In the last several years new experimental data have become available on alpha-decay chains starting in the predicted deformed superheavy region near ${}^{272}110.$ This has promoted new interest in nuclear mass formulas and how well they extrapolate to regions far beyond where experimental masses were previously known. We here focus on two such mass models, namely the fermion dynamical symmetry model and the finite-range droplet model. We have chosen these models since they both reproduce previously known actinide masses with good accuracy, but rapidly diverge from each other in the region of the recently observed new elements. Furthermore, the two models have been the subject of animated discussions concerning which one gives the most reliable predictions of nuclear masses in the superheavy region and in the terminating region of the r process. The new data support the predictions of the finite-range droplet model. We discuss the fermion dynamical symmetry model and its application [Han et al., Phys. Rev. C 45, 1127 (1992)] to the calculation of trans-Pb nuclear masses. As will be shown, the model contains unphysical features and has many more free constants than claimed. The values obtained for the constants and the model agreement with data in the region of adjustment are therefore of no particular significance and severe divergences occur for recently discovered nuclei outside the region of adjustment.

We present realistic models of pion-exchange three-nucleon interactions obtained by fitting the energies of all the 17 bound or narrow states of $3<~A<~8$ nucleons, calculated with less than 2% error using the Green’s function Monte Carlo method. The models contain two-pion-exchange terms due to $\pi N$ scattering in S and P waves, three-pion-exchange terms due to ring diagrams with one $\Delta$ in the intermediate states, and a phenomenological repulsive term to take into account relativistic effects, the suppression of the two-pion-exchange two-nucleon interaction by the third nucleon, and other effects. The models have five parameters, consisting of the strength of the four interactions and the short-range cutoff. The 17 fitted energies are insufficient to determine all of them uniquely. We consider five models, each having three adjustable parameters and assumed values for the other two. They reproduce the observed energies with an rms error $<1\%$ when used together with the Argonne $v_{18}$ two-nucleon interaction. In one of the models the $\pi N$ S-wave scattering interaction is set to zero; in all others it is assumed to have the strength suggested by chiral effective-field theory. One of the models also assumes that the $\pi N$ P-wave scattering interaction has the strength suggested by effective-field theories, and the cutoff is adjusted to fit the data. In all other models the cutoff is taken to be the same as in the $v_{18}$ interaction. The effect of relativistic boost correction to the two-nucleon interaction on the strength of the repulsive three-nucleon interaction is estimated. Many calculated properties of $A<~8$ nuclei, including radii, magnetic dipole, and electric quadrupole moments, isobaric analog energy differences, etc., are tabulated. Results obtained with only Argonne $v_8^{\prime }$ and $v_{18}$ interactions are also reported. In addition, we present results for seven- and eight-body neutron drops in external potential wells.

A model for energy, pressure, and flow velocity distributions at the beginning of ultrarelativistic heavy ion collisions is presented, which can be used as an initial condition for hydrodynamic calculations. Our model takes into account baryon recoil for both target and projectile, arising from the acceleration of partons in an effective field $F^{\mu \nu }$ produced in the collision. The typical field strength (string tension) for RHIC energies is about 5–12 GeV/fm, which allows us to talk about “string ropes.” The results show that a quark-gluon plasma forms a tilted disk, such that the direction of the largest pressure gradient stays in the reaction plane, but deviates from both the beam and the usual transverse flow directions. Such initial conditions may lead to the creation of “antiflow” or “third flow component” [L. P. Csernai and D. Röhrich, Phys. Rev. Lett. B 458, 454 (1999)].

