The rate for the photon emission accompanying orbital 1S electron capture by the atomic nucleus is recalculated. While a photon can be emitted by the electron or by the nucleus, the use of the length gauge significantly suppresses the nuclear contribution. Our calculations resolve the long standing discrepancy of theoretical predictions with experimental data for $\Delta J=2$ forbidden transitions. We illustrate the results by comparison with the data established experimentally for the first forbidden unique decays of ${}^{41}\mathrm{Ca}$ and ${}^{204}\mathrm{Tl}$.

Differential cross section of the inelastic scattering of a 54 MeV/nucleon ${}^{26}\mathrm{Ne}$ beam on a lead target has been measured by detecting the deexcitation γ-rays. Analysis of the first $2^{+}$ state angular distribution of the inelastically scattered nuclei shows that the process cannot be considered as a pure Coulomb excitation, and nuclear contribution must be taken into account. The charge deformation deduced, ${\beta }_2^C=0.392\pm 0.024$, corresponds to a $B(E2)=141\pm 18e^2{\mathrm{fm}}^2$ in agreement with a $N=16$ subshell closure.

We calculate the nuclear matrix elements of the neutrinoless double beta ($0\nu \beta \beta$) decays of ${}^{76}\mathrm{Ge}$ and ${}^{82}\mathrm{Se}$ for the light neutrino exchange mechanism. The nuclear wave functions are obtained by using realistic two-body forces within the proton-neutron quasiparticle random-phase approximation (pnQRPA). We include the effects that come from the finite size of a nucleon, from the higher-order terms of nucleonic weak currents, and from the nucleon-nucleon short-range correlations. Most importantly, we improve on the presently available calculations by replacing the rudimentary Jastrow short-range correlations by the more advanced unitary correlation operator method (UCOM). The UCOM-corrected matrix elements turn out to be notably larger in magnitude than the Jastrow-corrected ones. This has drastic consequences for the detectability of $0\nu \beta \beta$ decay in present and future double beta experiments.

The isovector giant and pygmy dipole resonances in even-even Ni isotopes are studied within the framework of a fully consistent relativistic random-phase approximation built on the relativistic mean field ground state. An additional isoscalar-isovector nonlinear coupling term is adopted in the standard effective mean field Lagrangian, which could modify the density dependence of the symmetry energy and soften the symmetry energy at the saturation density without changing the agreement with experimentally existing data of ground state properties. We found that the centroid energy of the isovector giant dipole resonance is tightly correlated to the neutron skin thickness. In contrast, the centroid energy of the isovector pygmy resonance is insensitive to the density dependence of the symmetry energy by tuning the isoscalar-isovector nonlinear coupling.

Gamma rays populating the α-decaying isomeric state in ${}^{169}\mathrm{Ir}$ have been observed for the first time. The experiment employed the recoil-decay tagging method using the JUROGAM γ-ray spectrometer, the RITU gas-filled recoil separator and the GREAT spectrometer located at the RITU focal plane. The γ-ray cascade feeding the isomeric α-decaying state exhibits a rotational structure consistent with a $h_{11/2}$ proton coupled to a triaxially deformed core. The experimental results are compared with predictions from total Routhian surface calculations.

To date, the possible effects of coupling to nucleon transfer reactions on the elastic scattering and fusion of weakly bound exotic nuclei have been largely neglected. The ${}^{15}\mathrm{C}$ nucleus presents a virtually unique opportunity to test these effects for an almost pure s${}_{1/2}$ single neutron halo nucleus. We present a series of coupled reaction channel calculations of the sub-barrier elastic scattering and single neutron transfer reactions, plus near-barrier excitation functions of the total fusion cross section for the ${}^{12}\mathrm{C}$, ${}^{13}\mathrm{C}$, and ${}^{15}\mathrm{C}+{}^{208}\mathrm{Pb}$ systems. The method is validated against data for ${}^{12}\mathrm{C}$ and ${}^{13}\mathrm{C}+{}^{208}\mathrm{Pb}$. A large effect on the sub-barrier elastic scattering due to coupling to the (${}^{15}\mathrm{C}$,${}^{14}\mathrm{C}$) single neutron stripping reaction is found, ascribed to the 2s${}_{1/2}$ halo nature of the ${}^{15}\mathrm{C}$ ground state, in contrast to the two stable carbon isotopes. We also find a significant diminution of the above barrier total fusion cross section for ${}^{15}\mathrm{C}$ due to this coupling, again in contrast to the stable isotopes.

