We account for the extremely long ($\sim$10${}^{18}$ yr) as well as short ($\sim$10${}^{-4}$ s) lifetimes of $\alpha$ decay in the cases of naturally occurring heavy $\alpha$ emitters with proton number $Z=58$–82 and successfully predict the results via an analytical expression for the decay half-life, developed by using an exactly solvable global potential in the theory of potential scattering.

Previously unknown states in ${}^{18}$Na and ${}^{19}$Mg have been studied by measuring the trajectories of their decay products with microstrip detectors. Analyzing angular correlations of the fragments provided information on decay energies and widths of the parent states. The ground state of ${}^{18}$Na has been detected and its one-proton decay energy of 1.23(15) MeV determined. Four previously unknown states in ${}^{19}$Mg at 2.1, 2.9, 3.6, and 5.2 MeV have been observed. The competition between simultaneous and sequential two-proton emission of states in ${}^{19}$Mg is discussed, and the conclusion of a direct mechanism of $2p$ radioactivity of the ${}^{19}$Mg ground state is confirmed.

Background: The evolution of and interplay between single-particle and collective excitations in the 40 $⩽N⩽$ 50 range for ${}_{38}$Sr and ${}_{40}$Zr isotopes have been studied.

Purpose: Measurement of the $g$ factor of the 2${}_1^{+}$ and 4${}_1^{+}$ states in radioactive ${}^{88}$Zr while simultaneously remeasuring the $g\left(2_1^{+}\right)$ factors in the Sr isotopes and extention of the measurements to higher energy states in the Sr isotopes. Lifetimes of states in these nuclei are determined.

Methods: The transient field technique in inverse kinematics and line-shape analysis using the Doppler-shift attenuation method are applied. The ${}^{88}$Zr nuclei were produced by the transfer of an $\alpha$ particle from the ${}^{12}$C nuclei of the target to ${}^{84}$Sr nuclei in the beam. The excited states in the stable ${}^{84}$Sr isotopes were simultaneously populated via Coulomb excitation by ${}^{12}$C in the same target. Coulomb excitation measurements on ${}^{86,88}$Sr were carried out with the same apparatus.

Results: The resulting $g$ factors and $B\left(E2\right)$ values of these nuclei reveal similarities between the two chains of Zr and Sr isotopes. Large-scale shell-model calculations were performed within the $p_{3/2},f_{5/2},p_{1/2},g_{9/2}$ orbital space for both protons and neutrons and yielded results in agreement with the experimental data.

Conclusions: In this paper the magnetic moments and lifetimes of several low-lying states in ${}^{88}$Zr and ${}^{84.86,88}$Sr have been measured and compared to large-scale shell-model calculations.

In a quantum Fermi system the energy per particle calculated at the second order beyond the mean-field approximation diverges if a zero-range interaction is employed. We have previously analyzed this problem in symmetric nuclear matter by using a simplified nuclear Skyrme interaction, and proposed a strategy to treat such a divergence. In the present work, we extend the same strategy to the case of the full nuclear Skyrme interaction. Moreover we show that, in spite of the strong divergence ($\sim$${\Lambda }^5$, where $\Lambda$ is the momentum cutoff) related to the velocity-dependent terms of the interaction, the adopted cutoff regularization can be always simultaneously performed for both symmetric and nuclear matter with different neutron-to-proton ratios. This paves the way for applications to finite nuclei.

We systematically investigate the influence of nuclear deformations on the $\alpha$-decay half-lives of the deformed medium, heavy, and superheavy nuclei for $106⩽A⩽273$ and $52⩽Z⩽110$ from the ground state to ground state $\alpha$ transitions within the framework of the Wentzel--Kramers--Brillouin (WKB) method by considering the Bohr-Sommerfeld quantization condition. The deformed Wood-Saxon form in a phenomenological way and the deformed Coulomb potential in a special form have been used in order to take into account all deformation effects in the calculations and the preformation of the parent nuclei have also been regarded. Calculations have been conducted for the spherical nuclei in order to present clearly the effects of the deformations on the half-lives. We point out that all considerations have improved the results and very good agreement has been obtained with experimental data.

Evaporation-residue-gated high-energy gamma-ray spectra were measured in the ${}^{19}$F+${}^{27}$Al reaction at two beam energies of $\sim$75 and 125 MeV. The compound nuclear angular momenta populated at the higher energy should extend beyond the critical value for the Jacobi shape transition, while those at the lower energy should be mostly restricted below the critical value. A sharp low-energy (at $\sim$10 MeV) component has been observed in the gamma-ray strength function superimposed on a broad distribution. At the higher beam energy, the component becomes more prominent at higher angular momentum, whereas an opposite behavior is witnessed at the lower beam energy. The implication of these observations in connection with the occurrence of the Jacobi shape transition is discussed.

Background: There is a long-term interest in running the fission reaction backward, i.e., studying the “inverse fission” of uranium. The recent availability of beams of $n$-rich fission fragments has stimulated interest in this endeavor.

