The ${}^{15}\mathrm{O}$($\alpha ,\gamma$)${}^{19}\mathrm{Ne}$ reaction plays a role in the ignition of type I x-ray bursts on accreting neutron stars. The lifetimes of states in ${}^{19}\mathrm{Ne}$ above the ${}^{15}\mathrm{O}$$+\alpha$ threshold of 3.53 MeV are important inputs to calculations of the astrophysical reaction rate. These levels in ${}^{19}\mathrm{Ne}$ were populated in the ${}^3\mathrm{He}$(${}^{20}\mathrm{Ne}$,$\alpha$)${}^{19}\mathrm{Ne}$ reaction at a ${}^{20}\mathrm{Ne}$ beam energy of 34 MeV. The lifetimes of six states above the threshold were measured with the Doppler-shift attenuation method. The present measurements agree with previous determinations of the lifetimes of these states and in some cases are considerably more precise.

We study neutron matter at and near the unitary limit using a low-momentum ring diagram approach. By slightly tuning the meson-exchange CD-Bonn potential, neutron-neutron potentials with various ${}^1{S}_0$ scattering lengths such as $a_s=-12070$ fm and $+21$ fm are constructed. Such potentials are renormalized with rigorous procedures to give the corresponding $a_s$-equivalent low-momentum potentials $V_{\text{low-}k}$, with which the low-momentum particle-particle hole-hole ring diagrams are summed up to all orders, giving the ground state energy $E_0$ of neutron matter for various scattering lengths. At the limit of $a_s\to \pm \infty$, our calculated ratio of $E_0$ to that of the noninteracting case is found remarkably close to a constant of 0.44 over a wide range of Fermi-momenta. This result reveals an universality that is well consistent with the recent experimental and Monte Carlo computational study on low-density cold Fermi gas at the unitary limit. The overall behavior of this ratio obtained with various scattering lengths is presented and discussed. Ring-diagram results obtained with $V_{\text{low-}k}$ and those with $G$-matrix interactions are compared.

The ${}^{19}\mathrm{F}$($\alpha ,p$)${}^{22}\mathrm{Ne}$ reaction is considered to be one of the main sources of fluorine depletion in AGB and Wolf-Rayet stars. The reaction rate still retains large uncertainties due to the lack of experimental studies available. In this work the yields for both exit channels to the ground state and first excited state of ${}^{22}\mathrm{Ne}$ have been measured and several previously unobserved resonances have been found in the energy range $E_{\mathrm{lab}}=792\text{−}1993$ keV. The level parameters have been determined through a detailed $R$-matrix analysis of the reaction data and a new reaction rate is provided on the basis of the available experimental information.

We have studied the α-condensed states of ${}^{16}\mathrm{O}$ and ${}^{20}\mathrm{Ne}$ based on a microscopic α-cluster model. This was performed by introducing a Monte Carlo technique for the description of the THSR (Tohsaki Horiuchi Schuck Röpke) wave function, which is called the “virtual THSR” wave function. Earlier microscopic calculations pointed out the possibility of the existence of four-α-cluster condensed states. Here, in addition to studying the four-α case, we also studied the case of five-α particles, for which the states are shown to be stable around the threshold energy even after taking into account the coupling effect between normal cluster states with ${}^{16}\mathrm{O}$$+\alpha$ configurations.

Analyzing powers have been measured for the ${}^{40}\mathrm{Ca}$($\overrightarrow{p},p\alpha$)${}^{36}\mathrm{Ar}$ reaction at an incident energy of 100 MeV for coplanar scattering angles corresponding to zero recoil momentum of the residual nucleus. Predictions based on the distorted wave impulse approximation fail to reproduce the data.