With a high energy-resolution of $\Delta E=21$ keV in the ${}^{34}\mathrm{S}$(${}^3\mathrm{He}$$,t$)${}^{34}\mathrm{Cl}$ measurement at $0°$ and at 140 MeV/nucleon, strengths of Fermi and Gamow-Teller (GT) transitions between $T_z=+1$ and $T_z=0$ states were studied, where $T_z$ is the $z$ component of isospin $T$. The corresponding isospin-symmetric transitions connecting $T_z=-1$ and $T_z=0$ states can be studied in the ${}^{34}\mathrm{Ar}$ ${\beta }^{+}$ decay. The strengths of corresponding GT transitions were compared up to the excitation energy ($E_x$) of 3.1 MeV. A good agreement was observed for the two strong transitions to states around $E_x=3$ MeV, while a disagreement of 40% was observed for a weaker transition to a low-lying state.

The quasiparticle time blocking approximation (QTBA) is presented as a model for the description of natural-parity excitations in open-shell nuclei. Most attention is paid to the question of the damping of the giant dipole resonance. Within the model pairing correlations, two-quasiparticle ($2q$), and $2q\otimes$phonon configurations are included. Thus the QTBA is an extension of the quasiparticle random phase approximation to include quasiparticle-phonon coupling. Calculational formulas are presented for the case of neutral natural-parity excitations in spherical nuclei. The main equations are written in the coordinate representation that allows to take into account single-particle continuum completely. The QTBA is applied to describe $E1$ photoabsorption cross sections in nuclei ${}^{116,120,124}\mathrm{Sn}$. It has been obtained that the $2q\otimes$phonon configurations provide noticeable fragmentation of the giant dipole resonance resulting in the appearance of a significant spreading width. The results are compared with available experimental data.

Excited states in the ${}^{138}\mathrm{I}$ nucleus, including $T_{1/2}=1.3$ $\mu s$ isomer decaying by a stretched $E2$ transition of 68 keV, were observed for the first time. The ${}^{138}\mathrm{I}$ nucleus was populated in the spontaneous fission of ${}^{248}\mathrm{Cm}$ and studied by means of prompt γ-ray spectroscopy using the EUROGAM 2 array. The microsecond isomer was populated in the neutron-induced fission of ${}^{235}\mathrm{U}$ and observed at the LOHENGRIN separator. Excitation scheme consists of a low-spin part and a medium-spin, $\Delta I=1$, band based on the $7^{-}$ state with the $(\pi g_{7/2}\nu f_{7/2}){}_{7^{-}}$ dominating configuration, as predicted by the shell model. The shell-model calculations of ${}^{138}\mathrm{I}$ provide the optimum reproduction of the experimental scheme when the $\pi d_{5/2}$ orbital is lowered by 600 keV relative to its position in ${}^{133}\mathrm{Sb}$. In the calculation the isomeric level has spin and parity $3^{-}$ and deexcites by an $E2$ isomeric transition to the $1^{-}$ level, located only 9 keV above the predicted $0^{-}$ ground state. Considering additional information on the ground-state spin from the literature, we propose that in ${}^{138}\mathrm{I}$ the $1^{-}$ level corresponds to the ground state and the $0^{-}$ is located above. We note, however, that additional measurements are required to resolve this problem.

The sensitivity of elastic breakup to the interior of the projectile wave function is analyzed. Breakup calculations of loosely bound nuclei (${}^8\mathrm{B}$ and ${}^{11}\mathrm{Be}$) are performed with two different descriptions of the projectile. The descriptions differ strongly in the interior of the wave function, but exhibit identical asymptotic properties, namely the same asymptotic normalisation coefficient, and phase shifts. Breakup calculations are performed at intermediate energies (40–70 MeV/nucleon) on lead and carbon targets as well as at low energy (26 MeV) on a nickel target. No dependence on the projectile description is observed. This result confirms that breakup reactions are peripheral in the sense that they probe only the external part of the wave function. These measurements are thus not directly sensitive to the total normalization of the wave function, i.e., spectroscopic factor.

