The SU(3)×SU(4) symmetry limit appropriate for a pseudo-orbit pseudospin k=1 i=(3/2 decomposition of the single particle angular momenta j=(1/2, (3/2, and (5/2, incorporated in the recently suggested fermion dynamical symmetry model, is discussed for the case of degenerate protons and neutrons. A comparison of the corresponding states with realistic sd shell wave functions is used to determine the validity of the symmetry for rotational even-even nuclei in this region. ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ is well described, with a single representation accurately reproducing both high and low spin members of the ground band, while ${}_{}{}^{22}{}_{}{}^{}\mathrm{Ne}$ and ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$ display strong symmetry breaking. It is shown that a scheme based on k-i basis intrinsic states accounts for the success in ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$.

The fragmentations of the five proton hole states, 3$s_{1/2}$, 2$d_{3/2}$, 1$h_{11/2}$, 2$d_{5/2}$, and 1$g_{7/2}$, in ${}_{}{}^{207}{}_{}{}^{}\mathrm{Tl}$ and ${}_{}{}^{205}{}_{}{}^{}\mathrm{Tl}$ are calculated in terms of the coupling of these states with the collective vibrational states in ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ and ${}_{}{}^{206}{}_{}{}^{}\mathrm{Pb}$, respectively. Good overall agreement is observed between the experimental and theoretical results. The calculated occupancy of the 3$s_{1/2}$ state in ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ is n(208)=0.94, as compared to the (e,e’p) reaction result n(208)=0.83(9) and the (d${,}^3$He) reaction result n(208)=0.92(13). Several weak ($S_j$≤0.02) 3$s_{1/2}$ states are predicted in ${}_{}{}^{207}{}_{}{}^{}\mathrm{Tl}$ and ${}_{}{}^{205}{}_{}{}^{}\mathrm{Tl}$.

In the present article, we study systematically the influence of different types of perturbations on the ${\mathrm{SU}}^{\mathrm{*}}$(3) dynamical symmetry. Both a Majorana perturbation, a d-boson energy perturbation, and the ${\mathrm{SU}}^{\mathrm{*}}$(3)→O(6) and ${\mathrm{SU}}^{\mathrm{*}}$(3)→SU(3) transitions are considered. In all cases, we study the variation of the ground and gamma bands as well as some important electromagnetic transitions, in particular the B(M${1;1}_1^{+}$→$0_1^{+}$) value. Even if the present calculations start from a simple Hamiltonian (a consistent Q Hamiltonian), the results can be of interest for the study of the Xe, Ba A≃130 mass region, the Ru, Pd A≃100 mass region, and the Pt, Os A≃190 mass region.

In the present article, we discuss the Xe and Ba nuclei in the A≃130 mass region. This mass region has been shown to constitute a new region of O(6)-like nuclei. A number of deviations, however, from a pure O(6) dynamical symmetry are experimentally observed, in particular the energy staggering in the gamma band. Here, we study the influence of triaxial perturbations, i.e., introducing terms in the Hamiltonian that are of ${\mathrm{SU}}^{\mathrm{*}}$(3) type, on the energy spectra of the ${}_{}{}^{124\mathrm{-}130}{}_{}{}^{}\mathrm{Xe}$ and of the ${}_{}{}^{128\mathrm{-}134}{}_{}{}^{}\mathrm{Ba}$ nuclei. We also address the problem of B(E2) transitions, connecting the $2_{\gamma }^{+}$, $3_{\gamma }^{+}$, $4_{\gamma }^{+}$, $5_{\gamma }^{+}$, and $0_3^{+}$ levels to the ground state and the gamma band.

We show that the method based on the tensor coupling of an appropriate family of isovector excitation operators to the parent isospin multiplet can be used to advantage for the correct treatment of the isospin degree of freedom in nonisoscalar nuclei. This method is applicable to any isovector excitation operator and for parent states which need not be of the closed subshells type. As an illustration we apply it to the study of the Gamow-Teller transition strength in ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$.