Production of nuclei above ${}^{100}\mathrm{Sn}$ in fusion-evaporation reactions between ${}^{58}\mathrm{Ni}$ and ${}^{54}\mathrm{Fe}$ ions was studied at Oak Ridge National Laboratory by means of the recoil mass spectrometer and charged particle detection. The beam energy was varied to optimize the yields for the two-, three- and four-particle evaporation channels. Experimental results verified the predictions of the statistical model code HIVAP. The optimum energy for the ${}^{54}\mathrm{Fe}$(${}^{58}\mathrm{Ni}$,$4n$)${}^{108}\mathrm{Xe}$ reaction channel that allows one to study the ${}^{108}\mathrm{Xe}$-${}^{104}\mathrm{Te}$-${}^{100}\mathrm{Sn}$ α decay chain is deduced as 240 MeV.

Using the alpha ($\alpha$)-cluster structure of ${}^{12}\mathrm{C}$ nucleus, two versions of the ${}^{12}\mathrm{C}+{}^{12}\mathrm{C}$ real double folded optical potentials have been generated based upon effective $\alpha \text{−}\alpha ,\alpha$-nucleon ($N$) and $N\text{−}N$ interactions. The obtained potentials, in conjunction with shallow phenomenological Woods-Saxon imaginary parts, successfully reproduce the elastic scattering differential cross section for 12 sets of data over the broad energy range $70\text{−}360$ MeV. No renormalization of the real folded potentials is required to fit the data. The energy dependence of the extracted real and imaginary volume integrals and total reaction cross section is investigated.

A relativistic and quantum mechanical framework to compute nuclear transparencies for pion photo- and electroproduction reactions is presented. Final-state interactions for the ejected pions and nucleons are implemented in a relativistic eikonal approach. At sufficiently large ejectile energies, a relativistic Glauber model can be adopted. At lower energies, the framework possesses the flexibility to use relativistic optical potentials. The proposed model can account for the color-transparency (CT) phenomenon and short-range correlations (SRC) in the nucleus. Results are presented for kinematics corresponding to completed and planned experiments at Jefferson Lab. The influence of CT and SRC on the nuclear transparency is studied. Both the SRC and CT mechanisms increase the nuclear transparency. The two mechanisms can be clearly separated, though, as they exhibit a completely different dependence on the hard-scale parameter. The nucleon and pion transparencies as computed in the relativistic Glauber approach are compared with optical-potential and semiclassical calculations. The similarities in the trends and magnitudes of the computed nuclear transparencies indicate that they are not subject to strong model dependences.

Isotopes of rutherfordium (${}^{258-261}\mathrm{Rf}$) were produced in irradiations of ${}^{238}\mathrm{U}$ targets with ${}^{26}\mathrm{Mg}$ beams. Excitation functions were measured for the $4n,5n$, and $6n$ exit channels. Production of ${}^{261}\mathrm{Rf}$ in the $3n$ exit channel with a cross section of ${28}_{-26}^{+92}$ pb was observed. $\alpha$-decay of ${}^{258}\mathrm{Rf}$ was observed for the first time with an $\alpha$-particle energy of 9.05 ± 0.03 MeV and an $\alpha /$total-decay branching ratio of 0.31 ± 0.11. In ${}^{259}\mathrm{Rf}$, the electron capture/total-decay branching ratio was measured to be $0.15\pm 0.04$. The measured half-lives for ${}^{258}\mathrm{Rf}$, ${}^{259}\mathrm{Rf}$, and ${}^{260}\mathrm{Rf}$ were $14.7_{-1.0}^{+1.2}$ ms, $2.5_{-0.3}^{+0.4}$ s, and $22.2_{-2.4}^{+3.0}$ ms, respectively, in agreement with literature data. The systematics of the $\alpha$-decay $Q$-values and of the partial spontaneous fission half-lives were evaluated for even-even nuclides in the region of the $N=152,Z=100$ deformed shell. The influence of the $N=152$ shell on the $\alpha$-decay $Q$-values for rutherfordium was observed to be similar to that of the lighter elements ($96⩽Z⩽102$). However, the $N=152$ shell does not stabilize the rutherfordium isotopes against spontaneous fission, as it does in the lighter elements ($96⩽Z⩽102$).