The thermal evolution of the shell-correction energy is investigated for deformed nuclei using Strutinsky prescription in a self-consistent relativistic mean-field framework. For temperature independent single-particle states corresponding to either spherical or deformed nuclear shapes, the shell-correction energy ${\Delta }_{\mathrm{sc}}$ steadily washes out with temperature. However, for states pertaining to the self-consistent thermally evolving shapes of deformed nuclei, the dual role played by the single-particle occupancies in diluting the fluctuation effects from the single-particle spectra and in driving the system towards a smaller deformation is crucial in determining ${\Delta }_{\mathrm{sc}}$ at moderate temperatures. In rare-earth nuclei, it is found that ${\Delta }_{\mathrm{sc}}$ builds up strongly around the shape transition temperature; for lighter deformed nuclei like ${}^{64}\mathrm{Zn}$ and ${}^{66}\mathrm{Zn},$ this is relatively less prominent.

Collective $E2\mathrm{}$ strengths were measured to probe the two-phonon γ-vibrational character of $I_K^{\pi }{=4\mathrm{}}_4^{+}$ states for ${}^{188,190}\mathrm{Os}.$ Lifetimes for states with spin up to $8^{+}$ of the ground-state band, $6^{+}$ of the γ band, and the $4^{+}$ state of the $K^{\pi }{=4\mathrm{}}^{+}$ band were measured by the recoil-distance method following Coulomb excitation by a ${}^{58}\mathrm{Ni}$ projectile at $E_{\mathrm{lab}}=275\mathrm{}\hspace{0.5em}\mathrm{MeV}.$ These lifetime data are compared with the electromagnetic matrix elements measured by previous Coulomb excitation experiments. The good agreement between these independent measurements supports the conclusion, made by the Coulomb excitation work, that the electromagnetic properties of these osmium nuclei are consistent with the description of γ-soft collective models. In addition, it supports the evidence that the two-phonon γ-vibration configuration is the dominant component for the lowest-lying $I_K^{\pi }{=4\mathrm{}}_4^{+}$ states in osmium nuclei.

In a recent paper Hui et al. fit their evaporation residue data with CASCADE calculations equally well with and without nuclear viscosity by scaling the fission barrier with different scaling factors. I find that the need for scaling the fission barrier is an artifact of the level density calculation incorporated into the original CASCADE code. Contrary to the findings of Hui et al. the evaporation residue cross section is a very sensitive measure of the nuclear viscosity, if the calculations are done without scaling the fission barrier using a more recent level density method.

We agree with the preceding Comment that the evaporation residue cross-section measurement is indeed a sensitive tool to study nuclear viscosity. The CASCADE calculations with the improved level-density description used by Diószegi reproduce our evaporation residue measurement without nuclear viscosity. However, our CASCADE calculations were not used to reproduce the absolute magnitude of the evaporation residue cross section but rather the shape of the spin distribution. The calculations show that the spin distribution can be fitted to the standard calculation without dissipation in agreement with the Comment by Diószegi. We conclude that the need to include nuclear viscosity effects in previous measurements must be due to strong viscosity outside of the saddle point.

The drip line of F isotopes is discussed from the viewpoint of a unified description of exotic nuclei with $N\sim 20.$ The structure of those nuclei is described by means of large-scale shell model calculations, most of which are Monte Carlo shell model. It is shown that, due to the narrowing of the $N=20\mathrm{}$ shell gap towards smaller Z, the mixing among normal, intruder, and higher intruder configurations can be enhanced significantly, and can produce crucial effects, including the F drip line located extremely far from the O drip line. The feasibility of Monte Carlo shell model is demonstrated for systems with an odd number of fermions.

In order to study collective instabilities in symmetric nuclear matter, a simple phenomenological nucleon-nucleon finite-range potential with three adjustable parameters is proposed. The three parameters are the attractive strength, the attractive range, and the (zero range) repulsive strength. The potential reproduces the binding energy, equilibrium density, compressibility modulus, and the effective mass of nuclear matter, as well as the binding energies of ${}^4\mathrm{He},$ ${}^{16}\mathrm{O},$ and ${}^{40}\mathrm{Ca}.$ The latter conditions are crucial for preventing spurious “quasicrystallization” effects in nuclear matter. With this potential and a $\mathrm{}(2+1)\mathrm{}$-D deformed oscillator basis, variational Hartree-Fock calculations extending over the configuration space of the lowest 55 orbitals were performed for spin-zero, isospin-zero light nuclei up to $A=80.\mathrm{}$ Large ground-state deformations and exotic nuclear shapes were found for many nuclei. Implications for their rotational spectra are discussed.

