Narrow Results

The cluster decay process is studied in the WKB approximation based on the unified fission model. The cluster is considered to be emitted by tunneling through a potential barrier taken as the sum of the Coulomb potential, the centrifugal potential and the modified Woods–Saxon (MWS) nuclear potential. The results of our calculations are compared to those obtained by other theoretical models as well as experimental data. It is shown that the unified fission model with the MWS nuclear potential can be successfully used to evaluate the cluster decay half-lives of heavy nuclei.

A precise measurement of elemental abundances of galactic cosmic rays from charges Z = 20 to 34 was made by TIGER balloon experiment. Using the various path lengths in the atmosphere between 4 and 16 g/cm² from the TIGER flight data, we derived the attenuation length of iron nuclei with the energy above 2.5 GeV/n in the atmosphere. As the result, we obtained the attenuation length of 15.5 ± 0.6 g/cm² which is consistent with previous results of balloon measurements.

Recent direct measurements of the energy spectra of the charged cosmic ray have revealed unexpected spectral features, most notably the onset of a progressive hardening at few hundreds of GeV/n not only of proton and He spectra but also observable for heavier nuclei. Thus, the study of the spectra behavior of heavy elements may shed light on understanding propagation and acceleration phenomena in our Galaxy. In particular, Fe and Ni provide favorable conditions for observations thanks to the low background contamination from spallation of higher mass elements they are affected by. The CALorimetric Electron Telescope, CALET, has been measuring high-energy cosmic rays on the International Space Station since October 2015. The instrument consists of two layers of segmented plastic scintillators, a 3 radiation length thick tungsten-scintillating fiber imaging calorimeter and a 27 radiation length thick PWO calorimeter. It identifies the charge of individual elements up to Ni and beyond and it measures the energy of cosmic-ray nuclei providing a direct measurement of their spectra. In this contribution, the iron and nickel spectra, resulted after 5 years of data acquisition, are presented in the energy range between 10 and 2000 GeV/n and between 8.8 and 240 GeV/n, respectively. The analysis procedure and the assessment of systematic errors are detailed, in addition to the ratio between the two fluxes. Both spectra show similar shape and energy dependence.

The deformation structure of the even–even ytterbium, hafnium and tungsten nuclei is investigated in framework of the collective model, the single-particle Schrödinger fluid model and the cranked Nilsson model. Accordingly, we have calculated the rotational and vibrational energies, the nuclear moments of inertia, the total ground-state energy, the quadrupole moment, the liquid drop (LD) energy, the Strutinsky inertia, the LD inertia, the volume conservation factor , the smoothed energy, the Bardeen, Cooper and Schrieffer (BCS) energy and the G-value of the ytterbium: ¹⁷⁰Yb, ¹⁷²Yb and ¹⁷⁴Yb, hafnium: ¹⁷⁶Hf, ¹⁷⁸Hf and ¹⁸⁰Hf and tungsten: ¹⁸²W, ¹⁸⁴W and ¹⁸⁶W nuclei as functions of the deformation parameters β, γ, which are assumed to vary in the ranges (-0.50 ≤ β ≤ 0.50) and (0° ≤ γ ≤ 60°). Also, two polynomials in β are obtained to produce results in good agreement with the corresponding results for the total ground-state energy and the quadrupole moment of the mentioned nine nuclei.

In previous studies, we provided a novel systematization of $\alpha$-decaying even–even and even–odd nuclei starting with the classically adopted mechanism [T. Yarman et al., Eur. Phys. J. A52 (2016) 140; Eur. Phys. J. A53 (2017) 4]. Knowing beforehand the measured decay half-life, we had taken as a parameter the probability of the $\alpha$-particle as being first born in a unit period of time, within the parent nucleus before it is emitted out. We thence developed a scaffold based on shell properties of families composed of “alike nuclei”. Along the same line, we now present a systematization of odd–even (OE) as well as odd–odd (OO) nuclei. We apply our approach further to the investigation of the effect of pairing (e.g., the effect when the number of nucleons is increased by one neutron), and that of unpairing (e.g., the effect when the number of nucleons is decreased by one neutron); thus it becomes an even number for the case of odd–even nuclei $($Case OE$)$, and an odd number in the case of odd–odd nuclei $($Case OO$)$. For the first case $($OE$)$, we pick the exemplar set ${}^{161}$Re, ${}^{217}$Fr, ${}^{243}$Bk, ${}^{263}$Db; where we delineate by, respectively, Re, Fr, Bk, and Db all of the odd–even or odd–odd isotopes that neighbor the four mentioned odd–even isotopes on the proposed scaffold. We proceed in the same way for the second case $($OO$)$. Thus, we choose the exemplar set of odd–odd nuclei ${}^{172}$Ir, ${}^{218}$Ac, ${}^{244}$Es. We then gather all of the Ir, Ac, and Es odd–odd and odd–even isotopes that neighbor the three mentioned odd–odd isotopes on the proposed scaffold. We show that, in the former case, pairing, as expected, generally increases stability of the given nucleus; and in the latter case, unpairing works in just the opposite direction — i.e., it generally increases instability. We disclose “stability peaks” versus $Z$ for both sets of nuclei, we tackle here. Furthermore, we present a study to highlight an outlook of “odd-A nuclei” at hand. Contrary to the general expectation, we unveil no systematic on that.

