High-spin states in ${}_{}{}^{109,111}{}_{}{}^{}\mathrm{Cd}$ have been investigated with the reaction ${}_{}{}^{96}{}_{}{}^{}\mathrm{Zr}$${(}^{18}$O,xn${)}^{114\mathrm{-}\mathit{x}}$Cd at beam energies of 60 and 70 MeV. The decoupled yrast bands observed in both nuclei are interpreted as being built upon a low-Kh11/2-quasineutron configuration. Both structures exhibit band crossings corresponding to the rotational alignment of a pair of h11/2 quasineutrons. Two positive-parity bands built on a g7/2-quasineutron configuration are observed in ${}_{}{}^{109}{}_{}{}^{}\mathrm{Cd}$. These exhibit a signature inversion in the region of the first (ν${\mathit{h}}_{11/2)}^2$ alignment. This may be associated with some softness to triaxiality. The results are discussed in terms of the cranked shell model, total Routhian surface calculations, and the systematics of neighboring nuclei.

High spin states in the neutron deficient isotopes ${}_{}{}^{90}{}_{}{}^{}\mathrm{Ru}$ and ${}_{}{}^{91}{}_{}{}^{}\mathrm{Ru}$ have been studied in the 2p2n and 2pn exit channels of the reaction ${}_{}{}^{36}{}_{}{}^{}\mathrm{Ar}$${+}^{58}$Ni using the 149 MeV ${}_{}{}^{36}{}_{}{}^{}\mathrm{Ar}$ beam at VICKSI and the OSIRIS array. By gating the γγ coincidences with evaporated neutrons and protons, excited states in ${}_{}{}^{90}{}_{}{}^{}\mathrm{Ru}$ were identified for the first time and the level scheme of ${}_{}{}^{91}{}_{}{}^{}\mathrm{Ru}$ was extended. In both nuclei, the level energies and branching ratios follow the predictions of shell model calculations performed within the (1${\mathit{g}}_{9/2}$,2${\mathit{p}}_{1/2}$) single-particle space.

The presence of low-lying 1${\mathit{s}}_{1/2}$ virtual state in the n${+}^9$Li system, when included in Faddeev three-body calculations, has a pronounced effect on the structure of the ${}_{}{}^{11}{}_{}{}^{}\mathrm{Li}$ halo. The resulting ${}_{}{}^9{}_{}{}^{}\mathrm{Li}$ momentum distributions, calculated in the Serber model, have a narrow width comparable with the experimental data. The structure of ${}_{}{}^{11}{}_{}{}^{}\mathrm{Li}$ would then have nearly 50% of s-wave motion between the neutrons and the core. The three-body system may also approximately fulfill the conditions for the appearance of Efimov states, and there may exist low-lying excited states near the breakup threshold.

In this article, we consider a semiclassical stochastic mean-field approach. In the case of unstable infinite nuclear matter, we calculate the characteristic time of the exponential growing of fluctuations and the diffusion coefficients associated to the unstable modes, in the framework of the Boltzmann-Langevin theory. These two quantities are essential to describe the dynamics of fluctuations and instabilities since, in the unstable regions, the evolution of the system will be dominated by the amplification of fluctuations. In order to make realistic 3D calculations feasible, we suggest to replace the complicated Boltzmann-Langevin theory by a simpler stochastic mean-field approach corresponding to a standard Boltzmann evolution, complemented by a simple noise chosen to reproduce the dynamics of the most unstable modes. Finally we explain how to approximately implement this method by simply tuning the noise associated to the use of a finite number of test particles in Boltzman-like calculations.

The energy spectra and B(E2) values of the uranium isotopes ${}_{}{}^{232\mathrm{-}238}{}_{}{}^{}\mathrm{U}$ are calculated in the interacting-boson-plus-fermion-pair model. It was found that in order to reproduce the identical energy bands, weak boson pairing, a weak angular momentum interaction and a strong quadrupole interaction are needed.

Cluster decays of ${}_{}{}^{112\mathrm{-}120}{}_{}{}^{}\mathrm{Ba}$ nuclei are calculated within a preformed cluster model. The α-nuclei ${}_{}{}^4{}_{}{}^{}\mathrm{He}$, ${}_{}{}^8{}_{}{}^{}\mathrm{Be}$, ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, and ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ are predicted as the possible decay modes, lying within the limits of present experimental methods. Other than the α particle, ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ decay of ${}_{}{}^{112}{}_{}{}^{}\mathrm{Ba}$ is shown to be the most probable one with half-life time ${\mathit{T}}_{1/2}$∼${10}^4$ s, stressing the role of doubly magic ${}_{50}{}^{100}{}_{}{}^{}\mathrm{Sn}$ daughter nucleus in cluster radioactivity. The use of different Q values for ${\mathit{T}}_{1/2}$ estimates and presence of nuclear structure effects in Geiger-Nuttall plots are also discussed.