We describe measurements of the parity-violating ($P\text{−}\mathrm{odd}$) triton emission asymmetry coefficient $a_{P\text{−}\mathrm{odd}}$ in the ${}^6\mathrm{Li}$$(n,\alpha )$${}^3\mathrm{H}$ reaction with polarized cold neutrons. Experiments were carried out at the Petersburg Nuclear Physics Institute (Gatchina, Russia) and at the Institut Laue-Langevin (Grenoble, France). We employed an ionisation chamber in a configuration allowing us to suppress the left-right asymmetry well below ${10}^{-8}$. An additional test for a false asymmetry due to eventual target impurities (“zero test”) resulted in $a_{0\text{−}\mathrm{test}}=(0.0\pm 0.5)\times {10}^{-8}$. As final result of this series of experiments we obtained $a_{P\text{−}\mathrm{odd}}=(-8.8\pm 2.1)\times {10}^{-8}$.

High energy γ rays in coincidence with low energy yrast γ rays have been measured from ${}^{113}\mathrm{Sb}$, at excitation energies of 109 and 122 MeV, formed by bombarding ${}^{20}\mathrm{Ne}$ on ${}^{93}\mathrm{Nb}$ at projectile energies of 145 and 160 MeV, respectively, to study the role of angular momentum ($J$) and temperature ($T$) over giant dipole resonance (GDR) width (Γ). The maximum populated angular momenta for fusion were $67\hslash$ and $73\hslash$, respectively, for the above-mentioned beam energies. The high energy photons were detected using a Large Area Modular BaF${}_2$ Detector Array (LAMBDA) along with a 24-element multiplicity filter. After pre-equilibrium corrections, the excitation energy $E^{*}$ was averaged over the decay steps of the compound nucleus (CN). The average values of temperature, angular momentum, CN mass, etc., have been calculated using the statistical model code CASCADE. Using those average values, results show the systematic increase of GDR width with $T$, which is consistent with Kusnezov parametrization and the thermal shape fluctuation model (TSFM). The rise of GDR width with temperature also supports the assumptions of adiabatic coupling in the TSFM. But the GDR widths and corresponding reduced plots with $J$ are not consistent with those of the theoretical model at high spins.

There are various different definitions for the triaxial deformation parameter “γ”. It is pointed out that the parameter conventionally used in the Nilsson (or Woods-Saxon) potential, $\gamma (\mathrm{pot}:\mathrm{Nils})$ [or $\gamma (\mathrm{pot}:\mathrm{WS})]$, is not appropriate for representing the triaxiality γ defined in terms of the intrinsic quadrupole moments. The difference between the two can be as large as a factor two in the case of the triaxial superdeformed bands recently observed in Hf and Lu nuclei, i.e., $\gamma (\mathrm{pot}:\mathrm{Nils})\approx {20}^{°}$ corresponds to $\gamma \approx {10}^{°}$. In our previous work, we studied the wobbling excitations in Lu nuclei using the microscopic framework of the cranked Nilsson mean-field and the random phase approximation. The most serious problem was that the calculated $B(E2)$ value is about factor two too small. It is shown that the origin of this underestimate can mainly be attributed to the small triaxial deformation parameter $\gamma \approx {10}^{°}$ that corresponds to $\gamma (\mathrm{pot}:\mathrm{Nils})\approx {20}^{°}$. If the same triaxial deformation parameter is used as in the analysis of the particle-rotor model, $\gamma \approx {20}^{°}$, the calculated $B(E2)$ gives correct magnitude of the experimental data.

The model, introduced in a previous paper, for the description of the octupole and quadrupole degrees of freedom in conditions close to axial symmetry, is applied to situations of shape phase transitions where the quadrupole amplitude can reach zero. The transitional nuclei ${}^{224,226}\mathrm{Ra}$ and ${}^{224}\mathrm{Th}$ are discussed in the frame of this model. Their level schemes can be reasonably accounted for by assuming a square-well potential in two dimensions. Electromagnetic transition amplitudes are also evaluated and compared with existing experimental data.