In this paper we present a nonrelativistic microscopic mean-field framework for finite nuclei in which the nucleus is described as a system of A baryons where each baryon is a dynamically determined superposition of a nucleon (N) and a Δ(3,3) resonance. The N-N interaction is a Brueckner G matrix based on the Reid soft-core interaction while the N-Δ transition potentials and Δ-Δ interactions are one-boson-exchange potentials. The ground-state properties of the nuclei ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ and ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ are determined within the spherical Hartree-Fock approximation in a no-core basis consisting of up to six major oscillator shells. A detailed study of the zero-temperature properties of these nuclei under compression and dilation is presented in order to gain insight into the nuclear equation of state. Under certain conditions, a transition to a mixture of nucleons and deltas is found in ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ but not in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$. The transition is reminiscent of a first-order phase transition.

The starting point for most studies of large amplitude collective motion in nuclear physics, the time-dependent Hartree-Fock equations, can be mapped to a problem in classical Hamiltonian mechanics, which is the form of the problem studied in this work. For a system with N degrees of freedom, collective motion is identified with motion completely confined to a surface in K<N dimensions. Conditions for the existence of such decoupled surfaces are worked out and a procedure for constructing them is formulated. For most practical problems, where such surfaces do not strictly exist, a concept of approximate decoupling is developed and a test of its accuracy is described. Our results generalize the method of maximum global decoupling found in the earlier literature.

The classical theory of large amplitude collective motion described in a previous paper is applied to a model with three degrees of freedom, in which the potential energy function has landscape features such as a valley which provides the easiest means, both classically and quantum mechanically, for a ‘‘particle’’ to escape from the center of the potential, a local minimum, to the ‘‘outside world.’’ We analyze exhaustively the problem of decoupling two collective degrees of freedom from the original three coordinates. We compute the two-dimensional surface to which the collective motion is (approximately) confined. This function in turn determines the collective Hamiltonian. We suggest and apply various criteria for measuring the goodness of the decoupling, and achieve a clear understanding of the domain of applicability of the analysis.

The coherent production of pions in the ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$${(}^3$He,${\mathrm{\pi }}^{\mathrm{-}}$${)}^{211}$At reaction was measured radiochemically using activation techniques near the physical pion threshold at energies of 158–270 MeV. Above threshold, the total cross sections were measured in the 1–10 nb range. A theoretical fit of the summed total cross section into all particle bound states was made using the two-nucleon model of Dillig with appropriate two-body scaling of the momentum transfer.

Differential cross sections and analyzing powers for the ${}_{}{}^7{}_{}{}^{}(\mathrm{p}\to$,${\pi }^{+}$) reaction at $T_{\mathrm{p}}$=250, 354, and 489 MeV leading to three excited states of ${}_{}{}^8{}_{}{}^{}\mathrm{Li}$ are presented and are compared with previously published 200 MeV data. The differential cross sections at constant four-momentum transfer for two of the states exhibit an enhancement at approximately the ${\Delta }_{1232}$ invariant mass, and shapes of the analyzing power angular distributions for these states exhibit a characteristic p→p→d${\pi }^{+}$ signature. Quite different dependences are observed for the third state.

The lifetimes of the gamma-ray continuum at spins above 40ħ were measured in ${}_{}{}^{152}{}_{}{}^{}\mathrm{Dy}$ via the Doppler shift attenuation technique following the ${}_{}{}^{74}{}_{}{}^{}\mathrm{Ge}$${(}^{80}$Se,2n) and ${}_{}{}^{76}{}_{}{}^{}\mathrm{Ge}$${(}^{80}$Se,4n) reactions, at beam energies of 285 and 320 MeV, respectively. Although the deduced average quadrupole moments are smaller than the value expected for superdeformed bands, the variation of the observed Doppler shift as a function of gamma-ray energy suggests that both small deformation (β∼0.2) and more deformed structures (possibly superdeformed) are present in the very high spin continuum of this nucleus.

