The neutron distributions of Cs, Ba, Yb, and Pb isotopes are described in the framework of relativistic mean-field theory. The self-consistent ground-state proton and neutron density distributions are calculated with the relativistic Hartree-Bogoliubov model. The binding energies, the proton and neutron radii, and the quadrupole deformations are compared with available experimental data, as well as with recent theoretical studies of the nuclear structure corrections to the weak charge in atomic parity nonconservation experiments.

We discuss the relativistic nuclear equation of state (EOS) using a relativistic transport model in heavy-ion collisions. From the baryon flow for Au + Au systems at SIS to AGS energies and above we find that the strength of the vector potential has to be reduced moderately at high density or at high relative momenta to describe the flow data at (1–10)A GeV. We use the same dynamical model to calculate the nuclear EOS and then employ this to calculate the gross structure of a neutron star considering the core to be composed of neutrons with an admixture of protons, electrons, muons, sigmas, and lambdas at zero temperature. We then discuss these gross properties of neutron stars such as maximum mass and radius in contrast to the observational values.

Experiments on neutrinoless double beta $\left(0\mathrm{}\nu \beta \beta \right)$ decay to excited $0^{+}$ states are a promising tool to study neutrino and weak-interaction properties by reducing the background of the measured spectra by the associated gamma-coincidence signals. Drawbacks are the lower Q value of the decays and possibly the smallness of the involved nuclear matrix elements as compared to the decays to the final ground state. In this Rapid Communication it is suggested that the first excited $0^{+}$ state in ${}^{96}\mathrm{Mo}$ can be described as a monopole-vibrational state and $0\nu \beta \beta$ decay of ${}^{96}\mathrm{Zr}$ to this particular state could yield to $8\times {10}^{-2}$ eV limit for the Majorana-neutrino mass in modern underground experiments using huge active-mass detectors.

Excited structures in the $Z=80,{\hspace{0.5em}}^{178}\mathrm{Hg}\hspace{0.5em}\mathrm{}(N=98\mathrm{}),$ and ${}^{180}\mathrm{Hg}\hspace{0.5em}\mathrm{}(N=100\mathrm{})\mathrm{}$ isotopes have been investigated with the Gammasphere spectrometer in conjunction with the recoil-decay tagging technique. The present data extend the previously known ground-state bands to higher spin and excitation energy. Negative parity bands with a complex decay towards the low spin states arising from both the prolate-deformed and the nearly spherical coexisting minima have been observed for the first time in both nuclei. It is shown that these sequences have characteristics in common with negative-parity bands in the heavier even-even Hg isotopes as well as in the Os and Pt isotones. These structures are interpreted as being associated at low spin with an octupole vibration which is crossed at moderate frequency by a shape driving, two-quasiproton excitation.

Using a comparative delayed coincidence technique the lifetime of the $6_1^{+}$ level in ${}^{144}\mathrm{Nd}$ has been measured as $\tau =30\mathrm{}\pm 3$ ps, leading to a ${B(E2;6\mathrm{}}_1^{+}\to 4_1^{+})$ value of $25\pm 3$ W.u. This value is almost a factor of 3 less than that expected for a purely collective three-phonon state, but is in agreement with particle-core coupling calculations that predict significant noncollective $L=4\mathrm{}$ and $L=6\mathrm{}$ components in the $4^{+}$ and $6^{+}$ yrast state wave functions.

The relativistic Hartree-BCS theory is applied to study the temperature dependence of nuclear shape and pairing gap for ${}^{166}\mathrm{Er}$ and ${}^{170}\mathrm{Er}.$ For both the nuclei, we find that as temperature increases the pairing gap vanishes leading to phase transition from superfluid to normal phase as is observed in nonrelativistic calculation. The deformation evolves from prolate shapes to spherical shapes at $T\sim 2.7$ MeV. Comparison of our results for heat capacity with the ones obtained in the nonrelativistic mean field framework indicates that in the relativistic mean field theory the shape transition occurs at a temperature about 0.9 MeV higher and is relatively weaker. The effect of thermal shape fluctuations on the temperature dependence of deformation is also studied. Relevant results for the level density parameter are further presented.

The multipole amplitudes for the $N-\Delta \mathrm{}\left(1232\right)\mathrm{}$ electromagnetic transition are computed in the framework of the linear $\sigma$ model and the chiral chromodielectric model for small and moderate photon virtualities. The models include quark and meson degrees of freedom and the nucleon and the $\Delta$ are clusters of three valence hedgehog quarks surrounded by meson clouds described by coherent states. Angular momentum and isospin projections are performed to endow model states representing the nucleon and the $\Delta$ with proper quantum numbers. Recoil corrections involved in the process ${\gamma }_{\mathrm{v}}\overrightarrow{N}\Delta$ are taken into account by performing linear momentum projection of the initial and final baryon states. The ratios $E2/M1\mathrm{}$ and $C2/M1\mathrm{}$ are in good agreement with the data in the two models, but the magnetic amplitude is better reproduced in the linear $\sigma$ model. The ratios show little dependence with the model parameters. Both in the linear $\sigma$ model and in the chromodielectric model the charged pions are responsible for the nonvanishing quadrupole-electric and -Coulomb amplitudes. The recoil corrections enhance the results obtained for the amplitudes without linear momentum projection, improving the comparison with experimental data. The dependence of the theoretical amplitudes with the choice of the reference frame is also studied.