The evolution of the low-energy electromagnetic dipole response with the neutron excess is investigated along the Sn isotopic chain within an approach incorporating Hartree-Fock-Bogoljubov (HFB) and multiphonon quasiparticle-phonon model (QPM) theory. General aspects of the relationship of nuclear skins and dipole sum rules are discussed. Neutron and proton transition densities serve to identify the pygmy dipole resonance (PDR) as a generic mode of excitation. The PDR is distinct from the GDR by its own characteristic pattern given by a mixture of isoscalar and isovector components. Results for the ${}^{100}\mathrm{Sn}$-${}^{132}\mathrm{Sn}$ isotopes and the several $N=82$ isotones are presented. In the heavy Sn isotopes the PDR excitations are closely related to the thickness of the neutron skin. Approaching ${}^{100}\mathrm{Sn}$ a gradual change from a neutron to a proton skin is found and the character of the PDR is changed correspondingly. A delicate balance between Coulomb and strong interaction effects is found. The fragmentation of the PDR strength in ${}^{124}\mathrm{Sn}$ is investigated by multiphonon calculations. Recent measurements of the dipole response in ${}^{130,132}\mathrm{Sn}$ are well reproduced.

Making use of the finite rank separable approach for the quasiparticle random phase approximation enables one to perform nuclear structure calculations in very large two-quasiparticle spaces. The approach is extended to take into account the residual particle-particle interaction. The calculations are performed by using Skyrme interactions in the particle-hole channel and density-dependent zero-range interactions in the particle-particle channel. To illustrate our approach, we study the properties of the lowest quadrupole states in the even-even nuclei ${}^{128}\mathrm{Pd}$, ${}^{130}\mathrm{Cd}$, ${}^{124-134}\mathrm{Sn}$, ${}^{128-136}\mathrm{Te}$, and ${}^{136}\mathrm{Xe}$.

Simultaneous ${\chi }^2$ analyses are performed for elastic scattering and fusion cross section data for the ${}^{12}\mathrm{C}+{}^{208}\mathrm{Pb}$ system at near-Coulomb-barrier energies by using the extended optical model approach in which the polarization potential is decomposed into direct reaction (DR) and fusion parts. Use is made of the double folding potential as a bare potential. It is found that the experimental elastic scattering and fusion data are well reproduced without introducing any normalization factor for the double folding potential and also that both DR and fusion parts of the polarization potential determined from the ${\chi }^2$ analyses satisfy separately the dispersion relation. Furthermore, it is shown that the imaginary parts of both DR and fusion potentials at the strong absorption radius change very rapidly, which results in a typical threshold anomaly in the total imaginary potential as observed with tightly bound projectiles such as α-particle and ${}^{16}\mathrm{O}$.

A method to calculate the nuclear double beta decay ($2\nu \beta \beta$ and $0\nu \beta \beta$) amplitudes within the continuum quasiparticle random phase approximation (cQRPA) is formulated. Calculations of the $\beta \beta$ transition amplitudes within the cQRPA are performed for ${}^{76}\mathrm{Ge}$, ${}^{100}\mathrm{Mo}$, and ${}^{130}\mathrm{Te}$. A rather simple nuclear Hamiltonian consisting of a phenomenological mean field and a zero-range residual particle-hole and particle-particle interaction is used. The calculated $2\nu \beta \beta$ amplitudes are almost unaffected when the single-particle continuum is taken into account, whereas we find a regular suppression of the $0\nu \beta \beta$ amplitudes that can be associated with additional ground-state correlations owing to collective states in the continuum. It is expected that inclusion of nucleon pairing in the single-particle continuum will somewhat compensate this suppression.

Exotic cluster decay of very heavy nuclei was studied in the microscopic Super-Asymmetric Fission Model. The Relativistic Mean Field model with the force FSU Gold was employed to obtain the densities of the cluster and the daughter nuclei. The microscopic nuclear interaction DDM3Y1, which has an exponential density dependence, and the Coulomb interaction were used in the double folding model to obtain the potential between the cluster and the daughter. Half-life values were calculated in the WKB approximation and the spectroscopic factors were extracted. The latter values are seen to have a simple dependence of the mass of the cluster as has been observed earlier. Predictions were made for some possible decays.