Lifetimes were measured for the $2_1^{+}$, $4_1^{+}$, $0_2^{+}$, $1_1^{\mathrm{-}}$, and $3_1^{\mathrm{-}}$ levels in ${}_{}{}^{142,144,146}{}_{}{}^{}\mathrm{Ba}$ using a recently developed β-γ-γ fast timing method. In ${}_{}{}^{146}{}_{}{}^{}\mathrm{Ba}$, the ${\mathit{Q}}_0$ moment for the negative parity band was slightly larger than that for the positive parity band. The isovector E1 rates which were very small in ${}_{}{}^{146}{}_{}{}^{}\mathrm{Ba}$ and large in ${}_{}{}^{144}{}_{}{}^{}\mathrm{Ba}$ can be explained in terms of shell effects on the electric dipole moment. The new data are interpreted by both the spdf interacting boson and the reflection-asymmetric deformed shell models and provide compelling evidence for a static octupole deformation near ${}_{}{}^{146}{}_{}{}^{}\mathrm{Ba}$.

Inclusive quasielastic electron scattering by few-body systems, complex nuclei, and nuclear matter is analyzed in terms of y scaling using a nucleon spectral function which incorporates the momentum and removal energy distributions generated by two-nucleon correlations. It is demonstrated that binding effects play a relevant role in y scaling and that a qualitative interpretation of the available experimental data would require the simultaneous consideration of ground state correlations and final state interaction effects.

The imaginary part of the off-shell nucleon self-energy Σ(ω,k) in nuclear matter is investigated in the σω model using fourth-order contributions in the meson-nucleon couplings. We discuss contributions from particle-hole excitations, Pauli blocking of NN¯ excitations, and vacuum polarization to the various Lorentz components of the self-energy.

Constrained Hartree-Fock-Bogolyubov calculations have been performed to simulate the collision of two ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ nuclei at low energies (≊5.5 MeV/nucleon). These ab initio calculations indicate that electromagnetic transitions of energies between 1.5 and 1.8 MeV can be expected in the center of mass system of the colliding nuclei. These calculations are also consistent with the observed laboratory energy dependence and Z dependence of the anomalous pair production.

Differential cross section angular distributions for the ${}_{}{}^{6,7}{}_{}{}^{}\mathrm{Li}$(p,n${)}^{6,7}$Be reactions have been measured at energies between 60 and 200 MeV. The experimental angular distributions are analyzed using a microscopic distorted wave impulse approximation. The results of self-consistent microscopic distorted wave calculations based on a complete set of weak and electromagnetic data for the mass 6 and 7 systems are also presented. Total observed Gamow-Teller strength up to about 40 MeV excitation energy is reported. Energy dependence of the στ and τ effective interaction terms are presented up to 200 MeV. The measured (p,n) cross sections for the ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$ (g.s.) and ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$ (0.43 MeV) transitions are used to obtain the branching ratio of the ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$ (g.s.) decay to the g.s. and 0.478 MeV states in ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$. Zero degree polarization transfer (${\mathit{D}}_{\mathit{N}\mathit{N}}$) data at ${\mathit{E}}_{\mathit{p}}$=80, 120, 160, and 200 MeV are reported for the ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$(p,n${)}^6$Be (g.s.) and for the ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$(p,n${)}^7$Be (g.s.+0.43 MeV) reactions. Energy dependence of total and zero degree differential cross section for the ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$(p,n${)}^7$Be (g.s.+0.43 MeV) transitions are reported. Finally a comparison is presented for the (n,p), (p,p’), and (p,n) reaction in ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ populating isospin triplets.

It is shown that mutual interference cancellation of waves emitted by different two-body potentials can serve as a binding factor in continuous spectra of three-body systems. The nature of this effect is purely geometrical and it exists in wave functions of the same particular symmetry properties for all finite-range two-body interactions. At the same time this effect can manifest itself in the form of a real bound state or a resonance in the continuous spectrum only if the attraction is sufficiently strong. The wave function of such a state would fall off as a power of hyperradius. The possibility of this effect is proven for s and p waves of identical spinless bosons, and fermions with spin and isospin equal to 1/2.