Symmetric nuclear matter is found to have a spontaneously broken translational symmetry. This collective instability creates a one-dimensional nucleon density wave of periodicity 15–27 fm, with a peak-to-trough density ratio ∼6. As a result, the binding energy of the system increases by 0.5–1.5 MeV per nucleon relative to that for uniform nuclear matter. The latter must therefore be regarded as a highly excited metastable state.

The ${}^{113}\mathrm{I}$ nucleus has been studied using the ${}^{58}\mathrm{Ni}{(}^{58}\mathrm{Ni},3p)$ reaction at 250 MeV with the Gammasphere/Microball facility. Gamma-ray three- and four-fold data gated by charged particle combinations were analyzed. Multipolarities of the $\gamma$ rays were assigned following the angular correlation measurements. The present study is focused on the high spin properties, where the structure is dominated by $2p-2h$ excitations across the Z=50 gap. Ten decoupled bands showing the features of smooth band termination were observed; three of those bands are linked to known low-spin states, which allows the identification of configurations by direct comparisons with configuration-dependent cranked Nilsson-Strutinsky calculations. The yrast band, which was linked along with the signature partner, was followed up to ${(101/2\mathrm{}}^{+})$ and $ħ\omega \sim 1.3$ MeV. The other linked band was a negative-parity band observed up to ${(95/2\mathrm{}}^{-}).\mathrm{}$ Tentative configurations for the unlinked bands are discussed. Comparisons with the theoretical results suggest that the band built on a configuration involving the neutron $i_{13/2}$ intruder orbital originating from the N=6 harmonic oscillator subshell was observed in this experiment.

The recoil-distance Doppler-shift and Doppler-shift attenuation techniques were employed to determine for the first time lifetimes of high-spin states in ${}^{104}\mathrm{Cd}$ in the time range $0.3\hspace{0.5em}\mathrm{ps}<~\tau <~1.2\hspace{0.5em}\mathrm{ns}.$ The nuclei were populated using the compound nucleus reaction ${}^{58}\mathrm{Ni}{(}^{50}\mathrm{Cr},\hspace{0.5em}4p)$ and the γ radiation from their decay was detected with the GASP spectrometer. A total of 34 reduced transition probabilities and limits for 18 further transitions were extracted providing a rich basis for a comparison with theoretical calculations. In addition, the lifetime data contained new information urging for a revision of the published level scheme of ${}^{104}\mathrm{Cd}.$ In particular, a magnetic dipole band recently established and interpreted as magnetic rotation is shown to be not existing. The new experimental results in ${}^{104}\mathrm{Cd}$ are discussed in the frame of the interacting boson plus broken pair model.

Hyperdeformed (HD) states are described by dinuclear quasimolecular cluster configurations. They can be formed by heavy ion reactions. Optimum reaction partners, bombarding energies, and angular momenta are selected for finding these HD states. A new method to identify the populated HD states is suggested where γ transitions between the HD states are measured in coincidence with the decay of the nucleus into the cluster fragments. These experiments would prove whether the HD states can be described as cluster states.

Compton scattering cross sections from ${}^{12}\mathrm{C}$ have been measured at scattering angles of ${\theta }_{\gamma }=35\mathrm{}°-150°$ using tagged photons of $E_{\gamma }=84\mathrm{}-105$ MeV. Attempts to extract nucleon polarizabilities from the data were hampered by model ambiguities. These included uncertainties in the strength of the electric quadrupole and quasideuteron total photon absorption channels, and in the parametrizations of meson-exchange effects and nuclear form factors. These ambiguities led to large variations in the extracted values of the effective polarizabilities of the bound nucleon. Inelastic Compton scattering cross sections from the 4.44 MeV first-excited state were also obtained.

