Narrow Results

The effect of tensor interaction is discussed on the deformation and the shell structure of heavy and superheavy nuclei within the deformed Skyrme Hartree-Fock+BCS model. The importance of the tensor correlations is shown for the single particle spectra of protons in ²⁴⁹Bk. The large shell gaps of superheavy nuclei are found at Z = 114 and Z = 120 for protons and N = 184 for neutrons with the spherical shape irrespective of the tensor correlations. It is also shown that Z = 114 and N = 164 shell gaps are more pronounced by the tensor correlations in the case of SLy5+T interaction.

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 $104\le Z\le 130$.

We have investigated the synthesis of superheavy elements using Cr-induced fusion reactions. We have studied all possible Cr-induced fusion reactions for the synthesis of super heavy nuclei $104\le Z\le 123$. We have achieved the semi-empirical formula for fusion barrier heights ($V_B$), positions ($R_B$), curvature of the inverted parabola ($\hslash \omega$) of Cr-induced fusion reactions for the synthesis of superheavy nuclei with atomic number range $104\le Z\le 123$. The proposed formula produces fusion barriers of Cr-induced fusion reactions for the synthesis of super heavy nuclei with the simple inputs of mass number ($A$) and atomic number ($Z$) of projectile-targets. We have also identified the targets for Cr-induced fusion reactions to synthesis superheavy elements of $104\le Z\le 123$. We have also studied the entrance channel parameters such as mass asymmetry ($\eta$), charge asymmetry (${\eta }_z$), coulomb interaction parameter ($Z$’), Businaro–Gallone mass asymmetry parameter (${\alpha }_{\mathrm{\text{BG}}}$) and Isospin asymmetry parameter [$\delta (N/Z)$]. We hope that our predictions may be the guide for the future experiments in the synthesis of more superheavy elements using ${}^{54}$Cr-induced fusion reactions.

We have performed a systematic study for the nuclear structure of superheavy nuclei with a special emphasis on the nuclei with possible central depletion of proton and neutron density in the mass region $\mathrm{\text{A}}\sim 300$ using the Relativistic Hartree–Bogoliubov (RHB) framework. It has been observed that in the case of neutron density distribution, the occurrence of central depletion is related to the occupancy of 4s orbital and it is found to decrease with increasing occupancy of the 4s orbital. On the other hand, in the case of proton density distribution, the central density depletion is mainly due to the lowering of weakly bound p-orbital states close to the continuum as it is energetically favored to lower the Coulomb repulsion in the case of superheavy nuclei. Also, occupation probability of the lower angular momentum states (p-orbitals) lying near the Fermi level is strongly suppressed due to the weak centrifugal barrier and strong Coulomb repulsion in comparison to large angular momentum states (contributing to surface region mainly), resulting in central density depletion. Among the considered cases in the present work, the maximum depletion is observed for ${}^{292}120$ and for ${}^{294}$Og under spherically symmetric and axially deformed cases, respectively.

Using 377 available experimental data, we have obtained an empirical formula to calculate alpha decay half-lives based on Geiger–Nuttall law for even–even, even–odd, odd–even and odd–odd nuclei. The coefficients of Geiger–Nuttall law have been modified as a function of the atomic number of the parent nucleus and the orbital angular momentum. The obtained root mean square deviations from experimental half-lives for even–even, even–odd, odd–even and odd–odd nuclei are 0.3265, 0.5412, 0.4848 and 0.4353, respectively. For most nuclei, the obtained results from this formula are in good agreement with the experimental data. We compared our results with other formulas such as universal decay law, Royer, AKRA, MYQZR and Luo. Also, using this formula, we presented predictions for superheavy nuclei with $Z=118$–124 using the $Q$-values based on the finite range droplet model and Weizsäcker–Skyrme. It is found that the behavior of the half-life of alpha decay is sensitive to the used $Q$-values.

The evaporation residue cross section of synthesizing superheavy elements requires touching probability, formation probability and survival probability. Survival probability and evaporation residue cross section appear in the last stage of synthesizing superheavy element. There are many uncertain parameters in each stage, here we focused on uncertain parameter in the survival probability that has also affect the evaporation residue cross section. As the parameters change, the calculation results also change. To adjust these parameters to fit with experiment value, we adopt the covariance method to arrange it more mathematically. There are also many possible systems for the same element especially the element that has not been discovered yet.

Recent experiments using actinide + ⁴⁸Ca reactions have led to the discovery of five new elements and more than 50 new isotopes on the “hot fusion” island. These new nuclei, all having a large neutron excess over protons, provide strong evidence for the existence of the proposed island of stability for superheavy nuclei. As atomic number Z increases beyond Z = 115, the reaction cross sections are decreasing, requiring new approaches for continued progress. Ion beams heavier than ⁴⁸Ca will be required to reach elements above Z = 118, and new actinide target technologies and separation capabilities will be needed to accommodate higher beam intensities and optimize the use of heavier ²⁵¹Ca targets in experiments. In this paper, we review the availability of actinide materials, the use of new target/projectile combinations, and related experimental opportunities, including prospects for new element discoveries and for approaching the presumed closed shell at N = 184. Research opportunities include ongoing experiments to produce the heaviest nuclei to date using mixed Cf targets, and measurements of excitation functions for ⁴⁸Ca and ⁵⁰Ti on Pu and Cm targets to estimate cross sections for planned experiments using ⁵⁰Ti beams on ²⁴⁹Bk and ²⁵¹Cf for synthesis of elements 119 and 120. New developments for the production of ²⁴⁹Bk and for increasing the availability of ²⁵¹Cf and possibly ²⁵⁴Es are described.