Gamma-ray spectra from the decay of the giant dipole resonance (GDR) built on excited states of ${}_{}{}^{92}{}_{}{}^{}\mathrm{Mo}$ and ${}_{}{}^{100}{}_{}{}^{}\mathrm{Mo}$ nuclei at average spins (9–24)ħ and temperatures of 1.35–1.50 MeV were measured, and the parameters of a two-component GDR strength function were extracted. Deformations determined from the fitted component energies are substantially larger than predicted by the rotating liquid drop model, suggesting large thermal shape fluctuations. Widths of the GDR in ${}_{}{}^{92}{}_{}{}^{}\mathrm{Mo}$ increase from 7.6±0.1 to 8.6±0.2 MeV in the spin range of (9–19.5)ħ and temperature range of 1.35–1.45 MeV, as compared with the ground-state GDR width of 5.4±0.2 MeV. In ${}_{}{}^{100}{}_{}{}^{}\mathrm{Mo}$ the GDR width is nearly constant and equals 9.8±0.2, 9.9±0.2, and 10.1±0.2 MeV at average spins 9ħ, 19.5ħ, and 24ħ and temperatures 1.35, 1.45, and 1.50 MeV, respectively, as compared with the ground-state width of 7.9±0.2 MeV. The observed difference in the GDR widths between the two molybdenum isotopes at the same temperatures and spins indicates that shell effects are still present at the temperatures studied.

A search for continuum levels in ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ with a large ${[}^{16}$O($0_2^{+}$)+α] parentage has been conducted using both resonant and direct production processes. The differential cross section for the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$(α,${\mathrm{\alpha }}_1$${)}^{16}$${\mathrm{O}}^{\mathrm{*}}$($0_2^{+}$) reaction has been measured at 13 to 26 angles for bombarding energies from ${\mathit{E}}_{\mathrm{\alpha }}$=10.2 to 18 MeV, mostly in 25 keV steps. Events leading to the first excited state in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ were identified by requiring the coincident observation of an α particle and an electron or positron from the internal pair decay of the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ first excited state. Amplitudes of individual partial waves were extracted from the data by parametrizing the angular distributions in terms of the complex zeros of the scattering amplitudes. An R-matrix analysis of the data reveals a ${\mathit{J}}^{\mathrm{\pi }}$=$2^{+}$ level at ${\mathit{E}}_{\mathit{x}}$=13.1 MeV with a spectroscopic factor ${\mathrm{\Theta }}_{\mathrm{\alpha }1}^2$>63%.

Several individual levels, a region of overlapping ${\mathit{J}}^{\mathrm{\pi }}$=$4^{+}$ levels from ${\mathit{E}}_{\mathit{x}}$=13.69 to 14.93 MeV and a region of ${\mathit{J}}^{\mathrm{\pi }}$=$6^{+}$ levels from ${\mathit{E}}_{\mathit{x}}$=16.73 to 18.73 MeV, have also been analyzed in detail. Branching ratios of ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ levels to the first excited state in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ have been measured by populating the levels with the reaction ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$${(}^{12}$C,α${)}^{20}$${\mathrm{Ne}}^{\mathrm{*}}$ and observing their subsequent α decay to the $0_2^{+}$ state of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$. A ${\mathit{J}}^{\mathrm{\pi }}$=$6^{+}$ level at ${\mathit{E}}_{\mathit{x}}$=15.16 MeV and a ${\mathit{J}}^{\mathrm{\pi }}$=$8^{+}$ level at ${\mathit{E}}_{\mathit{x}}$=18.54 MeV, which had previously been suggested as members of a rotational band based on the ${\mathit{J}}^{\mathrm{\pi }}$=$0^{+}$ level in ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ at ${\mathit{E}}_{\mathit{x}}$=12.44 MeV are shown to have small values of ${\mathrm{\Theta }}_{\mathrm{\alpha }1}^2$, arguing against this identification.

By using the ${}_{}{}^{77}{}_{}{}^{}\mathrm{Se}$(t,p${)}^{79}$Se reaction at 17 MeV, angular distributions have been measured for transitions leading to 34 states or groups of states in ${}_{}{}^{79}{}_{}{}^{}\mathrm{Se}$ up to an excitation energy of approximately 3.2 MeV. Twelve of these states are reported for the first time. Comparisons with distorted-wave Born-approximation calculations have allowed the L transfer for most of the transitions observed to be determined. Four L=0 transitions are seen, leading to assignments of ${\mathit{J}}^{\mathrm{\pi }}$=1/$2^{\mathrm{-}}$ to the states populated. The ${\mathit{J}}^{\mathrm{\pi }}$ values for the majority of the other final states have been restricted to one of two values.