The impact of models for E1 and M1 gamma-ray strength functions on the results of nuclear model calculations of total average radiation widths, radiative capture cross sections, and gamma-ray spectra has been studied. We considered strength functions that reproduce photoabsorption and/or average resonance data but significantly differ from each other at low gamma-ray energies. As the calculated quantities critically depend on the strength functions in this energy region, model calculations can be used to test the low-energy behavior of strength functions. By analyzing the ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$, ${}_{}{}^{143}{}_{}{}^{}\mathrm{Nd}$, ${}_{}{}^{105}{}_{}{}^{}\mathrm{Pd}$, and ${}_{}{}^{93}{}_{}{}^{}\mathrm{Nd}$ neutron capture reactions we found strong evidence for a model of the E1 strength function, which is characterized by the following properties: (i) an energy dependent spreading width of the underlying Lorentzian for the photoabsorption cross section and (ii) a nonzero, temperature dependent, limit as the transition energy tends to zero. This model is founded in theoretical work by Zaretskij, Sirotkin, and Kadmenskij and represents a partial breakdown of Brink’s hypothesis.

The ${}_{}{}^{30}{}_{}{}^{}\mathrm{Si}$${(}^3$He,d${)}^{31}$P reaction has been investigated at 25 MeV incident energy. About 80 levels were observed up to an excitation energy of 10 MeV by using a split-pole magnetic spectrograph. Most of the proton-unbound states were identified with resonance levels observed in proton capture reactions on ${}_{}{}^{30}{}_{}{}^{}\mathrm{Si}$. Four levels were observed for the first time in a reaction which couples a proton to a ${}_{}{}^{30}{}_{}{}^{}\mathrm{Si}$ core. Spectroscopic information has been obtained for about 60 levels through angular distribution measurements and distorted wave Born approximation analyses, with special treatment applied in the cases of the proton-unbound states. The spectroscopic factors of the proton-unbound states are in overall agreement with the spectroscopic factors which are deduced from the proton partial widths measured in resonant proton scattering experiments, but the proton partial width which is obtained in this work for the 7897 keV level is in disagreement with previous values from γ-ray resonant absorption measurements. The strengths of the l=0, 2, and 3 transfers are essentially concentrated into one level, each of isospin T=1/2 and T=3/2. In contrast the l=1,T=1/2, strength is distributed over many levels, especially in a cluster of six levels between 9.0 and 9.8 MeV. The sum rule for the 2${\mathit{p}}_{3/2}$,T=1/2, proton single-particle strength is exhausted, leading to a centroid energy of about 7.9 MeV for this configuration. Isospin assignments are discussed for some levels. The excitation energies and spectroscopic factors for even-parity states are compared with the results of a recent, complete sd-shell space, shell-model calculation.

The results of a new resonance analysis of the elastic scattering of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ by ${}_{}{}^3{}_{}{}^{}\mathrm{H}$ in odd-parity states and the radiative capture of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ by ${}_{}{}^3{}_{}{}^{}\mathrm{H}$ in the first excited state of ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ are presented. We give evidence for a very broad level of ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ at ${\mathit{E}}_{\mathrm{Li}}$=26.59±0.065 MeV with ${\mathit{J}}^{\mathrm{\pi }}$=$2^{\mathrm{-}}$, S,T=1,1 not previously reported. The shape of the angular distributions and the broad maximum observed in the radiative capture cross section at high energies are explained in terms of the interference of three very wide ${}_{}{}^{33}{}_{}{}^{}$${\mathit{F}}_{\mathit{j}}$ overlapping resonances. Numerical values of the resonance parameters are given.

