Using recent experimental information on the ${\beta }^{+}$ decay of ${}^{71}\mathrm{Kr},$ as well as available data on ${}^{71}\mathrm{Br},$ we suggest the deformation and relevant one-particle orbitals of low-lying states in the $A=71\mathrm{}$ nuclei. Prolate deformation and a weaker spin-orbit potential are suggested in order to be consistent with available data on ${}^{71}\mathrm{Br}.$

The $\Delta I=4\mathrm{}$ bifurcation in three identical superdeformed rotational bands is compared with predictions from the model of Hamamoto and Mottelson. A complete calculation of the tunneling amplitude in a semiclassical treatment of this model constrains the model’s parameters to just three regimes, with very different energy scales.

A generalization of Levinson’s theorem, relating the phase shift at zero energy to the number of bound states of the system, previously formulated to apply to the single-channel multiparticle scattering of a particle by a neutral system [L. Rosenberg and L. Spruch, Phys. Rev. A 54, 4978 (1996)] is further generalized to allow for multichannel scattering. An application to neutron-proton scattering with tensor forces leads to an extension of the existing version of Levinson’s theorem for this system by providing information on each of the eigenphases at zero energy rather than just their sum. The effect of the Pauli principle on the absolute determination of the phase shift is illustrated with applications of the method to the scattering of neutrons and protons by deuterons.

Based upon the Bonn meson-exchange model for the nucleon-nucleon $\mathrm{}\left(\mathrm{NN}\right)\mathrm{}$ interaction, we study systematically the charge-symmetry-breaking (CSB) of the $\mathrm{NN}$ interaction due to nucleon mass splitting. Particular attention is paid to CSB generated by the $2\pi$-exchange contribution to the $\mathrm{NN}$ interaction, $\pi \rho$ diagrams, and other multimeson exchanges. We calculate the CSB differences in the ${}^1{S}_0$ effective range parameters as well as phase shift differences in $S,$ $P,$ and higher partial waves up to 300 MeV laboratory energy. We find a total CSB difference in the singlet scattering length of 1.6 fm which explains the empirical value accurately. The corresponding CSB phase-shift differences are appreciable at low energy in the ${}^1{S}_0$ state. In the other partial waves, the CSB splitting of the phase shifts is small and increases with energy, with typical values in the order of $0.1°$ at 300 MeV in $P$ and $D$ waves.

We solve the coordinate space Faddeev equations in the continuum. We employ hyperspherical coordinates and provide analytical expressions allowing easy computation of the effective potentials at distances much larger than the ranges of the interactions where only $s$ waves in the different Jacobi coordinates couple. Realistic computations are carried out for the Borromean halo nuclei ${}^6\mathrm{He}\hspace{0.5em}(n+n+\alpha )$ for $J^{\pi }{=0\mathrm{}}^{\pm }{,1\mathrm{}}^{\pm }{,2\mathrm{}}^{\pm }$ and ${}^{11}\mathrm{Li}\hspace{0.5em}{(n+n+}^9\mathrm{Li})$ for ${\frac{1}{2}}^{\pm },$ ${\frac{3}{2}}^{\pm },$ ${\frac{5}{2}}^{\pm }.$ Ground state properties, strength functions, Coulomb dissociation cross sections, phase shifts, and complex $S$-matrix poles are computed and compared to available experimental data. We find enhancements of the strength functions at low energies and a number of low-lying $S$-matrix poles.

Five superdeformed (SD) bands have been observed in ${}^{149}\mathrm{Tb},$ using the Gammasphere spectrometer. The measurement was performed with a backed target to obtain lifetime information from a Doppler-shift attenuation method analysis. It is proposed that the yrast SD band corresponds to the ${}^{148}\mathrm{Gd}\left(\mathrm{yrast}\right)\otimes \pi 6^3$ intruder configuration. The first excited band (band 2) is found to be identical to the ${}^{150}\mathrm{Tb}$ yrast SD band. Band 3 is proposed to correspond to the $\pi \left[301\right]1/2(\alpha =-1/2)\to \left[651\right]3/2(\alpha =-1/2)$ proton-hole excitation coupled to the $\pi 6^4\nu 7^1\left(\nu \right[651]{1/2)}^{-1}$ intruder configuration. Bands 4 and 5, the weakest SD bands seen in the present work, show similarities with band 3 and are most likely associated with a similar intruder configuration.