Purpose: To search for inverse fission in the reactions ${}^{124,132}$Sn + ${}^{100}$Mo.

Method: In the ${}^{124}$Sn + ${}^{100}$Mo reaction, evaporation residues were searched for using in-beam detection of evaporation residues, in-beam $\alpha$ spectroscopy, and post-irradiation $\alpha$ spectroscopy, while in the ${}^{132}$Sn + ${}^{100}$Mo reaction, the evaporation residue ${}^{230}$U was searched for using post-irradiation $\alpha$ spectroscopy.

Results: No evidence for the occurrence of the inverse fission reactions was found. The upper-limit cross section for the latter reaction is $\sim$550 $\mu$b, while the experimental upper-limit cross section for the former reaction is about 21${}_{-21}^{+38}$ nb.

Conclusions: The intensity of suitable radioactive beams is not high enough at present to detect inverse fission. For the ${}^{124}$Sn + ${}^{100}$Mo reaction, the observed upper limits are below the estimates of current models for these reactions, probably due to fusion hindrance.

The azimuthal anisotropies of the collective transverse flow of charged hadrons are investigated in a wide range of heavy-ion collision energies within the microscopic parton-hadron-string dynamics (PHSD) transport approach, which incorporates explicit partonic degrees of freedom in terms of strongly interacting quasiparticles (quarks and gluons) in line with an equation of state from lattice QCD as well as the dynamical hadronization and hadronic collision dynamics in the final reaction phase. The experimentally observed increase of the elliptic flow $v_2$ of charged hadrons with collision energy is successfully described in terms of the PHSD approach. The PHSD scaling properties of various collective observables are confronted with experimental data as well as with hydrodynamic predictions. The analysis of higher-order harmonics $v_3$ and $v_4$ in the azimuthal angular distribution shows a similar tendency of growing deviations between partonic and purely hadronic models with increasing collision energy. This demonstrates that the excitation functions of azimuthal anisotropies reflect the increasing role of quark-gluon degrees of freedom in the early phase of relativistic heavy-ion collisions. Furthermore, the specific variation of the ratio $v_4/{\left(v_2\right)}^2$ with respect to bombarding energy, centrality, and transverse momentum is found to provide valuable information on the underlying dynamics.

The relatively short-lived radionuclide ${}^{44}$Ti is of considerable importance for the interpretation of nucleosynthesis in core-collapse supernova environments. Production is predominantly through the ${}^{40}$Ca($\alpha$,$\gamma$)${}^{44}$Ti reaction, which has been studied in this work over the energy range $E_{\mathrm{cm}}=2.73$–4.18 MeV, via direct $\gamma$ counting and the 4$\pi$-summing technique, utilizing a previously characterized 12 inch $\times$ 12 inch single NaI crystal. The inferred reaction rate is compared here to both current experimental measurements and theoretical model calculations.

The variation after projection approach is applied for the first time to the Richardson pairing Hamiltonian to describe the thermodynamics of small superconductors with a fixed number of particles. The minimization of the free energy is made by a direct diagonalization of the entropy. The variation after projection applied at finite temperature provides a perfect reproduction of the exact canonical properties of odd or even systems from very low to high temperatures.

Recent accurate data obtained for the isomeric cross section of the ${}^{197}$Au$(n,2n)$ reaction provide a valuable opportunity to consider the question of the effective moment of inertia of the nucleus within a local consistent model analysis of all available reaction data for the ${}^{197}$Au target nucleus. Thus, a definite proof of a moment of inertia equal to that of the rigid-body has been obtained for the ${}^{196}$Au nucleus, while indications infer about half the rigid-body for ${}^{194}$Ir.

A study of ${}^{26}$Si states by neutron removal from a fast radioactive beam of ${}^{27}$Si has been performed. A beam of ${}^{27}$Si of energy 84.3 MeV/nucleon impinged on a polypropylene foil (C${}_3$H${}_6$) of 180 mg/cm${}^2$ thickness. Deexcitation $\gamma$ rays were detected with a highly segmented germanium detector array, in coincidence with the ${}^{26}$Si recoils, and the corresponding ${}^{26}$Si level energies were determined. In comparing our results to two previous $\gamma$-ray spectroscopic studies of ${}^{26}$Si level structures, we find good agreement with a recent measurement of the ${}^{12}$C(${}^{16}$O,$2n\gamma$)${}^{26}$Si reaction. Our results support the use of excitation energies from that study in helping determine the important resonance energies for the thermonuclear ${}^{25}$Al($p,\gamma$)${}^{26}$Si reaction rate. We do not observe a bound state at 4093 keV reported in an earlier study of the ${}^{24}$Mg(${}^3$He,$n\gamma$)${}^{26}$Si reaction.

