Predictions of direct neutron capture are of vital importance for simulations of nucleosynthesis in supernovae, merging neutron stars, and other astrophysical environments. We calculated direct capture cross sections using nuclear structure information obtained from a covariant density functional theory as input for the fresco coupled reaction channels code. We investigated the impact of pairing, spectroscopic factors, and optical potentials on our results to determine a robust method to calculate cross sections of direct neutron capture on exotic nuclei. Our predictions agree reasonably well with experimental cross section data for the closed shell nuclei ${}^{16}\mathrm{O}$ and ${}^{48}\mathrm{Ca},$ and for the exotic nucleus ${}^{36}\mathrm{S}$. We then used this approach to calculate the direct neutron capture cross section on the doubly magic unstable nucleus ${}^{132}\mathrm{Sn}$ which is of interest for the astrophysical r-process.

Reported oscillations in the rate of decay of certain ions by $K$-electron capture have raised questions about whether and how such oscillations can arise in quantum-mechanical theory and whether they can measure the neutrino mass difference. Here I show that simple principles of quantum mechanics answer some questions and clarify what must be performed theoretically or experimentally to answer some others. The principal result is that quantum mechanics does allow mass-difference-dependent oscillations in principle, but it imposes conditions not obeyed by the approximate dynamical models that have been put forth up to now. In particular, indirect coupling between two neutrino mass channels must be taken into account. What needs to be done experimentally and theoretically is discussed.

We have measured the fission probabilities of ${}^{242}\mathrm{Am},{}^{243}\mathrm{Cm}$, and ${}^{244}\mathrm{Cm}$ induced by the transfer reactions ${}^{243}\mathrm{Am}({}^3\mathrm{He},{}^4\mathrm{He}),{}^{243}\mathrm{Am}({}^3\mathrm{He},t)$, and ${}^{243}\mathrm{Am}({}^3\mathrm{He},d)$, respectively. The details of the experimental procedure and a rigorous uncertainty analysis, including a correlation matrix, are presented. For ${}^{243}\mathrm{Cm}$ our data show clear structures well below the fission threshold. To our knowledge, it is the first time that these structures have been observed for this nucleus. We have compared the measured fission probabilities to calculations based on the statistical model to obtain information on the fission barriers of the produced fissioning nuclei.

Background: Multinucleon transfer reactions have recently attracted attention as a possible path to the synthesis of new neutron-rich heavy nuclei.

Purpose: We study transfer reactions involving massive nuclei with the intention of understanding if the semi-classical model GRAZING coupled to an evaporation and fission competition model can satisfactorily reproduce experimental data on transfer reactions in which fission plays a role.

Methods: We have taken the computer code grazing and have added fission competition to it (grazing-f) using our current understanding of ${\Gamma }_n/{\Gamma }_f$, fission barriers, and level densities.

Results: The code grazing-f seems to satisfactorily reproduce experimental data for $+1p,+2p$, and $+3p$ transfers but has limitations in reproducing measurements of larger above-target and below-target transfers. Nonetheless, we use grazing-f to estimate production rates of neutron-rich $N=126$ nuclei, actinides, and transactinides.

Conclusions: The grazing code, with appropriate modifications to account for fission decay as well as neutron emission by excited primary fragments, does not predict large cross sections for multinucleon transfer reactions leading to neutron-rich transactinide nuclei but predicts opportunities to produce new neutron-rich actinide isotopes.

The phase diagram of finite-isospin, zero-temperature QCD with the pions coupled to photons in a uniform external magnetic field is explored in the low-field, small-isospin-density regime for which chiral perturbation theory is a valid description. For realistic pion masses, the system behaves as a type-II superconductor: a uniform superconducting state is formed at sufficiently low magnetic fields, a vortex state for intermediate magnetic fields, and finally a normal state for large magnetic fields. In each of these phases (including the vortex phase), ${\pi }^0$ remains uncondensed just as in the zero-external-field problem. The critical magnetic field where the phase transition from the uniform superconducting state to a vortex state occurs was found numerically.

Background: Description of the collision process, which includes breakup, is one of the most challenging problems of the quantum mechanics. Recently I have developed a formalism based on the complex-scaling method, which describes accurately nuclear collisions in three- and four-body systems.