High-spin states in the odd-$A{\hspace{0.5em}}^{113}\mathrm{Sn}$ nucleus have been investigated with the ${}^{100}\mathrm{Mo}{(}^{18}\mathrm{O},\hspace{0.5em}5n)$ reaction at 94 MeV using the Chalk River $8\pi$ array. Three decoupled $(\Delta I=2)$ rotational bands extending to spins $I$ in the range $(63/2\mathrm{}–69/2)ħ$ have been identified and connected to known low-lying states. Experimental observations for the most extended band have been interpreted as evidence for smooth band termination. Theoretical calculations performed within a configuration-dependent shell-correction approach suggest that all three bands are built upon deformed two-particle–two-hole proton excitations across the $Z=50\mathrm{}$ shell gap.

The gamma-decay of excited states in the $T_z=\frac{1}{2}$ nucleus ${}^{79}\mathrm{Y}$ has been observed in the ${}^{54}\mathrm{Fe}{(}^{28}\mathrm{Si}{,1p2n)}^{79}\mathrm{Y}$ reaction using the PEX array at the NBI Tandem Accelerator Laboratory. Four seven-element encapsulated cluster germanium detectors were operated in coincidence with a charged-particle ball and neutron wall. The transitions assigned to ${}^{79}\mathrm{Y}$ are proposed to form a ${K=5/2\mathrm{}}^{+}$ band analogous to that in ${}^{77}\mathrm{Sr},$ and the ${\mathcal{J}}^{\mathrm{}\left(1\right)\mathrm{}}$ moments of inertia are found to be extremely similar. Comparison is drawn between the rotational character of ${}^{79}\mathrm{Y}$ and neighboring Rb and Sr isotopes, in which identical bands have been observed.

Excited states in ${}^{180}\mathrm{Ta}$ have been identified using the ${}^{176}\mathrm{Yb}{(}^{11}\mathrm{B},\alpha {3n)}^{180}\mathrm{Ta}$ and ${}^{176}\mathrm{Yb}{(}^7\mathrm{Li}{,3n)}^{180}\mathrm{Ta}$ reactions and associated time-correlated $\gamma$-ray spectroscopy, including particle-$\gamma$ coincidences for channel selection. As well as identifying the rotational band based on the $9^{-}$ two-quasiparticle state at 75 keV, at least eight other low-lying two-quasiparticle states and associated rotational bands have been established. Lifetimes in the few nanosecond region were isolated using $\gamma -\gamma$-time techniques. Most of the observed two-quasiparticle states and some of the band members can be identified with states known from particle transfer studies. The properties of the observed ${\Omega }_n\pm {\Omega }_p$ partners of $1^{+}$ and $8^{+}$ bands from the $\nu {9/2}^{+}\left[624\right]\otimes \pi {7/2}^{+}\left[404\right]$ configuration and the $0^{-}$ and $9^{-}$ pair from the $\nu {9/2}^{+}\left[624\right]\otimes \pi {9/2}^{-}\left[514\right]$ configuration are discussed. High-$K$ structures identified include the band based on the four-quasiparticle $45\hspace{0.5em}\mu \mathrm{s}$, ${15}^{-}$ isomer, a 32 ns, four-quasiparticle ${18}^{\mathrm{}(+)\mathrm{}}$ isomer, and a six-quasiparticle ${19}^{\left(-\right)}$ intrinsic state and its band. Configuration assignments are aided by analysis of the in-band decay properties, which confirm, for example, a predominantly $\nu {\pi }^3$ configuration for the ${15}^{-}$ isomer. The results are compared with multiquasiparticle calculations. A number of yrast high-$K$ six- and eight-quasiparticle states which could be accessible in future studies are predicted.

The position of the two-proton drip line has been calculated for even-even nuclei with $10<~Z<~82$ in the framework of the relativistic mean-field (RMF) theory. The current model uses the NL3 effective interaction in the mean-field Lagrangian and describes pairing correlations in the Bardeen-Cooper-Schrieffer (BCS) formalism. The predictions of the RMF theory are compared with those of the Hartree-Fock+BCS approach (with effective force Skyrme SIII) and the finite-range droplet model (FRDM) and with the available experimental information.