The differential cross sections for the (p,n) reaction to the ground-state and first $2^{+}$ excited analogs of the four even palladium isotopes (104, 106, 108, and 110) have been measured at a proton bombarding energy of 26 MeV. Integrated cross sections for the analog states deviate from the linear dependence on neutron excess as was previously found in other sets of isotopes, e.g., the molybdenum and zirconium isotopes. The observed dependence on deformation of the ground-state analog transition is in quantitative agreement with calculations, which include the inelastic couplings originally used to explain the molybdenum results. Detailed ten-coupled-channels calculations including the ground state, the one- and two-quadrupole phonon collectives states in Pd, and their analogs in Ag give excellent agreement simultaneously with proton elastic scattering, proton inelastic scattering to the first $2^{+}$ state, ground-state analog transitions, and $2^{+}$ analog-state transitions. The effect of the one-step isovector deformation was too small to be extracted from these data.

The atomic mass excesses of ${}_{}{}^{200}{}_{}{}^{}\mathrm{Pb}$, ${}_{}{}^{204}{}_{}{}^{}\mathrm{Po}$, ${}_{}{}^{208}{}_{}{}^{}\mathrm{Rn}$, ${}_{}{}^{212}{}_{}{}^{}\mathrm{Ra}$, and ${}_{}{}^{216}{}_{}{}^{}\mathrm{Th}$ were determined to be -26.262±0.015, -18.352±0.015, -9.667±0.015, -0.208±0.015, and 10.287±0.017 MeV, respectively. They were obtained from the measured Q value of -28.043±0.013 MeV for the ${}_{}{}^{204}{}_{}{}^{}\mathrm{Pb}$(α${,}^8$He${)}^{200}$Pb (g.s.) reaction and the known alpha-decay Q values. The results were compared with some predicted values.

The spectral continua ${\mathit{E}}_{\mathit{n}}$≥30 MeV of neutrons from the reactions ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$, ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$, ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$(p,xn) have been measured for ${\mathit{E}}_{\mathit{p}}$=120 and 160 MeV and angles 0°≤θ≤145°. Angular distributions can be explained quantitatively in absolute values and shapes over five orders of magnitude as statistical multistep direct emission in which up to six steps are involved with significant contributions. The strength ${\mathit{V}}_0$ of the effective nucleon-nucleon interaction applied shows a systematic dependence on the projectile energy ${\mathit{E}}_{\mathit{p}}$≤160 MeV that is consistent with that of spectroscopic factors for single step distorted-wave Born approximation results for transitions to low-lying states. The data also agree well with predictions of a recent phenomenological parametrization.

The potentials for ${}_{}{}^{12}{}_{}{}^{}\mathrm{-}_{}^{12}{}_{}{}^{}$C scattering at 360, 1016, 1449, and 2400 MeV are obtained by inversion of S functions of an absorption model of scattering. The parameters of those S functions were determined by fitting the elastic scattering differential cross sections. A semiclassical inverse scattering method at fixed energy was used to produce potentials uniquely related to the S functions in the so-called sensitive radial regions around the strong absorption radii, potentials which do not depend upon an assumed shape. Comparison of the inversion potentials with those obtained by optical model potential fits to data show close agreement in the sensitive regions. It is emphasized that inversion is an easily performed, more systematic, method of analysis of intermediate energy heavy-ion scattering data than the usual optical model approach having the additional advantage of model independence.

Optical-model analyses have been performed with an optical-model code for ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$${+}^{12}$C elastic scattering in the center-of-mass energy range ${\mathit{E}}_{\mathrm{c}.\mathrm{m}.\mathrm{}}$=35–63 MeV. A total of 125 parameter sets have been found and a taxonomy of potential families is proposed on the basis of volume integrals and rms radii. To complement this study four parameter sets at ${\mathit{E}}_{\mathrm{lab}}$=81 and 100 MeV for ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$${+}^{12}$C found in a previous report are also discussed. Conventional Woods-Saxon parameters of different real well depth and with either a volume or surface absorption predict the observed differential cross sections at six energies in the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$${+}^{12}$C case. The potentials found form discrete families corresponding to the quantum mechanical requirement for the allowed number of wavelengths of distorted waves in the interior region of the potential. Excitation functions for ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$${+}^{12}$C elastic scattering were calculated with these parameters in the center-of-mass energy range ${\mathit{E}}_{\mathrm{c}.\mathrm{m}.\mathrm{}}$=15–95 MeV and four families of potentials of different real well depth predict gross structure at 90° that persists undiminished throughout this energy range. Inspection of the predicted cross-section surface shown as a function of energy and angle revealed important features which are in good qualitative agreement with experiment. Color contour visualizations of such surfaces gave new insights into the regularity of cross-section structures in different angular regions.