Purpose: To provide accurate calculations for $n-{}^3\mathrm{H}$ scattering above the three- and four-nucleon breakup thresholds.

Method: A four-nucleon system is described in configuration space employing Faddeev-Yakubovsky equations. The complex-scaling method is applied to overcome the difficulties related with the complicated boundary conditions.

Results: Elastic observables as well as total breakup cross sections are calculated for neutron scattering on tritium at 14.1, 18, and 22.1 MeV using realistic $\mathit{NN}$ interactions. Excellent agreement is found with the pioneering calculations of this process reported by A. Deltuva et al. [Phys. Rev. C 86, 011001 (2012)]. Strong correlation of the calculated cross sections is established with model-predicted trinucleon binding energy. The forementioned observables reveal little sensitivity to the short-range details of $\mathit{NN}$ interaction.

Conclusion: Reliable and accurate methods are now available to study four-nucleon scattering including the breakup.

The dipolar degrees of freedom on the ${}^{48}\mathrm{Ca}+{}^{27}\mathrm{Al}$ system at 40 MeV/nucleon have been investigated for the first time with the $4\pi$ multidetector CHIMERA. The global variable $\langle Dz\rangle$ was measured for well-reconstructed events in binary dissipative processes. Both the close link with isospin equilibration processes and its insensitivity to later statistical hot source decays have been discussed. This latter feature provides the opportunity to investigate globally and exclusively the dynamics of the equilibration processes. At this first level of investigation the experimental evidence, supported by the study of the reference system ${}^{27}\mathrm{Al}+{}^{40}\mathrm{Ca}$ and the auxiliary one ${}^{27}\mathrm{Ca}+{}^{48}\mathrm{Ca}$, substantially agree with the CoMD-III calculations by describing the isovectorial forces through stiffness parameter values $\gamma \approx 0.8–1.2.$

The thermodynamics of hot and dense matter created in heavy-ion collision experiments are usually studied as a system of infinite volume. Here we report on the possible effects of considering a finite system size for such matter in the framework of a hadron resonance gas model. The bulk thermodynamic variables as well as the fluctuations of conserved charges are considered. We find that the finite size effects are insignificant once the observables are scaled with the respective volumes. The only substantial effect is found in the fluctuations of electric charge which may therefore be used to extract information about the volume of fireball created in heavy-ion collision experiments.

Collinear laser fluorescence spectroscopy has been performed on the ground and isomeric states of ${}^{204,206}\mathrm{Fr}$ in order to determine their spins, nuclear moments, and changes in mean-squared charge radii. A new experimental technique has been developed as part of this work which much enhances the data collection rate while maintaining the high resolution. This has permitted the extension of this study to the two isomeric states in each nucleus. The investigation of nuclear $g$ factors and mean-squared charge radii indicates that the neutron-deficient Fr isotopes lie in a transitional region from spherical towards more collective structures.

The integral measurement of the neutron inelastic cross section leading to the 26-minute half-life ${}^{235m}\mathrm{U}$ isomer in a fission-like neutron spectrum is presented. The experiment has been performed at a pulsed reactor, where the internal conversion decay of the isomer was measured using a dedicated electron detector after activation. The sample preparation, efficiency measurement, irradiation, radiochemistry purification, and isomer decay measurement will be presented. We determined the integral cross section for the ${}^{235}\mathrm{U}(n,n^{\prime }){}^{235m}\mathrm{U}$ reaction to be $1.00\pm 0.13\mathrm{b}$. This result supports an evaluation performed with talys-1.4 code with respect to the isomer excitation as well as the total neutron inelastic scattering cross section.

We study the dynamics of multidimensional quantum tunneling by introducing a complex absorbing potential into a two-dimensional model for spontaneous fission. We first diagonalize the Hamiltonian with the complex potential to determine a resonance state as well as its lifetime. We then solve the time-dependent Schrödinger equation with such basis in order to investigate the tunneling path. We compare this method with the semiclassical method for multidimensional tunneling with imaginary time. A good agreement is found both for the lifetime and for the tunneling path.