A recently discovered resonance at 193 keV determines the thermonuclear rates of the ${}^{17}\mathrm{O}$ $+p$ reactions at temperatures important for the nucleosynthesis in classical novae ($T=0.1-0.4$ GK). We report on a remeasurement of this resonance in the ${}^{17}\mathrm{O}$($p,\alpha$)${}^{14}\mathrm{N}$ reaction by using a different kind of target compared to the previous study. Special emphasis is placed on Monte Carlo simulations of the experiment in order to better understand certain effects that have been disregarded previously. Our measured value of the resonance strength amounts to $(\omega \gamma ){}_{p\alpha }=(1.66\pm 0.17)\times {10}^{-3}$ eV, in agreement with the previously reported result. As a byproduct of our study, we find that the inhomogeneity of the foil placed in front of the α-particle detector determines the resolution in the pulse-height spectrum, and thus constrains the signal-to-noise ratio in searches of very weak ($p,\alpha$) resonances.

Knowledge of the ${}^{18}\mathrm{F}$($p,\alpha$)${}^{15}\mathrm{O}$ and ${}^{18}\mathrm{F}$($p,\gamma$)${}^{19}\mathrm{Ne}$ astrophysical reaction rates are important to understand γ-ray emission from nova explosions and heavy-element production in x-ray bursts. The rates for these reactions have been uncertain, in part due to a lack of a comprehensive examination of the available structure information in the compound nucleus ${}^{19}\mathrm{Ne}$. We have examined the latest experimental measurements with radioactive and stable beams, collected all the structure information in the nucleus ${}^{19}\mathrm{Ne}$ and its mirror ${}^{19}\mathrm{F}$, and made estimates of unmeasured ${}^{19}\mathrm{Ne}$ nuclear-level parameters. These parameters will be useful for future reaction rate calculations.

Neutron-neutron quasifree scattering in the $\mathit{nd}$ breakup reaction at 25 MeV has been investigated. The absolute cross section was determined with an accuracy of a few percentages, normalized by $\mathit{np}$ scattering, which was measured simultaneously. The data were analyzed by detailed Monte Carlo simulations based on rigorous 3N Faddeev-type calculations using the CD-Bonn $\mathit{NN}$ potential. The measured cross-section data in this experiment are (16.0 ± 4.6)% larger than the theoretical predictions.

It has been shown recently that a simple formula in terms of the valence nucleon numbers and the mass number can describe the essential trends of excitation energies of the first $2^{+}$ states in even-even nuclei. By evaluating the first order energy shift due to the zero-range residual interaction, we find that the factor which reflects the effective particle number participating in the interaction from the Fermi orbit governs the main dependence of the first $2^{+}$ excitation energy on the valence nucleon numbers.

In jet quenching, a hard QCD parton, before fragmenting into a jet of hadrons, deposits a fraction of its energy in the medium, leading to suppressed production of high-$p_T$ hadrons. The process can generate shock waves. We study the distortion of Mach shock waves due to jet quenching in central Au+Au collisions and its effect on particle production. Finite fluid velocity and inhomogeneity of the medium can distort the Mach shock front significantly such that the inside shock front disappear and the outside shock front is opened up. We also show that the STAR data on azimuthal distribution of background subtracted secondaries, associated with high $p_T$ trigger, are reasonably well explained by the excess pions produced due to partonic energy loss.