Recently published measurements of the two-nucleon short range correlation ($NN$-SRC) scaling factors, $a_2(A/d)$, strengthen the previously observed correlation between the magnitude of the EMC effect measured in electron deep inelastic scattering at $0.35⩽x_B⩽0.7$ and the SRC scaling factor measured at $x_B⩾1$. The new results improve precision and include previously unmeasured nuclei. The measurements of $a_2(A/d)$ for ${}^9$Be and ${}^{197}$Au agree with published predictions based on the EMC-SRC correlation. This Brief Report examines the effects of the new data and of different corrections to the data on the slope and quality of the EMC-SRC correlation, the size of the extracted deuteron in-medium correction effect, and the free-neutron structure function. The results show that the linear EMC-SRC correlation is robust and that the slope of the correlation is insensitive to most combinations of corrections examined in this work. This strengthens the interpretation that both $NN$-SRC and the EMC effect are related to high-momentum nucleons in the nucleus.

We present a workable model for the fermion-photon vertex, which is expressed solely in terms of functions that appear in the fermion propagator and independent of the angle between the relative momenta, and does not explicitly depend on the covariant-gauge parameter. It nevertheless produces a critical coupling for dynamical chiral symmetry breaking that is practically independent of the covariant-gauge parameter and an anomalous magnetic moment distribution for the dressed fermion that agrees in important respects with realistic numerical solutions of the inhomogeneous vector Bethe-Salpeter equation.

The structure of ${}^{13}$Be was investigated with antisymmetrized molecular dynamics. The variation after spin and parity projections was performed. An unnatural parity $1/2^{-}$ state was suggested to be lower than the $5/2^{+}$ state indicating that vanishing of the $N=8$ magic number occurs in ${}^{13}$Be. A low-lying $3/2^{+}$ state with a $2\hslash \omega$ configuration was also suggested. Developed cluster structures were found in the intruder states. The lowering mechanism of the intruder states was discussed in terms of molecular orbitals around a $2\alpha$ core.

We analyze the role of the symmetry energy slope parameter $L$ on the $r$-mode instability of neutron stars. Our study is performed using both microscopic and phenomenological approaches of the nuclear equation of state. The microscopic ones include the Brueckner-Hartree-Fock approximation, the well known variational equation of state of Akmal, Pandharipande, and Ravenhall, and a parametrization of recent auxiliary field diffusion Monte Carlo calculations. For the phenomenological approaches, we use several Skyrme forces and relativistic mean-field models. Our results show that the $r$-mode instability region is smaller for those models which give larger values of $L$. The reason is that both bulk ($\xi$) and shear ($\eta$) viscosities increase with $L$ and, therefore, the damping of the mode is more efficient for the models with larger $L$. We show also that the dependence of both viscosities on $L$ can be described at each density by simple power-laws of the type $\xi =A_{\xi }{L}^{B_{\xi }}$ and $\eta =A_{\eta }{L}^{B_{\eta }}$. Using the measured spin frequency and the estimated core temperature of the pulsar in the low-mass x-ray binary 4U 1608-52, we conclude that observational data seem to favor values of $L$ larger than $\sim$50 MeV if this object is assumed to be outside the instability region, its radius is in the range 11.5–12 (11.5–13) km, and its mass $1.4M_{\odot }$ ($2M_{\odot }$). Outside this range it is not possible to draw any conclusion on $L$ from this pulsar.

The similarity renormalization group (SRG), based on the simple one-body free harmonic oscillator Hamiltonian, is applied to various nucleon-nucleon realistic interactions to investigate the unitarity of the SRG transformations. Two-body and three-body contributions to the SRG-evolved Hamiltonian are studied in the framework of spectral distribution theory for reasonable SRG cutoffs and in multiparticle systems, with up through 28 particles considered. The outcome points to the first evidence for the overall importance of three-body SRG-induced interactions and especially, of its two-body effective content in multinucleon systems, without the need for large-scale shell model calculations for many light to heavier nuclei.

Radiative neutron capture cross sections have been measured for the stable isotopes of natural Os with mass numbers 184, 189, 190, and 192 by observing radioactive decays of the activation products following neutron irradiation of naturally occurring Os. From irradiations of Os samples separately with thermal and epithermal neutrons, independent values of the thermal cross sections and resonance integrals have been deduced. By observing the $\gamma$ rays emitted by the activation products ${}^{185}$Os, ${}^{190}$Os${}^m$, ${}^{191}$Os, and ${}^{193}$Os, improved values for the energies and intensities of the $\gamma$ rays and the decay half-lives have been obtained, enabling corresponding improvements in the energy values and $\beta$-decay feedings of levels in the daughter nuclei.

Elastic scattering observables (differential cross section and analyzing power) are calculated for the reaction ${}^6$He($p$,$p$)${}^6$He at projectile energies starting at 71 MeV/nucleon. The optical potential needed to describe the reaction is derived by describing ${}^6$He in terms of a ${}^4$He core and two neutrons. The Watson first-order multiple-scattering ansatz is extended to accommodate the internal dynamics of a composite cluster model for the ${}^6$He nucleus scattering from a nucleon projectile. The calculations are compared with recent experiments at the projectile energy of 71 MeV/nucleon. In addition, differential cross sections and analyzing powers are calculated at selected higher energies.