High-spin states of ${}^{115}\mathrm{In}$ have been studied using the ${}^{114}\mathrm{Cd}$ (${}^7\mathrm{Li},\alpha 2\mathrm{n}$) reaction at a beam energy of 48 MeV. A total of 13 new transitions have been observed and added to the level scheme of ${}^{115}\mathrm{In}$. Most of the states in ${}^{115}\mathrm{In}$ can be interpreted in terms of the weak coupling of a $g_{9/2}$ proton hole to the core states of ${}^{116}\mathrm{Sn}$ or a $g_{7/2}$ proton to the core states of ${}^{114}\mathrm{Cd}$. A $\Delta I=1$ band with the $\pi {\left(g_{9/2}\right)}^{-1}\otimes \nu {\left(h_{11/2}\right)}^2$ configuration was suggested as an oblate band built on the “stapler” mechanism with the aid of the tilted axis cranking model based on covariant density functional theory.

$\beta$-decay properties of even- and odd-$A$ neutron-rich Ge, Se, Kr, Sr, Ru, and Pd isotopes involved in the astrophysical rapid neutron capture process are studied within a deformed proton-neutron quasiparticle random-phase approximation. The underlying mean field is described self-consistently from deformed Skyrme-Hartree-Fock calculations with pairing correlations. Residual interactions in the particle-hole and particle-particle channels are also included in the formalism. The isotopic evolution of the various nuclear equilibrium shapes and the corresponding charge radii are investigated in all the isotopic chains. The energy distributions of the Gamow-Teller strength as well as the $\beta$-decay half-lives are discussed and compared with the available experimental information. It is shown that nuclear deformation plays a significant role in the description of the decay properties in this mass region. Reliable predictions of the strength distributions are essential to evaluate decay rates in astrophysical scenarios.

Apart from the higher limits of isospin and temperature, the properties of atomic nuclei are intriguing and less explored at the limits of lowest but finite temperatures. At very low temperatures there is a strong interplay between the shell (quantal fluctuations), statistical (thermal fluctuations), and residual pairing effects as evidenced from the studies on giant dipole resonance (GDR). In our recent work [Phys. Rev. C 90, 044308 (2014)], we have outlined some of our results from a theoretical approach for such warm nuclei where all these effects are incorporated along within the thermal shape fluctuation model (TSFM) extended to include the fluctuations in the pairing field. In this article, we present the complete formalism based on the microscopic-macroscopic approach for determining the deformation energies and a macroscopic approach which links the deformation to GDR observables. We discuss our results for the nuclei ${}^{97}\mathrm{Tc},{}^{120}\mathrm{Sn},{}^{179}\mathrm{Au}$, and ${}^{208}\mathrm{Pb}$, and corroborate with the experimental data available. The TSFM could explain the data successfully at low temperature only with a proper treatment of pairing and its fluctuations. More measurements with better precision could yield rich information about several phase transitions that can happen in warm nuclei.

The ${}^{29}\mathrm{Si}$ nucleus has been studied using heavy-ion-induced fusion-evaporation reactions and, for the first time, using a large array of high-resolution $\gamma$-ray detectors. High-spin states of the nucleus are populated using ${}^{18}\mathrm{O}$(${}^{16}\mathrm{O},\alpha n$) and ${}^{18}\mathrm{O}$(${}^{13}\mathrm{C},2n$) reactions at $E_{\mathrm{lab}}=30$–34 MeV. Previously reported levels are confirmed and a new level is identified in the present study. Spin-parity assignments are carried out based on the anisotropy and polarization measurements of the observed $\gamma$ transitions. Level lifetimes are measured using the Doppler shift attenuation method, with modified analysis techniques for the thick molecular target (${\mathrm{Ta}}_2{\mathrm{O}}_5$) used in the present setup. The lifetime of the lowest negative-parity state at $E_x=3624$ keV is substantially modified from the previously reported value. Large-basis shell model calculations are carried out for the nucleus using updated interactions and the results corroborate the experimental findings. The calculations are also carried out for the neighboring ${}^{28,30}\mathrm{Si}$ isotopes. In the case of the ${}^{28}\mathrm{Si}$ nucleus, the calculations adequately reproduce most of the deformed structures, as represented by the quadrupole moments extracted therefrom. In the ${}^{30}\mathrm{Si}$ nucleus, the negative-parity states are reproduced for the first time without any ad hoc lowering of the single-particle energies. It can be generally stated that the shell model calculations adequately describe the experimental observations in these nuclei.

