The role of the relativistic amplitudes for a number of O(k) processes usually neglected in potential model calculations of NN bremsstrahlung is investigated. In particular, we consider the Δ excitation pole contributions related to the one-pion and one-rho exchange and in addition include the exchange contributions induced by the radiative ω,p→πγ decays. The contributions are calculated from relativistic Born amplitudes fitted to Δ production and absorption data in the energy range up to 1 GeV and then used to supplement potential model and soft photon calculations for nucleon-nucleon bremsstrahlung. The effects on NNγ observables, although moderate in general, are found to be important in some kinematic domains.

Excitation of the 17.4 s ${}_{}{}^{77}{}_{}{}^{}\mathrm{Se}_{}^{\mathit{m}}{}_{}{}^{}$, 4.9 s ${}_{}{}^{79}{}_{}{}^{}\mathrm{Br}_{}^{\mathit{m}}{}_{}{}^{}$, and 4.9 s ${}_{}{}^{191}{}_{}{}^{}\mathrm{Ir}_{}^{\mathit{m}}{}_{}{}^{}$ isomers by γ rays of a strong ${}_{}{}^{137}{}_{}{}^{}\mathrm{Cs}$ source was observed for the first time. Using a 67 TBq (1800 Ci) source for irradiation, isomeric activities were measured by means of γ spectrometry. Identifying principal activation levels, photoexcitation cross sections were determined, allowing level lifetimes to be deduced.

The ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$${(}^{16}$O,4α${)}^{12}$C reaction has been studied at a beam energy of 99 MeV. The data indicate the existence of sequential decays in the form ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}_{}^{\mathrm{*}}{}_{}{}^{}$→4α in the exit channel. The excitation energy of the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ nucleus and the nature of the partition process leading to the 4α final state, has been reconstructed from the kinematics of the α particles. States have been observed at excitation energies of 17.1, 17.5, 18.0, 18.7, 19.3, and 21.4 MeV which decay into ${}_{}{}^8{}_{}{}^{}\mathrm{Be}$${+}^8$Be, ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(7.65 MeV, $0_2^{+}$)+α and ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(9.64 MeV, $3^{\mathrm{-}}$)+α. Relative partial decay widths for these three channels have been measured. Angular correlation measurements have been used to deduce the spins of several of the observed states, and indicate spins in the range 2 to 6ħ.

Multiplicity distributions of neutrons and energy spectra of light charged particles have been measured in coincidence with evaporation residues from the ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$${+}^{118,124}$Sn fusion reactions at ${\mathit{E}}_{\mathrm{lab}}$=130–180 MeV. The experimental data are found to be in agreement with the results of statistical-model calculations, provided a=A/12 ${\mathrm{MeV}}^{\mathrm{-}1}$ is assumed for the effective level-density parameter for all nuclides in the decay path. Simulation calculations have further shown that such a low value of the level-density parameter cannot be explained as a result of a possible population of superdeformed bands, unaccounted for by the statistical-decay code.

High-spin states in the ${}_{}{}^{133}{}_{}{}^{}\mathrm{Ba}$ nucleus have been populated using the ${}_{}{}^{124}{}_{}{}^{}\mathrm{Sn}$${(}^{13}$C,4n) reaction. Excited states were observed up to I=45/2 and several bands were constructed. Most of the observed bands are characterized by intense dipole transitions. At low spin, bands built on mixed ν${\mathit{s}}_{1/2}$ and ν${\mathit{d}}_{3/2}$ configurations and on the ν${\mathit{h}}_{11/2}$ configuration were observed. The latter band is associated with a large signature splitting of about 300 keV. According to total Routhian surface calculations, in this band the nucleus has a triaxial shape with γ≊-80°. At higher spin, bands built on three- and five-quasiparticle configurations were identified. These bands may possess a weakly deformed shape with either γ>0° or γ<-60°, depending on the number of ${\mathit{h}}_{11/2}$ protons and neutrons involved in the configuration.

The experimental level structure of ${}_{}{}^{223}{}_{}{}^{}\mathrm{Fr}$ has been studied using the 1.4% alpha decay of 21.8 yr ${}_{}{}^{227}{}_{}{}^{}\mathrm{Ac}$ and subsequent gamma rays to extend the level scheme recently observed following the ${\mathrm{\beta }}^{\mathrm{-}}$ decay of ${}_{}{}^{223}{}_{}{}^{}\mathrm{Rn}$. The level structure of ${}_{}{}^{223}{}_{}{}^{}\mathrm{Fr}$ was also studied theoretically by using the quasiparticle model of Soloviev with octupole degrees of freedom. Both experimentally and theoretically there is strong evidence that ${}_{}{}^{223}{}_{}{}^{}\mathrm{Fr}$ is reflection asymmetric. The theoretical study of microscopic structure of several of the positive-parity bands also indicates the presence of important Nilsson configurations arising from the shell below. The comparison of the level structures of ${}_{}{}^{223}{}_{}{}^{}\mathrm{Fr}$, ${}_{}{}^{221}{}_{}{}^{}\mathrm{Fr}$, and ${}_{}{}^{219}{}_{}{}^{}\mathrm{Fr}$ tends to elaborate the mechanism by which the octupole-modified Nilsson orbitals collapse into the more degenerate shell model states as the mass number decreases.