In this work, the spectra of some even–even isotopes are studied by selecting core-cluster decomposition of the parent nucleus. The considered nuclei lie in the rare-earth and the transition metal regions. The Schrödinger equation can be solved using Bohr–Sommerfeld relation and the modified Woods–Saxon beside Coulomb potentials to reproduce the spectra of these isotopes with mass number $(154\le A\le 168)$. The theoretical calculations of the excitation energies of the ground state rotational band are compared to the experimental data. The cluster model calculations show a good agreement with the experimental data for the transitional and rotational nuclei more than the vibrational nuclei. Some negative parity bands of the chosen nuclei are studied. The core-cluster charge products are correlated with the transition probability $B(E2:2^{+}\to 0^{+})$.

${}^{14}$C is a beta decay isotope, its beta decay is very slow reflecting the stability of this nucleus and emitted from medium and heavy mass nuclei. The ${}^{14}$C result is in excellent agreement with the favored ground-state-to-ground-state transition according to the cluster model of Blendowske et al. We study nuclear structure properties of spin-1/2 heavy nuclei in the relativistic core-cluster model, that its cluster is ${}^{14}$C. According to this model for spin-1/2 heavy nuclei and for obtaining its wave function, we solve the Dirac equation with the new phenomenological potential by parametric Nikiforov–Uvarov method and then calculate the binding energy and charge radius.

In this study, the half-lives of $\alpha$-decay from some heavy nuclei in the range $82\le Z\le 90$ have been studied using the WKB semi-classical approximation. The nuclear interaction potential between the $\alpha$-particle and the daughter nuclei is obtained within the double folding model. The $\mathrm{\text{NN}}$ interactions employed are those derived from relativistic mean field (RMF) theory, called as R3Y $\mathrm{\text{NN}}$ interactions. Six different R3Y $\mathrm{\text{NN}}$ interactions are considered in the study to determine the most appropriate R3Y parametrization for heavy nuclei. Some of the R3Y interactions (such as R3Y-HS, R3Y-L1, R3Y-Z, R3Y-W) contain only linear $\sigma$, $\omega$, and $\rho$ mesons, while the others (such as R3Y-NL2, R3Y-NLSH) contain nonlinear terms, in addition to the linear terms. All the R3Y $\mathrm{\text{NN}}$ interactions used are found to be efficient in describing the $\alpha$-decay half-lives data. However, R3Y $\mathrm{\text{NN}}$ interactions containing nonlinear terms are found to perform better than those containing only linear terms of the mesons.

The nucleus can be considered a relativistic system, In particular, we focus on heavy nuclei with zero spin and utilize the relativistic core-cluster model to investigate their structure properties. A zero-spin nucleus is assumed to consist of a core and a cluster, core and cluster spins are zero. We will solve the Klein–Gordon equation, which is a relativistic equation optimized for studying zero-spin systems, with the new phenomenological potential. Then, we will calculate the binding energy and charge radius of the zero-spin heavy nuclei by employing the wave function obtained from the Klein–Gordon equation.

In this paper, we model the fission process by assuming that at certain elongation, after crossing the fission barrier, a fissile nucleus can be treated as a superposition of dinuclear systems (DNS). The distribution of primary fission fragments is described as a result of competition between evolution of initially formed DNS and its decay in relative distance. The level densities required for the calculations were microscopically derived accounting for deformation and excitation energy effects. The calculations performed for even ${}^{244-260}$Fm isotopes give overall good description of mass and neutron multiplicity distributions. To describe sudden onset of symmetric fission in ${}^{258}$Fm, the fissile nucleus is treated as superposition of DNS at smaller elongations than for lighter Fm isotopes, which is in line with significant reduction of half-life for ${}^{258}$Fm. Our results indicate the presence of bimodality due to coexistence of spherical and deformed mass symmetric fission modes.

I undertake an anatomy of the nuclear electric-dipole spectrum and discuss selected observations. First, using data and calculations on ²⁰⁸Pb as a representative case, I identify five conspicuous structures in the spectra of heavy nuclei: (1) the giant dipole resonance (GDR), (2) the dipole compression mode, (3) the isoscalar low-energy dipole mode (ISLED), (4) the IS mode in the region of the GDR, and (5) a concentration of “pygmy” dipole strength (PDS) between the latter two. Next, compiling the data from Texas A&M I show that the energy of (4) follows roughly a A^−1/6 dependence on the mass number. Finally, I summarize recent theoretical studies on the PDS in exotic nuclei, which suggest a strong influence of shell effects and loose binding.

The isotopic dependence of two-quasiparticle isomeric states in Fm and No is treated. An α-decay chain through the isomeric states of super-heavy nuclei is demonstrated. The excitation energies and the structure of the low lying states with K^π = 0^‒ 1^‒ 2^‒ are calculated with the quasiparticle phonon model.