Levels in ${}_{}{}^{76}{}_{}{}^{}\mathrm{Br}$ have been populated through the ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ti}$${(}^{32}$S,3pn) reaction at 106 MeV. The yrast (K=$4^{+}$) band has been extended to angular momentum 21ħ. Lifetimes were measured for seven levels by means of the Doppler shift attenuation method. Above the ${10}^{+}$ level the band behaves as a near-rigid rotor. The measured B(E2) values are observed to decrease with increasing rotational frequency.

Angular distributions of fragments emitted in the reaction ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}$${+}^{63}$Cu measured in the range ${\mathrm{\theta }}_{\mathrm{lab}}$=10° to 120° at incident energy between 100 to 108 MeV (lab) have been analyzed according to available models for deep inelastic collisions with the aim to evidence different mechanisms contributing to such reactions. The analysis was performed in the framework of Strutinsky model taking into account both the development of Kun and of Abul-Magd and Simbel. To determine the interaction times, previously published excitation functions were also analyzed in the framework of Kun’s model of cross section statistical fluctuations and near-side and far-side scattering were taken into account separately. It was pointed out that the rotational energy dissipation occurs in a limited angular range around the grazing angle. The presence of two distinct reaction mechanisms, each of them characterized by an interaction time, was also evidenced by comparing the energy averaged angular distributions to the Abul-Magd and Simbel model for dissipative collisions.

The ${}_{}{}^{150}{}_{}{}^{}\mathrm{Nd}$${(}^{35}$Cl,4n${)}^{181}$Ir and ${}_{}{}^{150}{}_{}{}^{}\mathrm{Nd}$${(}^{34}$S,4n${)}^{180}$Os reactions have been used to study the lifetimes of high-spin states in ${}_{}{}^{181}{}_{}{}^{}\mathrm{Ir}$ and ${}_{}{}^{180}{}_{}{}^{}\mathrm{Os}$ using the recoil-distance technique. The lifetimes of four states in ${}_{}{}^{181}{}_{}{}^{}\mathrm{Ir}$ and three yrast states in ${}_{}{}^{180}{}_{}{}^{}\mathrm{Os}$ have been determined. The mean weighted values of quadrupole moments deduced for the measured rotational transitions between yrast states in ${}_{}{}^{181}{}_{}{}^{}\mathrm{Ir}$ and ${}_{}{}^{180}{}_{}{}^{}\mathrm{Os}$, ${\mathit{Q}}_0$=(6.0±0.2) e b and ${\mathit{Q}}_0$=(6.1±0.4) e b, respectively, are equal within experimental errors.