To explore the roles of the dynamical model and statistical model in the description of multifragmentation in heavy-ion collisions at intermediate energies, the fragments charge distributions of ${}^{197}\mathrm{Au}+{}^{197}\mathrm{Au}$ at 35 MeV/u are analyzed by using the hybrid model of improved quantum molecular dynamics (ImQMD) model plus the statistical model GEMINI. We find that, the ImQMD model can well describe the charge distributions of fragments produced in central and semicentral collisions. But for the peripheral collisions of Au+Au at 35 MeV/u, the statistical model is required at the end of the ImQMD simulations for the better description of the charge distribution of fragments. By using the hybrid model of ImQMD+GEMINI, the fragment charge distribution of Au+Au at 35 MeV/u can be reproduced reasonably well. The time evolution of the excitation energies of primary fragments is simultaneously investigated.

First measurement of the beam asymmetry $\Sigma$ for Compton scattering off the proton in the energy range $E_{\gamma }=0.85–1.25\mathrm{GeV}$ is presented. The data reveal two narrow structures at $E_{\gamma }=1.036$ and $E_{\gamma }=1.119 \mathrm{GeV}$. They may signal narrow resonances with masses near 1.68 and $1.72\mathrm{GeV}$, or they may be generated by the sub-threshold $K\Lambda$ and $\omega p$ production. Their decisive identification requires additional theoretical and experimental efforts.

The elastic resonance scattering protons decayed from ${}^{11}\mathrm{B}$ to the ground state of ${}^{10}\mathrm{Be}$ were measured by using the thick-target technique in inverse kinematics at the Heavy Ion Research Facility in Lanzhou (HIRFL). The obtained excitation functions were well described by a multichannel $R$-matrix procedure under the kinematics process assumption of resonant elastic scattering. The excitation energy of the resonant states ranges from 13.0 to 17.0 MeV, and their resonant parameters such as the resonant energy $E_x$, the spin-parity $J^{\pi }$, and the proton-decay partial width ${\Gamma }_p$ were determined from $R$-matrix fits to the data. Two of these states around $E_x=14.55$ MeV [$J^{\pi }=(3/2^{+},5/2^{+}),{\Gamma }_p=475\pm 80$ keV] and $E_x=14.74$ MeV [$J^{\pi }=3/2^{-},{\Gamma }_p=830\pm 145$ keV], and a probably populated state at $E_x=16.18$ MeV [$J^{\pi }=(1/2^{-},3/2^{-}),{\Gamma }_p<60$ keV], are respectively assigned to the well-known states in ${}^{11}\mathrm{B}$ at 14.34, 15.29, and 16.43 MeV. The isospin of these three states were previously determined to be $T=3/2$, but discrepancies exist in widths and energies due to the current counting statistics and energy resolution. We have compared these states with previous measurements, and the observation of the possibly populated resonance is discussed.

The cold ternary fission of ${}^{238}\mathrm{Pu}$, ${}^{240}\mathrm{Pu}$, ${}^{242}\mathrm{Pu}$, and ${}^{244}\mathrm{Pu}$ isotopes, with ${}^4\mathrm{He}$ as light charged particle, in equatorial and collinear configuration has been studied within the unified ternary fission model. The fragment combination ${}^{100}\mathrm{Zr}+{}^4\mathrm{He}+{}^{134}\mathrm{Te}$ possessing the near doubly magic nuclei ${}^{134}\mathrm{Te}(N=82,Z=52)$ gives the highest yield in the α-accompanied ternary fission of ${}^{238}\mathrm{Pu}$. For the α-accompanied ternary fission of ${}^{240}\mathrm{Pu}$, ${}^{242}\mathrm{Pu}$, and ${}^{244}\mathrm{Pu}$ isotopes, the highest yield was found for the fragment combination with doubly magic nuclei ${}^{132}\mathrm{Sn}(N=82,Z=50)$ as the heavier fragment. The deformation and orientation of fragments have also been taken into account for the α-accompanied ternary fission of ${}^{238–244}\mathrm{Pu}$ isotopes, and it has been found that, in addition to the closed-shell effect, ground-state deformation also plays an important role in determining the isotopic yield in the ternary fission process. The emission probability and kinetic energy of long-range α particles have been calculated and are found to be in good agreement with the experimental data.