degree of persistency of the real interest rate series, which has important theoretical implications as well.

The study examines the half-life deviations from purchasing power parity (PPP) using both linear and nonlinear models for the sector specific real exchange rates of the Pacific Rim countries. By using a linear benchmark model, the estimated half-life deviations from PPP of about/or less than 3 years seemingly solve the PPP puzzle. After re-examining them using nonlinear forms, the PPP puzzle for most sectoral real exchange rates in the study still remains. More specifically, we find that deviations from PPP by TAR are persistent and take much more time for mean reversions especially for non-tradable sectors using logistic STAR / exponential STAR (LSTAR/ESTAR). The major reasons might be that conventional studies have failed to control the possible nonlinearity of real exchange rates, and have disregarded the possible bias of any single numèraire country. Finally, we also show the speed of mean reversion for real exchange rates by sectoral prices (tradable and non-tradable).

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.

In this paper, we propose a new analytical solution of the $\alpha$-decay process for the Killingbeck potential with the spherical Coulomb potential and determine the half-lives of some $\alpha$-emitters with atomic number $(Z)$ located in the region $60\le Z\le 92$ using the Wentzel–Kramers–Brillouin (WKB) approximation. The Killingbeck potential, with its complex form including harmonic and linear confinement terms, offers a greater richness of interaction and nuclear shape. We provide a solution to the problem of multiple turning points by showing that they can be reduced to two nonsymmetric points. Results obtained show relationships between the paramater of the nuclear potential and experimental data. Those results are compared with experimental data and other theoretical results from the literature. We find that our results are in very good agreement with the experimental data.

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.

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 intend to study the alpha-decay half-lives of some nuclei from ground state to ground state. We consider a potential model with Yukawa proximity potential. We see that the results are in good agreement with the experimental data.

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 paper, the heavy cluster half-lives were calculated using the Wentzel–Kramers–Brillouin (WKB) method. First, we have considered the cluster and daughter nuclei as spherical and the half-lives have been obtained. Then, we have assumed two nuclei as deformed ones and calculations have been performed once again. Deformations of the emitted cluster and daughter nucleus have been presented in terms of elongation and neck thickness parameters. We investigated the influence of elongation and neck thickness parameters on cluster decay half-lives. Our results show that half-lives are affected by these parameters and obtained results for deformed nuclei are in better agreement with experimental data.

The half-lives of even–even nuclei with proton number Z ≥ 94 are calculated by proximity potential with a new universal function, especially for superheavy nuclei. The calculation results are compared to the experimental data. It is shown that from the presently obtained universal function, the calculated half-lives of α decay can basically keep agreement with the experimental data for most of even–even nuclei. Those of superheavy nuclei are also calculated and discussed.

Photonuclear reactions are important tools in the understanding of the nucleus. These reactions are also interesting for realizing the element creation processes in stellar environment. The use of bremsstrahlung photons generated from clinic linear accelerator is practical for performing these type of reactions. In this study, the bremsstrahlung photons with endpoint energy of 18MeV have been used for activating gallium target material. After irradiation, the transition energies and half-lives associated with the decay of ${}^{68}\mathrm{\text{Ga}}$, ${}^{70}\mathrm{\text{Ga}}$ and ${}^{72}\mathrm{\text{Ga}}$ isotopes have been determined The values obtained for half-life of ${}^{68}\mathrm{\text{Ga}}$, ${}^{70}\mathrm{\text{Ga}}$ and ${}^{72}\mathrm{\text{Ga}}$ isotopes are $67.5\pm 0.9$min, $21.1\pm 0.9$min and $13.8\pm 0.4$h, respectively. It has been seen that the values are consistent with the present literature values. In addition, the new measurements of gamma-ray energies for transition energies have been obtained comparable to the literature values with good uncertainties.

Photon induced reactions are called as photonuclear reactions and used in many research fields of nuclear science and nuclear physics. The photonuclear data are used in many nuclear applications such as radiation shielding and protection, radiation transport analyses, reactor core design, activation analysis and nuclear waste transmutation. In the past, many studies had been devoted to extract photonuclear data covering the isotopic chart. However, there is still lack of existing data. In the present study, we have performed photonuclear reactions on erbium (Er) target by using clinical electron linear accelerators (cLINAC). By using measured residual activity of photonuclear reaction products of Er nuclei, we have determined the half-life of ${}^{161}$Er nucleus and transition energies of ${}^{161}$Ho nucleus. Also, new measurements on gamma-ray energies of the products have been determined accurately. Furthermore, this study shows that repurposed cLINAC with limited budget can contribute to the global nuclear science knowledge.