The photopion production of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$(γ,${\mathrm{\pi }}^{+}$${)}^3$H has been calculated by the distorted wave impulse approximation in order to include the final state interaction (FSI) between ${\mathrm{\pi }}^{+}$ and ${}_{}{}^3{}_{}{}^{}\mathrm{H}$. The optical potentials used to describe the FSI are the Stricker, McManus, and Carr potential and the Kim potential. The inclusion of the FSI improves significantly the theoretical estimations compared with the results of plane wave impulse approximation. In case of low momentum transfer the contribution of ${\mathit{E}}_1^{+}$(3/2) amplitude is shown to play an additional role in obtaining an agreement with the experimental results.

The Interacting Boson Approximation Model (IBA) has existed for nearly twenty years and has now entered the lexicon of standard nuclear models used to interpret data on low-energy nuclear structure. While most recognized for its symmetries and algebraic structure, the model has a number of other less-well-known but equally intrinsic properties which gave unavoidable, parameter-free predictions. Since these predictions cannot be altered and since they concern central aspects of low-energy nuclear collective structure, they provide a set of basic tests of the inherent framework of the model. This paper outlines these ‘‘robust’’ predictions and compares them with the data.

The response functions for the extended second and third random phase approximation are compared. A second-order perturbation calculation shows that the first-order amplitude for the direct 3p3h (three-particle–three-hole) excitation from the ground state cancels with those that are engendered by the 1p1h-3p3h coupling. As a consequence nonvanishing 3p3h effects to the 1p1h response involve off energy shell renormalization only. On shell 3p3h processes are absent.

The heat capacity for a system of nucleons as a function of temperature is determined from the canonical partition function, which is projected from an approximation to the grand canonical partition function. This approximation is obtained from a functional integral representation of the partition function, including both thermodynamic fluctuations and first order quantum corrections. The number projection methods include a simple contour integration of ‘‘Wick rotation’’, and a Chebyschev polynomial expansion, both of which are formally exact. The above procedure is tested in a simple ${\mathit{i}}_{13/2}$ pairing model for which the exact canonical and grand canonical results can be obtained. It is found that both number projection methods fail to predict the position or the height of the peak in the heat capacity due to errors in the approximation to the grand partition function, even though the path integral approximation is very good.

A Coulomb sum rule is derived for the response of nuclei to (e,e’) scattering with large three-momentum transfers. Unlike the nonrelativistic formulation, the relativistic Coulomb sum is restricted to spacelike four-momenta for the most direct connection with experiments; an immediate consequence is that excitations involving antinucleons, e.g., NN¯ pair production, are approximately eliminated from the sum rule. Relativistic recoil and Fermi motion of target nucleons are correctly incorporated. The sum rule decomposes into one- and two-body parts, with correlation information in the second. The one-body part requires information on the nucleon momentum distribution function, which is incorporated by a moment expansion method. The sum rule given through the second moment (RCSR-II) is tested in the Fermi gas model, and is shown to be sufficiently accurate for applications to data.

A systematics of thermal properties, for nuclei with 16≤A≤30, is presented. The study has been motivated by previous reports on phase transitions involving nuclei belonging to the 2s-1d shell. We have used the nuclear ${\mathrm{SU}}_3$ scheme to calculate the specific heat and the temperature dependence of the intrinsic quadrupole moment for each nuclei. We have found that finite size effects and not true phase transitions are affecting the temperature dependence of these quantities, at least within the ${\mathrm{SU}}_3$ scheme and for the nuclei which we have considered.

We calculate the effective mass of the ω meson in nuclear matter in a relativistic random-phase approximation to the Walecka model. The dressing of the meson propagator is driven by its coupling to particle-hole pairs and nucleon-antinucleon (NN¯) excitations. We report a reduction in the ω-meson mass of about 170 MeV at nuclear-matter saturation density. This reduction arises from a competition between the density-dependent (particle-hole) dressing of the propagator and vacuum polarization (NN¯ pairs). While density-dependent effects lead to an increase in the mass proportional to the classical plasma frequency, vacuum polarization leads to an even larger reduction caused by the reduced effective nucleon mass in the medium.