Knowledge of the astrophysical ${}^{18}\mathrm{F}(p,\alpha {)}^{15}\mathrm{O}$ rate is important for understanding gamma-ray emission from novae and heavy-element production in x-ray bursts. A state with $E_x\simeq 7.08\hspace{0.5em}\mathrm{MeV}$ in ${}^{19}\mathrm{Ne}$ provides an s-wave resonance and, depending on its properties, could dominate the ${}^{18}\mathrm{F}(p,\alpha {)}^{15}\mathrm{O}$ rate. By measuring a kinematically complete ${}^1\mathrm{H}{(}^{18}\mathrm{F}{,p)}^{18}\mathrm{F}$ excitation function with a radioactive ${}^{18}\mathrm{F}$ beam at the ORNL Holifield Radioactive Ion Beam Facility, we find that the ${}^{19}\mathrm{Ne}$ state lies at a center-of-mass energy of $665.3\pm 1.7\hspace{0.5em}\mathrm{keV}$ ${(E}_x=7077\mathrm{}\pm 2\hspace{0.5em}\mathrm{keV}),$ has a total width of $38.5\pm 3.4\hspace{0.5em}\mathrm{keV},$ and a proton partial-width of $15.8\pm 1.6\hspace{0.5em}\mathrm{keV}.$

Levels in the odd-odd nucleus ${}^{100}\mathrm{Nb}$ situated at the edge of a region of especially fast shape transitions have been calculated in the framework of the interacting boson fermion fermion model. Levels observed in decay studies can be interpreted in a spherical basis. Low-lying $I^{\pi }{=8\mathrm{}}^{+}$ and ${10}^{-}$ states are predicted. Their relationship with the unplaced levels populated with a $12\hspace{0.5em}\mu \mathrm{s}$ delay after fission is discussed.

The recursive techniques developed by Mekjian and collaborators for exact calculations of canonical partition functions of fragmenting systems are extended to allow the determination of fragment multiplicity distributions. The fragment multiplicity distribution is shown to become strongly super-Poissonian at the critical temperature. This behavior is shown to be highly sensitive to Coulomb effects and to whether energy is strictly conserved (the microcanonical ensemble). Additionally, a method is presented for generating events from the partition functions, which also permits the inclusion of hard-sphere interactions between fragments.

The charged particle decay of continuum states excited by the single proton stripping reaction ${(}^7{\mathrm{L}\mathrm{i},\mathrm{}}^6\mathrm{He})$ at a bombarding energy of 50 MeV/nucleon on targets of ${}^{40}\mathrm{Ca}$ and ${}^{90}\mathrm{Zr}$ was measured and compared with theoretical predictions. The results suggest that most of the strength in the continuum arises from decay of unbound states in the intermediate nucleus rather than from breakup of the ${}^7\mathrm{Li}$ projectile. There is substantial direct decay to the low-lying states in the final nucleus for both targets.

Differential spectra of coherent photon bremsstrahlung in relativistic heavy-ion collisions are calculated within various schematic models of the projectile-target stopping. Two versions of the degradation length model, based on a phenomenological deceleration law, are considered. The simple shock wave model is studied analytically. The predictions of these models agree in the soft photon limit, where the spectrum is determined only by the final velocity distribution of charged particles. The results of these models in the case of central $\mathrm{Au}+\mathrm{Au}$ collisions at the AGS bombarding energy are compared with the predictions of the microscopic transport model UrQMD. The latter model is also used to calculate photon spectra at SIS, SPS, and RHIC energies. It is shown that at the AGS energy the coherent photon bremsstrahlung exceeds the photon yield from ${\pi }^0$ decays at c.m. photon energies $\omega \lesssim 50\hspace{0.5em}\mathrm{MeV}.$

We evaluate the cross sections for the dissociation of $J/\psi$ and ${\psi }^{\prime }$ by $\pi$ and $\rho$ at low collision energies, using the quark-interchange model of Barnes and Swanson. The dissociation cross section for $J/\psi$ by $\pi$ is found to be relatively small with a maximum of about 1 mb and a kinetic energy threshold of 0.65 GeV. The pion-induced ${\psi }^{\prime }$ dissociation cross section is found to be much larger, with a maximum of about 5 mb and a lower threshold. Dissociation cross sections for $J/\psi$ and ${\psi }^{\prime }$ by $\rho$ mesons are also evaluated and are found to be large near threshold.