The damping rate of hot giant dipole resonances (GDRs) is investigated. Besides Landau damping we consider collisions and density fluctuations as contributions to the damping of GDRs. Within the nonequilibrium Green’s function method we derive a non-Markovian kinetic equation. The linearization of the latter one leads to complex dispersion relations. The complex solution provides the centroid energy and the damping width of giant resonances. The experimental damping widths are the full width half maximum and can be reproduced by the full width of the structure function. Within simple finite size scaling we give a relation between the minimal interaction strength which is required for a collective oscillation and the cluster size. We investigate the damping of giant dipole resonances within a Skyrme type of interaction. Different collision integrals are compared with each other in order to incorporate correlations. The inclusion of a conserving relaxation time approximation allows us to find the $T^2$ dependence of the damping rate with a temperature known from Fermi-liquid theory. However, memory effects turn out to be essential for a proper treatment of the damping of collective modes. We derive a Landau-like formula for the one-particle relaxation time similar to the damping of zero sound.

The interplay between the quadrupole-quadrupole and spin-orbit interactions in nuclei is analyzed in an SU(3) basis. Results for two $\mathrm{ds}$-shell nuclei ${}^{20}\mathrm{Ne}$ and ${}^{22}\mathrm{Ne}$ and one $\mathrm{fp}$-shell nucleus ${}^{44}\mathrm{Ti}$ are considered for realistic values of the strength parameters of these two interactions. The ground state band is built from the $S=0\mathrm{}$ leading irreducible representation (irrep), which mixes strongly with the leading $S=1\mathrm{}$ irreps in the proton and neutron subspaces. The quadrupole-quadrupole interaction is found to give dominant weights to the “stretched” coupled representations, which supports a strong truncation of the Hilbert space.

Octupole states have been studied systematically in the deformed actinide nuclei ${}^{230}\mathrm{Th},$ ${}^{234,236,238}\mathrm{U},$ ${}^{240}\mathrm{Pu},$ ${}^{246}\mathrm{Cm},$ and ${}^{250}\mathrm{Cf}$ using the interacting boson approximation 1. Parameters for the positive parity cores were set by reproducing data from the ground state and γ-vibration bands with the extended consistent-$Q$ formalism. A prescription for setting the parameter ${\epsilon }_f$ systematically was adopted for the calculations of the octupole bands. The ordering of the $K^{\pi }{=0\mathrm{}}^{-},$ $1^{-},$ and $2^{-}$ bands and the behavior of many $E1\mathrm{}$ and $E3\mathrm{}$ transitions are well reproduced with a narrow range of parameters, particularly when the existence of a $N=164\mathrm{}$ subshell gap is assumed. It is predicted that in ${}^{246}\mathrm{Cm}$ and ${}^{250}\mathrm{Cf}$ the $K^{\pi }{=3\mathrm{}}^{-}$ octupole states built on the ground state are located above 6 MeV and are strongly fragmented.

The Doppler shift attenuation method was used to determine lifetimes in the picosecond region for excited states of ${}^{117}\mathrm{Sb}$ populated with the $(\alpha ,2n\gamma )$ reaction at $E_{\alpha }=27.2\mathrm{}\mathrm{MeV}.$ Interacting boson-fermion model calculations explain reasonably well the main features of the positive parity levels known up to about 2.5 MeV excitation. The mixing of the lowest one-quasiparticle ${9/2}^{+}$ state with the intruder $\mathrm{}(2p-1h)\mathrm{}$ ${9/2}^{+}$ state, as well as the quadrupole deformation of the intruder band are also discussed.

The dynamic-correlation model (DCM) has been used to calculate the ground-state hyperfine splitting in hydrogenlike ions characterized by core nuclei with one valence neutron or proton hole. For such nuclei the DCM nonperturbatively couples the single hole to the collective states of the reference closed-shell core. Within this nuclear model the magnetic moments, the nuclear radii, and the quadrupole moments of the ground states are well reproduced. The hyperfine splittings of ${}^{165}{\mathrm{Ho}}^{66+},$ ${}^{185}{\mathrm{Re}}^{74+},$ ${}^{187}{\mathrm{Re}}^{74+},$ and ${}^{207}{\mathrm{Pb}}^{81+}$ are calculated from the derived configuration-mixing amplitudes. In all cases a very good agreement with measured values is obtained.