The paper investigates the alpha-decay half-lives of some nuclei by modifying the Coulomb potential with Yukawa proximity potential for the excited state decays. A new relation is found for the width diffuseness of the nuclear surface $b_T$ and the sharp radii $R_{\mathrm{\text{i}}}$ for the excited system. The parameters are fitted to the experimental data for the nuclear temperature in the range $0\le T\le 1$ (MeV). A comparison of half-life indicates that the probability of decay increases with increasing nuclear temperature for the excited system. The comparison of the results with the existing experimental data is motivating.

We considered the systematics of Alpha-decay (AD) half-life (HL) of super-heavy nuclei (SHN) versus the decay energy and the total $\alpha$-kinetic energy. We have considered a potential model with Yukawa proximity potential and thereby calculated the HLs. Our results compared with experimental data and the empirical estimates. Also, we obtained $\alpha$-preformation factors from the ratio between theoretical and experimental results for a few super heavy nuclei. The results indicate the acceptability of the approach.

The alpha decay half-lives of even–even and even–odd Platinum (Pt) nuclei have been studied within the Coulomb and proximity potential model (CPPM). The present study is restricted to even–even nuclei with $A=166$–198. The results are compared with other calculations such as the Semi-empirical formula (SemFIS) from Poenaru et al. based on fission theory of alpha decay, the Viola–Seaborg (VS), Royer (R) and Brown formulae. Also, the alpha decay half-lives have been calculated using the Scaling law of Brown (SLB), the Universal Decay Law (UDL) of Qi et al., the Scaling Law of Horoi et al. (SLH), and Akrawy–Dorin formula (ADF) of Akrawy and Poenaru, which are the Royer modified formula for alpha decay half-live by adding asymmetry term.

In this paper, the alpha decay process is investigated through the theoretical approaches for spherical Bismuth (Bi) isotopes in the range 187 $\le$ A $\le$ 214. The results are compared with the experimental data for isotopes of Bi with the modified Coulomb and proximity potential model (MCPPM). We analyze the systematics of alpha decay half-life (HL) of Bi isotopes versus the decay energy and the total $\alpha$-kinetic energy. The results and their systematics are compared with the available experimental data and with those data obtained from empirical models as the Viola-Seaborg (VS) formula, Royer (R) and the two versions of modified Brown (mB) empirical formulas. The computed half-lives (HLs) are compared with the experimental data and also with the existing empirical estimates and are found in good agreement.

Nuclear radial distance is a prerequisite for generating any alpha-decay half-life formula by taking a suitable effective potential. We study the emission process of alpha particles from an isolated quasi-bound state generated by an effective potential to a scattering state. The effective potential is expressed in terms of Frahn form of potential which is exactly solvable and an analytical expression for half-life is obtained in terms of Coulomb function, wave function and the potential. We then derive a closed-form expression for the decay half-life in terms of the parameters of the potential, Q-value of the system, mass and proton numbers of the nuclei valid for alpha-decay as well as proton-decay. From the nature of variations of half-life as a function of radial distance, we trace the radial independence region where decay time is almost constant. Finally, by overviewing our results and picking that particular radial distance, we predict the half-lives of a series of nuclei by using the closed-form expression. We also predict the half-lives of isotopes of nuclei with $Z=119$ and 120.

A set of empirical formulae have been proposed to calculate the $\alpha$-decay half-lives from ground state to ground state transitions of 356 nuclei classified to different set of e–e, e–o, o–e and o–o isotopes. Within these formulae, modification of the previous set of Royer expressions were done by introducing three different physical terms, including the orbital angular momentum and isobaric asymmetry factors. The predicted $\alpha$-decay half-lives compared with those adopted by former proposed models for the depended experimental data, and significant improvements were noticed for all the studied sets of isotopes.

In the present work, we intended to study the $\alpha$-decay half-lives of the even–even nuclei from ${}^{178}$Po to ${}^{226}$Ra in ground state. We investigated a semi-empirical, one-parameter model based on tunneling through a potential barrier with the centrifugal and overlapping effects. Half-lives of $\alpha$-decay of even–even nuclei calculated by using different versions of proximity potentials (gpp77, MCW76 and MB77) are compared to experimental data. Also, the computed half-lives are compared with the Royer formula, Akrawy and Poenaru (AKRE) formula, modify Ren (MRen B) formula and Denisov–Khudenko (DEKH) formula and with the experimental data. The results are in good agreement with the experimental data.