A comparison between nonrelativistic and relativistic descriptions of the ${(e,e}^{\prime }p)$ reaction is presented. We use the nonrelativistic DWEEPY code and develop a fully relativistic model starting from the effective Pauli reduction for the scattering state and the relativistic mean field theory for the bound state. Results for the ${}^{16}\mathrm{O}{(e,e}^{\prime }p)$ differential cross section and structure functions are compared in various kinematic conditions. A limit in energy of the validity of the nonrelativistic approach is established. The effects of spinor distortion and of the effective momentum approximation for the scattering state are discussed. A satisfactory agreement with data of differential cross sections, structure functions, and polarization observables is achieved.

In the context of the boson expansion theory, it is usually the case that the bosonization of single-boson (fermion) states is ignored. Although this is tolerable to some extent in cold systems, it causes serious difficulties in the treatment of thermal ensembles where the single-boson (fermion) density of states plays an important role. In the framework of the thermo-field dynamics it is shown how extended forms of the Holstein-Primakoff mapping for both bosons and fermions can lead to consistent thermal-boson expansions. Applications to the $O\left(N\right)\mathrm{}$ anharmonic oscillator and the Lipkin model are presented.

A new method to incorporate the Pauli principle into the double folding approach to the nucleus-nucleus potential is proposed. The description of the exchange terms at the level of the quasiclassical one-body density matrix is used. It is shown that in order to take into account the Pauli blocking properly, a redefinition of the density matrices of the free isolated nuclei must be done. A solution to the self-consistent incorporation of the Pauli blocking effects in the mean-field nucleus-nucleus potential is obtained in the Thomas-Fermi approximation.

Inclusive electron scattering data are presented for ${}^2\mathrm{H},$ C, Fe, and Au targets at an incident electron energy of 4.045 GeV for a range of momentum transfers from $Q^2=1\mathrm{}$ to $7\hspace{0.5em}(\mathrm{GeV}{/c)}^2.$ Data were taken at Jefferson Laboratory for low values of energy loss, corresponding to values of Bjorken $x\gtrsim 1.$ The structure functions do not show scaling in x in this range, where inelastic scattering is not expected to dominate the cross section. The data do show scaling, however, in the Nachtmann variable $\xi .$ This scaling appears to be the result of Bloom- Gilman duality in the nucleon structure function combined with the Fermi motion of the nucleons in the nucleus. The resulting extension of scaling to larger values of $\xi$ opens up the possibility of accessing nuclear structure functions in the high-$x$ region at lower values of $Q^2$ than previously believed.

An extended Lipkin-Meshkov-Glick model for testing the proton-neutron random-phase approximation $\left(pn\mathrm{RPA}\right)$ method is developed, taking into account explicitly proton and neutron degrees of freedom. Besides the proton and neutron single-particle terms two types of residual proton-neutron interactions, one simulating a particle-particle and the other a particle-hole interaction, are included in the model Hamiltonian so that the model is exactly solvable in an isospin $\mathrm{SU}\mathrm{}\left(2\right)\mathrm{}\otimes \mathrm{SU}\mathrm{}\left(2\right)\mathrm{}$ basis. The behavior of the first excited (collective) state obtained by (i) exact diagonalization of the Hamiltonian matrix and (ii) with the $\mathrm{pn}\mathrm{RPA}$ is studied as a function of the model parameters and the two results are compared with each other. Furthermore, charge-changing operators simulating nuclear beta decay and their action on eigenfunctions of the model Hamiltonian are defined and transition amplitudes of them are calculated using exact, the Tamm-Dancoff, and $\mathrm{pn}\mathrm{RPA}$ eigenfunctions.