In the single-state-dominance hypothesis (SSDH) the decay rate of the two-neutrino double-β decay to the final ground state is solely determined by virtual single-β-decay transitions via the $1^{+}$ ground state of the intermediate nucleus. A very important consequence the SSDH will be that some of nonaccelerator measurements of double-β-decay observables could be circumvented by single-β-decay measurements. To assess the validity of the SSDH, we have carried out a theoretical analysis of all double-β-decay transitions where the spin-parity of the ground-state of the intermediate nucleus is $1^{+}$. The calculations indicate that the double-electron emitters, as well as the less explored double-positron emitters, show evidence of the SSDH.

We consider the pairing-plus-quadrupole model Hamiltonian within the framework of a many-fermion shell model. The Hamiltonian exhibits a transition from a superconducting to a rotational phase with variation of a parameter. The model has analytical solutions in its two limits due to the presence of dynamical symmetries. However, the symmetries are basically incompatible with one another which means that no simple solution exists in intermediate situations. Exact (numerical) solutions are nevertheless possible on a computer and enable one to study the behavior of competing but incompatible symmetries and the phase transitions that result in a semirealistic situation. This mixed-symmetry dynamics generates a rich structure which gives new insight for the study of phase transitions.

The photoproduction of a Λ on ${}^{12}\mathrm{C}$ is investigated by using the recently developed Saclay-Lyon amplitudes for the $\gamma \overrightarrow{p}{K}^{+}\Lambda$ reaction and the single-particle wave functions from a relativistic mean-field model of nuclei and Λ hypernuclei. With the nuclear transition matrix elements taken from a shell-model calculation, the predicted bound-Λ production cross sections are close to the ${}^{12}\mathrm{C}(\gamma {,K}^{+}{)}_{\Lambda }^{12}\mathrm{B}$ reaction data. The dependence of the predictions on the model of $\gamma \overrightarrow{p}{K}^{+}\Lambda$ amplitudes has been investigated. The cross sections of quasifree processes leading to an unbound Λ are also calculated in a simple three-body model. The predicted cross sections of the inclusive ${}^{12}\mathrm{C}\left(\gamma {,K}^{+}\right)$ reaction reproduce the energy dependence of the data up to 1.1 GeV, but overestimate the magnitude by a factor of about 2.2. We discuss the extent to which this overestimation can be understood in terms of medium effects on the propagation of the outgoing $K^{+}$ and Λ.

Double-differential cross sections for $62.7\pm 1.0$ MeV neutron-induced light charged particle $(p$, $d$, $t$, and $\alpha )$ production on aluminum are reported. Angular distributions were measured at laboratory angles between $20°$ and $160°$ in steps of $10°$. Procedures for data taking and data reduction are described. Results for double-differential, energy-differential, and total production cross sections are presented. The measurements are compared to existing proton-induced data and to nuclear model calculations which include preequilibrium and equilibrium decay mechanisms. Agreement with the model calculations is good for all ejectile types except for deuterons, where pickup processes are overestimated. The neutron-induced data presented are shown to be in good agreement with experimental proton-induced data for charge-symmetric reaction channels. For the proton emission channel the approximate factor of two between the two emission spectrum measurements is explained.

A study of the ${}^{12}{\mathrm{C}(}^{20}{\mathrm{N}\mathrm{e},\mathrm{}}^{16}{\mathrm{O}\mathrm{}}^8{\mathrm{B}\mathrm{e})}^8\mathrm{Be}$ and ${}^{12}{\mathrm{C}(}^{24}{\mathrm{M}\mathrm{g},\mathrm{}}^{16}{\mathrm{O}\mathrm{}}^8{\mathrm{B}\mathrm{e})}^{12}\mathrm{C}$ reactions has revealed ${}^{16}{\mathrm{O}+}^8\mathrm{Be}$ breakup occurring from specific states in the ${}^{24}\mathrm{Mg}$ nucleus at high-excitation energies. A spin assignment has been determined for one of these states from an angular correlation measurement of the breakup fragments. In the ${}^{20}\mathrm{Ne}$ beam reaction, states have been identified at 22.33, 22.96, 24.00, 24.43, 24.88, 25.53, 27.35, 27.97, 28.88, and 30.13 MeV, and in the ${}^{24}\mathrm{Mg}$ beam reaction states have been identified at 20.58, 21.54, 22.70, and 24.31 MeV. The results have been compared with previous measurements of the ${}^{12}{\mathrm{C}+}^{12}\mathrm{C}$ breakup channel.