A new in-beam study in ${}_{}{}^{183}{}_{}{}^{}\mathrm{Hg}$ levels has been carried out by using the ${}_{}{}^{155}{}_{}{}^{}\mathrm{Gd}$${(}^{32}$S,4n) reaction at a beam energy of 160 MeV. A new pair of signature-partner bands, with large signature splitting, has been established in ${}_{}{}^{183}{}_{}{}^{}\mathrm{Hg}$. The band head of these signature-partner bands is assigned to be the ground state of ${}_{}{}^{183}{}_{}{}^{}\mathrm{Hg}$ with a configuration of 1/$2^{\mathrm{-}}$[521]. The measured ratios of directional correlations (DCO ratios) revealed decay patterns for the proposed 9/$2^{+}$[624] bands in ${}_{}{}^{183}{}_{}{}^{}\mathrm{Hg}$ different from those of ${}_{}{}^{185}{}_{}{}^{}\mathrm{Hg}$.

The isoscalar spin strength in ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ has been studied in the inelastic scattering of polarized 400 MeV deuterons. The measurements were carried out over an angular range from 3° to 7° and an excitation energy range from 11 to 58 MeV (momentum transfer range from 0.34 to 0.92 ${\mathrm{fm}}^{\mathrm{-}1}$). Previously unknown spin excitations were found in the 20-MeV region and over a broad range in the continuum with a cluster of strength around 30 MeV. The results are compared with spin-flip probability measurements in proton scattering. Below 35 MeV of excitation energy, the isoscalar relative spin response is strongly enhanced above the noninteracting Fermi gas value of 0.5. Above 35 MeV of excitation the spin response drops below 0.5.

The α and β decays of ${}_{}{}^{169\mathrm{-}173}{}_{}{}^{}\mathrm{Os}$ were studied using ${}_{}{}^{114}{}_{}{}^{}\mathrm{Cd}$${(}^{58}$Ni,xn) and ${}_{}{}^{140}{}_{}{}^{}\mathrm{Ce}$${(}^{36}$Ar,xn) reactions. For ${}_{}{}^{169,171}{}_{}{}^{}\mathrm{Os}$ new α rays and α-coincident γ rays were observed; for ${}_{}{}^{170\mathrm{-}173}{}_{}{}^{}\mathrm{Os}$ β-delayed γ transitions could be identified for the first time. Evidence for isomeric states in ${}_{}{}^{171,173}{}_{}{}^{}\mathrm{Re}$ was found. The nuclear structure in the daughter isotopes is interpreted in terms of single-particle states in the frame of the Nilsson model.

High-spin states have been studied in the very neutron deficient N=74 nucleus, ${}_{}{}^{136}{}_{}{}^{}\mathrm{Sm}$ with the reaction ${}_{}{}^{107}{}_{}{}^{}\mathrm{Ag}$${(}^{32}$S,p2n${)}^{136}$Sm. Using time-correlated charged-particle–γ–γ spectroscopy, a rotational cascade built upon the ${\mathit{t}}_{1/2}$=15 μs, ${\mathit{K}}^{\mathrm{\pi }}$=$8^{\mathrm{-}}$ isomer has been identified. Although equivalent isomers are known in other N=74 isotones, this represents the only case where the associated band has been observed. The in-band decay properties of this structure are consistent with a 7/$2^{+}$[404]⊗9/$2^{\mathrm{-}}$[514] two quasineutron assignment. A second high-K band, probably of a four-quasiparticle nature, is observed to feed into the ${\mathit{K}}^{\mathrm{\pi }}$=$8^{\mathrm{-}}$ band.

We have studied the equations of state of nuclear matter using the nonlinear σ-ω model. At the normal density, there is a strong correlation among the effective nucleon mass ${\mathit{M}}_0^{\mathrm{*}}$, the incompressibility, K and the third derivative K’ of binding energy. The results are compared with the empirical analysis of the giant isoscalar monopole resonances data. It is difficult to fit the data when K≲200 MeV, using the model. It is also found that K=300±50 MeV is favorable to account for the volume-symmetry properties of nuclear matter.