Continuum γ-ray spectra and angular distributions from decays of highly excited ${}_{}{}^{39}{}_{}{}^{}\mathrm{K}$, ${}_{}{}^{40}{}_{}{}^{}\mathrm{K}$, ${}_{}{}^{42}{}_{}{}^{}\mathrm{Ca}$, and ${}_{}{}^{45}{}_{}{}^{}\mathrm{Sc}$ compound nuclei produced by bombarding ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$ with ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{15}{}_{}{}^{}\mathrm{N}$, and ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$ ions have been measured and the giant-dipole-resonance strength function has been extracted. The effective temperature associated with the states upon which the giant dipole resonance is built is nearly constant (1.7–1.8 MeV) for these reactions, while the final average spin varies from 8 to 18.5ħ as the projectile energy varies from 32 to 72.5 MeV. The parameters of the giant-dipole-resonance strength function extracted from fits of statistical model calculations to the γ-ray spectra measured at ${\mathrm{\theta }}_{\gamma }$=90° provide direct information on the spin dependence of the hot nuclear shape. The mean energy of the giant dipole resonance shows a weak spin dependence that has a different character for ${}_{}{}^{39}{}_{}{}^{}\mathrm{K}$ and ${}_{}{}^{45}{}_{}{}^{}\mathrm{Sc}$ nuclei. The width of the giant dipole resonance increases rapidly with spin for all reactions studied, from 11.6±0.3 MeV at 8ħ to 14.7±0.5 MeV at 18.5ħ for ${}_{}{}^{45}{}_{}{}^{}\mathrm{Sc}_{}^{\mathrm{*}}{}_{}{}^{}$ at ${\mathit{T}}_{\mathit{f}}$=1.7–1.8 MeV, for example, presumably due to rotational broadening of the giant dipole resonance. For the reactions ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$${+}^{27}$Al at ${\mathit{E}}_{\mathrm{lab}}$=62.7 MeV and ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$${+}^{27}$Al at ${\mathit{E}}_{\mathrm{lab}}$=44.9 and 72.5 MeV, angular distributions have been measured. The observed energy dependence of the ${\mathit{a}}_2$ coefficient suggests large nuclear deformation consistent with oblate noncollective or prolate collective rotation. The level density in nuclei with A≃40 has been calculated in the Reisdorf approach with parameters fitted to low-energy level density data for nuclei in this mass region.

Excitation functions have been measured for isotopes of Bk, Cf, Es, and Fm produced from the interactions of 207- to 286-MeV ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$ ions with ${}_{}{}^{248}{}_{}{}^{}\mathrm{Cm}$. The measured isotopic distributions were found to be essentially symmetric with full widths at half maximum between 2.0 and 3.5 mass units. These results are comparable to those obtained in previous studies using ${}_{}{}^{40,44,48}{}_{}{}^{}\mathrm{Ca}$ with ${}_{}{}^{248}{}_{}{}^{}\mathrm{Cm}$. The maxima of the isotopic distributions from the ${}_{}{}^{40}{}_{}{}^{}\mathrm{-}_{}^{248}{}_{}{}^{}$Cm system show shifts, to both heavier and lighter mass numbers, of 0 to 2 mass units relative to the corresponding maxima of the isotopic distributions from the ${}_{}{}^{40,44,48}{}_{}{}^{}\mathrm{-}_{}^{248}{}_{}{}^{}$Cm systems.

A model for studying fragmentation phenomena is proposed and developed. The model leads to a single, simple, and exact expression for the cluster size distribution function. Various limits of this distribution function show: (1) evaporation-like behavior, (2) scale-invariant power law behavior, (3) a broad region with a dependence which is linear growth in small clusters and exponential falloff of large clusters and, finally, (4) total multifragmentation with an exponential-like falloff of all clusters except the monomer or unit element. The cluster size distribution function in any region is given by various limits of one expression: ${\mathit{Y}}_{\mathit{A}}$(k,x)={A!/[k!(A-k)!]}xB(x+A-k,k). Here, the size k is the number of elements in a cluster taken from a fixed total number of A elements, x is an evolutionary tuning parameter which determines the various regions, and B(x+A-k,k) is a beta function. Cellular rules and a particular choice of weight function lead to self-similar behavior on Young’s triangular lattice. A scale invariant hyperbolic power law emerges in a row by row evolution of the lattice. A counterclockwise rotation of Ferrer’s block diagram of partitions shows a pictorial resemblance of the present model with recent work on self-organized critical states, and a comparison is made. The cumulative mass distribution at a critical point of the model is a staircase function whose continuous limit is analogous to that of a uniform bar. The uniform bar may then be hammered into various shapes which will be discussed. Some observations on the form of x are given by comparing the multifragmentation limit of the model with the law of mass action or Saha equation. The evaporation limit of the model is discussed and evaporation barriers are shown to evolve into binding energy enhancement factors in the Saha equation.