Using triple-coincidence events of prompt fission gamma rays from 1995 Gammasphere data on spontaneous fission of ${}^{252}\mathrm{Cf},$ we made a careful analysis of the yield matrix of coincident pairs of barium $\mathrm{}(Z=56\mathrm{})\mathrm{}$ and molybdenum $\mathrm{}(Z=42\mathrm{})\mathrm{}$ fission fragments. Branching from gamma bands $\mathrm{}(K=2\mathrm{})\mathrm{}$ and octupole bands $\mathrm{}(K=0\mathrm{})\mathrm{}$ are presented for even-even partners, where observable. From this reanalysis the previously proposed “extra-hot-fission mode” (up to ten neutrons evaporated) as determined by twofold coincidences of 1993 Gammasphere data is much weaker, but not excluded. This finding is in agreement with a recently published similar study from the Legnaro gamma-detector array.

We have measured the ${}^{147}\mathrm{Sm}(n,\alpha )$ cross section from 3 eV to 500 keV. These data were used to test nuclear statistical models which must be relied on to calculate the rates for as yet unmeasurable reactions occurring in explosive nucleosynthesis scenarios. It was found that our data are in reasonably good agreement with the reaction rate predicted by an older model but that the rates predicted by two very recent models are roughly a factor of 3 different from the data (in opposite directions). A detailed analysis indicates the strong dependence on the employed optical $\alpha$ potentials. These results, together with counting rate estimates for future experiments indicate that $(n,\alpha )$ measurements will be useful for improving reaction rate predictions across the global range of masses needed for explosive nucleosynthesis calculations.

The positive-parity bands observed in the even ${}^{72-84}\mathrm{Kr}$ isotopes have been studied in the framework of the IBA-2 model. The analysis includes states of spin up to the maximum allowed by the finite boson number. The symmetry character of these bands in the proton and neutron degrees of freedom has been investigated. Excitation energies, $B\left(E2\mathrm{}\right)\mathrm{}’s$ of intraband transitions and $B\left(E2\mathrm{}\right)\mathrm{}’s,$ $B\left(M1\mathrm{}\right)\mathrm{}’s,$ $E2/M1\mathrm{}$ mixing ratios of interband transitions have been considered. Three bands of different structure can be accounted for in the framework of the model: the ground-state band, of predominant full-symmetry character; the band built on the $2_2^{+}$ state, which is composed by states which show different symmetry character along the isotopic chain; and the band built on the $3_1^{+}$ state, of predominant mixed-symmetry character.

Neutron-rich ${}^{147,149,151}\mathrm{Pr}$ nuclei, produced in the spontaneous fission of ${}^{252}\mathrm{Cf},$ were studied using the Gammasphere array. Possible parity doublets in ${}^{147}\mathrm{Pr}$ with $N=88\mathrm{}$ and $\pi h_{11/2}$ bands in ${}^{149,151}\mathrm{Pr}$ are proposed. These new data on the level structures of odd Pr isotopes suggest that octupole correlations may also be present in the neutron-rich ${}_{59}^{147}{\mathrm{Pr}}_{88}$ nucleus such as those observed in ${}_{58}^{146}{\mathrm{Ce}}_{88},$ and also that the $h_{11/2}$ bands in the ${}^{149,151}\mathrm{Pr}$ track in energy the yrast bands in ${}^{148,150}\mathrm{Ce}.$ The backbending related to the breaking of the neutron $i_{13/2}$ pair is observed at $ħ\omega \approx 0.27\hspace{0.5em}\left(\mathrm{MeV}\right)$ for the proton $h_{11/2}$ band of ${}^{149}\mathrm{Pr}.$

Longitudinal momentum distributions and total diffraction and stripping cross sections for production of ${}^{10}\mathrm{Be}$ and ${}^{14}\mathrm{C}$ fragments in ground and excited states, by removal of a valence neutron or a core neutron, are studied in the eikonal approximation for the ${}^9\mathrm{Be}{(}^{11}\mathrm{Be},$ ${}^{10}\mathrm{Be}+\gamma )$ and ${}^9\mathrm{Be}{(}^{15}\mathrm{C},$ ${}^{14}\mathrm{C}+\gamma )$ reactions. A consistent description of recent exclusive data for individual ${}^{10}\mathrm{Be}$ states is obtained, giving support to the procedure. Predictions for ${}^{14}\mathrm{C}$ are in agreement with available inclusive and limited inclusive data, and argue for halo model for ${}^{15}\mathrm{C}.$ The sensitivity of the results to the structural assumptions and interaction potentials is discussed.

It was recently argued that in heavy ion collisions the parity could be broken. This paper addresses the question of the possibility of the experimental detection of the effect. We discuss how parity violating effects would modify the final particle distributions and how one could construct variables sensitive to the effect, and which measurement would be the (most) conclusive. Discussing different observables we also discuss the question of whether the “signals” can be faked by “conventional” effects (such as anisotropic flow, etc.) and make estimates of the signals.

The strength function and partial widths for the direct nucleon decay of the isoscalar giant monopole and dipole resonances are analyzed within an extended continuum-random-phase-approximation approach. Calculations are performed for several medium and heavy mass nuclei with the use of a phenomenological nuclear mean field, the Landau-Migdal particle-hole interaction, and some partial self-consistency conditions. Calculation results are compared with available experimental data.