Cluster-decays of the neutron-deficient ${}_{}{}^{108\mathrm{-}116}{}_{}{}^{}\mathrm{Xe}$, ${}_{}{}^{112\mathrm{-}120}{}_{}{}^{}\mathrm{Ba}$, ${}_{}{}^{116\mathrm{-}124}{}_{}{}^{}\mathrm{Ce}$, ${}_{}{}^{120\mathrm{-}124}{}_{}{}^{}\mathrm{Nd}$, ${}_{}{}^{124\mathrm{-}128}{}_{}{}^{}\mathrm{Sm}$, and ${}_{}{}^{128\mathrm{-}132}{}_{}{}^{}\mathrm{Gd}$ parents are studied within the preformed cluster model of Malik and Gupta. The calculated preformation probabilities (${\mathit{P}}_0$) and decay half-lives show that the α-nuclei (${\mathit{A}}_2$=4n, ${\mathit{Z}}_2$=${\mathit{N}}_2$) clusters, like ${}_{}{}^8{}_{}{}^{}\mathrm{Be}$, ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$, ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$, and ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$, emitted form N=Z parents are the most probable cases for measurements. Many of these clusters are shown to be within the upper limit of present experimental methods. This stresses the importance of ${}_{50}{}^{100}{}_{}{}^{}$ Sn-daughter in these decays. The fact that ${\mathit{A}}_2$=4n cluster-decays are more probable than ${\mathit{A}}_2$=4n+2 clusters demonstrates that Sn radioactivity is associated with ${\mathit{A}}_2$=4n, ${\mathit{Z}}_2$=${\mathit{N}}_2$ (α-nuclei) clusters. Structure effects of the nuclear (proximity) potential and binding energies (the shell effects) in GN plots are in variation of ${\mathit{P}}_0$ with the parent mass A are also pointed out.

The evaluation of partition functions in the grand-canonical and canonical ensembles and the accuracy of the ensuing saddle-point approximations for the many-body energy level density are investigated. A simple method for obtaining the canonical partition function and average energy using the saddle-point approximation is also examined. Results are shown for the nucleus ${}_{}{}^{164}{}_{}{}^{}\mathrm{Er}$ within an independent-particle model, where a comparison with the exact level density of the model is made.

We examine here how the nuclear Born-Oppenheimer (NBO) method describes the collective dynamics of nuclei undergoing small-amplitude oscillations around the equilibrium state. After specifying the NBO trial wave function, and assuming that the intrinsic state is not very different from the Hartree-Fock (HF) ground state, we show that the NBO method yields the random phase approximation (RPA) equations. We then derive an expression for the ground state energy. This expression, which contains zero-point energy correction terms, is smaller than the static HF energy. Next, we derive the correlated ground state energy and then show that it is identical with the corresponding expressions obtained from the generator-coordinate method, from the properly quantized adiabatic time-dependent Hartree-Fock approach, and from the RPA.

Hypernuclear spectra are calculated by using the scalar derivative-coupling model of Zimanyi and Moszkowski. Although the fit is not unique, as in similar models, the experimental data are reproduced with accuracy. We discuss also how much information is contained in the spectroscopic data concerning the properties of the Λ in nuclear matter. In particular, we discuss the saturation density and the minimum of the chemical potential of the Λ particle.

Symmetric and asymmetric nuclear matter is studied in the framework of the relativistic Brueckner-Hartree-Fock and in the relativistic version of the so-called ${\mathrm{\Lambda }}^{00}$ approximation. The equations are solved self-consistently in the full Dirac space, so avoiding the ambiguities in the choice of the effective scattering amplitude in matter. The calculations were performed for some modern meson-exchange potentials constructed by Brockmann and Machleidt. In some cases we used also the Groningen potentials. First, we examine the outcome for symmetric matter with respect to other calculations, which restrict themselves to positive-energy states only. The main part is devoted to the properties of asymmetric matter. In this case we obtain additionally to the good agreement with the parameters of symmetric matter, also a quite satisfactory agreement with the semiempirical macroscopic coefficients of asymmetric matter. Furthermore, we tested the assumption of a quadratic dependence of the asymmetry energy for a large range of asymmetries. Included is also the dependence of nucleon self-energies on density and neutron excess. For the purpose of comparison we discuss further the similarities and differences with relativistic Hartree and Hartree-Fock calculations and nonrelativistic Skyrme calculations.

The spectral function for finite nuclei is computed within the framework of the local-density approximation, starting from nuclear matter spectral functions obtained with a realistic nucleon-nucleon interaction. The spectral function is decomposed into a single-particle part and a ‘‘correlated’’ part; the latter is treated in the local-density approximation. As an application momentum distributions, quasiparticle strengths and overlap functions for valence hole states, and the light-cone momentum distribution in finite nuclei are computed.

In a realistic calculation the L-S coupling scheme is restored not only for the parity doublet levels but also for some other levels in the superdeformed limit, because of the strongly deformed quadrupole interaction. This real-spin mechanism can take into account the unique-parity level, in contrast to the pseudo-spin mechanism. The contribution from the unique-parity level to the M1 transition becomes nonnegligible when the nucleus is superdeformed.

The anomalous bandcrossing observed in the [541] ↓ bands of odd-Z nuclei from the rare-earth region was investigated in the framework of the particle-rotor model. The participation of the decoupling term in the K=1/2 band will give rise to a significant shift of the bandcrossing frequency, with an amplitude comparable to the observed values.

We discuss the ability of the generator coordinate method (GCM) to select collective states in microscopic calculations. The model studied is a single-j shell with a Hamiltonian containing the quadrupole-quadrupole interaction. Quadrupole-collective excitations are constructed by means of the quadrupole single-particle operator. Lowest collective bands for j=31/2 and particle numbers N=4, 6, 8, 10, 12, and 14 are found. For lower values of j, exact solutions are obtained and compared with the GCM results.