We evaluate the spreading width of the giant resonances using the discontinuity in the second derivative of the propagator of the vibrational phonon. This allows us to isolate the processes that contribute to the spreading width in terms of the Feynman diagrammatic expansion of the full boson propagator. Utilizing for classification purposes the nuclear field theory perturbative treatment of the one-phonon state, we obtain a very simple expression for the spreading width in the lowest (nonvanishing) order of perturbation theory.

We apply the Lee-Suzuki iteration method to calculate the linked-folded diagram series for a new Nijmegen local NN potential. We obtain an exact starting-energy-independent effective two-body interaction for a multishell, no-core, harmonic-oscillator model space. It is found that the resulting effective-interaction matrix elements can be well approximated by the Brueckner G-matrix elements evaluated at starting energies selected in a simply way. These starting energies are closely related to the energies of the initial two-particle states in the ladder diagrams. The ‘‘exact’’ and approximate effective interactions are used to calculate the energy spectrum of ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ in order to test the utility of the approximate form.

We study the isovector weak response of the core to an external perturbation using linear response theory in nuclear matter. We extend previous results to the kinematic region away from the long wavelength regime where the effects have been proven small. For the muon capture process we found a sizable quenching of the contribution of the induced pseudoscalar term. Applied to actual nuclei, however, the strong density dependence of the weak isovector response washes out the screening found at nuclear matter densities, slightly modifying muon capture rates.

In order to estimate octupole-induced E1 strength in very deformed nuclei we calculate their intrinsic dipole moments within the shell correction method. We use the formula for the macroscopic part of the dipole moment derived by Dorso, Myers, and Swiatecki, however, without approximation limiting its validity to small deformations. We obtain rather large dipole moments in superdeformed Hg and Pb nuclei, in agreement with recent Hartree-Fock calculations. This points to the possibility that in these nuclei interband E1 transitions may be detectable in spite of enormous competition of superdeformed intraband E2 transitions. We give also estimates for dipole moments of even more deformed systems.

Fusion, strongly damped, quasielastic and elastic scattering yields have been measured for the ${}_{}{}^{16,17,18}{}_{}{}^{}\mathrm{O}$${+}^{10,11}$B systems at 1 MeV≤E/A≤4 MeV and ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}$${+}^9$Be at 56 MeV. The significant yields observed for the strongly energy-damped products are attributed to a fusion-fission process. This identification is supported by statistical model calculations based on the transition-state model of fission. The elastic scattering data present enhanced back-angle yields which can be understood in terms of a compound elastic process. These results help to further establish the reaction systematics in this mass region.

We have studied fission product yields using 19.8 MeV proton induced fission of a thin ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ target and the on-line mass separator IGISOL. The nonselectivity of the separation method used with respect to Z has allowed accurate determination of the yields of symmetric fission for the first time. The cumulative yields for the elements from Z=40 (Zr) up to Z=47 (Ag) have been determined from the beta- and gamma-radioactivity measurements. The independent fission product yield distributions for elements Tc, Ru, and Rh are obtained from the experimental data. An improved theoretical model for calculating mass and independent yields is described and applied. It is found that the charge splitting for the primary fragments differs from that obtained with the unchanged charge division model at moderate excitation energies of compound nuclei. A comparison of the calculated and experimental fission product yields shows that the model presented can be applied for predictions of cross sections for very neutron-rich nuclei in the light particle induced fission.

We have measured cross sections and analyzing powers for ${\mathrm{\pi }}^{+}$ and ${\mathrm{\pi }}^{\mathrm{-}}$ elastic scattering from a polarized ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ target at ${\mathit{T}}_{\mathrm{\pi }}$=100 MeV. Measurements have been made over an angular range of 60° to 110° which extends over the region of the cross section minimum where spin effects in π-nucleus scattering are predicted to be largest. This is evident from the large value of ${\mathit{A}}_{\mathit{y}}$ observed in ${\mathrm{\pi }}^{+}$ scattering from ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ near ${\mathrm{\theta }}_{\mathrm{lab}}$=80°. The ${\mathit{A}}_{\mathit{y}}$ data for both ${\mathrm{\pi }}^{+}$ and ${\mathrm{\pi }}^{\mathrm{-}}$ scattering are qualitatively reproduced by a schematic PWIA model; however, agreement with the data is significantly improved when a full nonlocal DWIA reaction model employing realistic three-body wave functions is used. The asymmetry in ${\mathrm{\pi }}^{\mathrm{-}}$${\mathrm{-}}^3$He scattering resembles the asymmetry for ${\mathrm{\pi }}^{\mathrm{-}}$ scattering from a free neutron near the cross section minimum and is about half that for ${\mathrm{\pi }}^{+}$ scattering.