Velocity and angular distributions of projectile-like fragments were measured between ${\theta }_{\mathrm{lab}=0\mathrm{}}$° and 4° (inside the grazing angle) for the ${}_{}{}^{40}{}_{}{}^{}$Ar${+\mathrm{}}^{208}$Pb system at 60 MeV/nucleon using a magnetic spectrometer. Velocity spectra are similar to those obtained at larger angles, while the angular distributions, very forward peaked for light nuclei, tend to become flat for the heaviest fragments. The influence of the Coulomb and nuclear deflection of the fragments is discussed.

It is shown that the recently measured ${}_{}{}^{54}{}_{}{}^{}\mathrm{Fe}$(n,p${)}^{54}$Mn reaction together with the ${}_{}{}^{54}{}_{}{}^{}\mathrm{Fe}$(p,n${)}^{54}$Co reaction provide information about the quenching of Gamow-Teller strength due to random-phase approximation correlations.

The coupling between the isoscalar and isovector monopole resonances in N≠Z nuclei is considered in the framework of the random phase approximation. We find that the one-body operator ${\mathit{F}}_1$=2[${\mathrm{\Sigma }}_{\mathrm{n}}$(Z/A)${\mathit{r}}_{\mathrm{n}}^2$-${\mathrm{\Sigma }}_{\mathrm{p}}$(N/A)${\mathit{r}}_{\mathrm{p}}^2$], different from the operator F${\mathrm{̃}}_1$=${\mathrm{\Sigma }}_{\mathit{i}}^{\mathit{A}}$${=}_1$${\mathit{r}}_{\mathit{i}}^2$${\mathrm{\tau }}_{\mathit{i}}^{\mathit{z}}$ usually empoloyed in the literature, gives rise to excitations which are in practice decoupled from the ones generated by the isoscalar operator ${\mathit{F}}_0$=${\mathrm{\Sigma }}_{\mathit{i}}^{\mathit{A}}$${=}_1$${\mathit{r}}_{\mathit{i}}^2$. The consequences on the average excitation energy of the monopole resonance and on various sum rules are discussed.

Spectral distribution studies are done using Wildenthal’s highly successful universal sd interaction for binding energies, excitation spectra, and occupancies for nuclei in the sd shell, and comparisons are made with shell model as well as experimental values.

Within a multiple collision theory based on the eikonal approximation we study the ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$(p,n${)}^{90}$Nb 0° cross section at 200 MeV incident proton energy. Both the one- and two-step contributions are calculated and compared to the experimental inclusive cross section. Good agreement between theory and experiment is found. Possible implications for the ‘‘missing Gamow-Teller strength’’ are discussed.

We analyze the treatment of Cheung and Machleidt and show that the essential physics is the same as in our previous approach. Thus their work using a detailed model confirms the essence of our findings.

Using phosphate glass detectors capable of withstanding a background dose of ∼${10}^{14}$ alpha particles per ${\mathrm{cm}}^2$, we have searched for rare decay modes of ${}_{}{}^{241}{}_{}{}^{}\mathrm{Am}$ involving emission of energetic heavy ions. Predictions of the branching ratio for ${}_{}{}^{34}{}_{}{}^{}\mathrm{Si}$ emission relative to alpha decay of ${}_{}{}^{241}{}_{}{}^{}\mathrm{Am}$ range from 4×${10}^{-13\mathrm{}}$ to 4×${10}^{-16\mathrm{}}$. In a six-month exposure to 8 mg of ${}_{}{}^{241}{}_{}{}^{}\mathrm{Am}$, with detectors subtending a solid angle of 2.51 sr, we detected no particles with $12\le Z\le 16$, from which we infer an upper limit ($2\sigma$) of 7.4×${10}^{-16\mathrm{}}$.

The angular momentum dependence of large fragment production in long lived reactions is studied by measurements of fragment cross sections from reactions with substantially different angular momentum distributions and the coincident $\gamma$-ray multiplicity distributions. The results indicate that the primary $l$-wave distributions move to larger mean values and decrease in width and skewness with increasing mass symmetry in the decay channel. The results also confirm that the partition of angular momentum in kinetic energy relaxed heavy-ion reactions is that expected for a rigidly rotating intermediate.