This paper demonstrates the feasibility of quadrupole moment measurements on isomeric levels populated in projectile fragmentation reactions. The neutron-rich ${}^{61}\mathrm{Fe}$$(9/2^{+})$ [$E^{*}=$ 861 keV, $T_{1/2}=$ 239(5) ns] isomer was produced and spin aligned by the intermediate energy fragmentation of a ${}^{64}\mathrm{Ni}$ beam and implanted in a Cd single crystal. Its spectroscopic quadrupole moment $\left|Q_s\right|=41(6)e{\mathrm{fm}}^2$ agrees with mean-field based calculations using the finite-range Gogny force, suggesting a moderately deformed shape characterized by an intrinsic charge quadrupole moment $Q_0=-85e{\mathrm{fm}}^2$ or $Q_0=+115e{\mathrm{fm}}^2$. The present measurement paves the way for future determinations of isomeric quadrupole moments in more exotic nuclei.

A study of the $\mathit{pd}\to pd\eta$ reaction in the energy range where the recent data from Uppsala are available is done in the two-step model of η production including the final state interaction. The $\eta -d$ final state interaction is incorporated through the solution of the Lippmann Schwinger equation using an elastic scattering matrix element, $T_{\eta d\to \eta d}$, which is required to be half off-shell. It is written in a factorized form, with an off-shell form factor multiplying an on-shell part given by an effective range expansion up to the fourth power in momentum. The parameters of this expansion have been taken from an existing recent relativistic Faddeev equation solution for the $\eta \mathit{NN}$ system corresponding to different $\eta -N$ scattering amplitudes. Calculations have also been done using few body equations within a finite rank approximation to generate $T_{\eta d\to \eta d}$. The $p-d$ final state interaction is included in the spirit of the Watson-Migdal prescription by multiplying the matrix element by the inverse of the Jost function. The $\eta -d$ interaction is found to be dominant in the region of small invariant $\eta -d$ mass, $M_{\eta d}$. The $p-d$ interaction enhances the cross section in the whole region of $M_{\eta d}$, but is larger for large $M_{\eta d}$. We find nearly isotropic angular distributions of the proton and the deuteron in the final state. All the above observations are in agreement with the data. The production mechanism for the entire range of the existing data on the $pd\to \mathit{pd}\eta$ reaction seems to be dominated by the two-step model of η production.

High spin properties of the neutron-deficient ${}^{66-72}\mathrm{Ge}$ isotopes have been studied using the projected shell model approach. In particular, backbending phenomena, $B(E2)$ transition probabilities, and $g$ factors are investigated for these isotopes along the yrast line.

Band structure and electromagnetic transition properties of the low-lying states in the $N=Z$ ${}^{68}\mathrm{Se}$ nucleus were studied within the framework of interacting boson model 3. The isospin excitation states with $T>T_Z$ are identified. The $M$1 and $E$2 matrix elements for low-lying states have been investigated and were used to identify the low-lying mixed symmetry states. Special attention is given to the occurrence of $0_2^{+}$ state, recently predicted by the projected shell-model (PSM) calculation. The present predicted spectrum for ${}^{68}\mathrm{Se}$ is close to the recent PSM results and confirms the results for the $0_2^{+}$ state. The calculated results are compared with available experimental data, and they are in general good agreement.

Large-scale shell-model calculations, with dimensions reaching ${10}^9$, are carried out to describe the recently observed deformed (ND) and superdeformed (SD) bands based on the first and second excited $0^{+}$ states of ${}^{40}\mathrm{Ca}$ at 3.35 and 5.21 MeV, respectively. A valence space comprising two major oscillator shells, $\mathit{sd}$ and $\mathit{pf}$, can accommodate most of the relevant degrees of freedom of this problem. The ND band is dominated by configurations with four particles promoted to the $\mathit{pf}$ shell (4p-4h in short). The SD band by 8p-8h configurations. The ground state of ${}^{40}\mathrm{Ca}$ is strongly correlated, but the closed shell still amounts to 65%. The energies of the bands are very well reproduced by the calculations. The out-band transitions connecting the SD band with other states are very small and depend on the details of the mixing among the different $n\mathrm{p}\text{−}n\mathrm{h}$ configurations; in spite of that, the calculation describes them reasonably. For the in-band transition probabilities along the SD band, we predict a fairly constant transition quadrupole moment $Q_0(t)~170e$ fm${}^2$ up to $J=10$ that decreases toward the higher spins. We submit also that the $J=8$ states of the deformed and superdeformed bands are maximally mixed.