New data for elastic and inelastic ${\mathrm{\pi }}^{+}$ and ${\mathrm{\pi }}^{\mathrm{-}}$ scattering by ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ at 180 MeV are presented. The elastic scattering data were analyzed with a standard Kisslinger potential in a coordinate space (r space) calculation using the free π-N amplitudes to calculate the potential coefficients. Momentum-space (p-space) calculations were also performed using the free π-N amplitudes to calculate on-shell matrix elements and the Landau-Tabakin model for the off-shell. The same ground-state proton and neutron densities were used in these two spaces and the fits are good. The distorted-wave impulse approximation calculations in both spaces, with the same collective model transition densities, reproduce the inelastic differential cross sections quite well. The proton and neutron transition multipole matrix elements and their ratios were calculated from the deformation parameters extracted from fits to inelastic scattering data. It is found that the ratios calculated in these two spaces are quite close to each other and close to those found in a comparison of (e,e’) and (p,p’) experiments, while the absolute value of matrix elements found in the p-space calculations are ∼15–20 % smaller than those from the r-space calculations. The r-space proton matrix elements are generally in good agreement with those obtained from electron scattering. The effects of the pion-nucleon interactions and form factors used in these calculations were investigated.

High-spin states have been populated in odd-odd ${}_{}{}^{186,188}{}_{}{}^{}\mathrm{Au}$ via the heavy-ion ${}_{}{}^{171,173}{}_{}{}^{}\mathrm{Yb}$${(}^{19}$F,4n) reactions at 93–94 MeV. Rotational bands built on ${11}^{\mathrm{-}}$ oblate ν${\mathit{i}}_{13/2}^{\mathrm{-}1}$⊗π${\mathit{h}}_{11/2}^{\mathrm{-}1}$ structures have been observed in both nuclei, similar to those reported in ${}_{}{}^{190\mathrm{-}194}{}_{}{}^{}\mathrm{Au}$. Two new strongly coupled bands in ${}_{}{}^{186}{}_{}{}^{}\mathrm{Au}$ are interpreted as prolate π${\mathit{h}}_{9/2}$⊗ν${\mathit{i}}_{13}$2 and π${\mathit{i}}_{13/2}$⊗ν${\mathit{i}}_{13/2}$ configurations. Based on blocking arguments a band crossing in the latter structure is attributed to the alignment of ${\mathit{h}}_{9/2}$ protons. Measured B(M1;I→I-1)/B(E2;I→I-2) ratios are compared to predictions of the Dönau and Frauendorf geometrical formalism extended to odd-odd cases.

Low-lying low-spin collective states in even ${}_{}{}^{106\mathrm{-}112}{}_{}{}^{}\mathrm{Cd}$ and ${}_{}{}^{116}{}_{}{}^{}\mathrm{Cd}$ were investigated using in-beam and off-beam γ-ray and conversion-electron spectroscopy. New spin assignments and decay branching ratios for the levels in ${}_{}{}^{106}{}_{}{}^{}\mathrm{Cd}$, ${}_{}{}^{108}{}_{}{}^{}\mathrm{Cd}$, ${}_{}{}^{110}{}_{}{}^{}\mathrm{Cd}$, and ${}_{}{}^{112}{}_{}{}^{}\mathrm{Cd}$ were obtained. The present results essentially complement the level systematics from ${}_{}{}^{106}{}_{}{}^{}\mathrm{Cd}$ to ${}_{}{}^{120}{}_{}{}^{}\mathrm{Cd}$. From the new data, it is inferred that two sets of low-lying $0^{+}$ states having different excitation characteristics cross between ${}_{}{}^{114}{}_{}{}^{}\mathrm{Cd}$ and ${}_{}{}^{116}{}_{}{}^{}\mathrm{Cd}$. No corresponding crossing occurs on the neutron deficient side. New evidence for the existence of the proton-intruder states has been found.

In this paper various realistic shell model effective interactions are analyzed in terms of their central, vector, and tensor components. The effective forces were obtained from phenomenological (Hamada-Johnston) as well as from modern meson-exchange (Bonn-Jülich and Paris) nucleon-nucleon potentials and were calculated to various approximations within the framework of perturbation theory. For all forces examined, the dominant contribution comes from the central part. The vector component is small for the bare G-matrix interaction, especially for T=0, but is considerably modified by renormalization. The tensor component is somewhat larger than the vector component and is relatively larger for the Hamada-Johnston potential than for the Bonn-Jülich and Paris potentials. Centroids in j-j and SU(3) coupling were obtained with and without noncentral contributions; considerable sensitivity was observed in the SU(3) basis.

A numerical study of the static and dynamical properties of the pairing interaction in a two-level system is presented as a search for a large-N scaling behavior already empirically found in other models of the same class. A scaling behavior is found in the spectra as a function of N, but the dynamical properties show strong dependence on the initial conditions.

Cross sections, parallel and perpendicular momentum transfers, charge loss, and velocity systematics are presented for fission following reactions of Fe and Nb projectiles at 50–100 MeV/nucleon on targets of Ta, Au, and Th. Data are compared to simple models for peripheral heavy ion collisions.

A detailed deexcitation calculation is presented for target residues resulting from intermediate-energy heavy ion reactions. The model involves an intranuclear cascade, subsequent fast nucleon emission, and final decay by statistical evaporation including fission. Results are compared to data from bombardments with Fe and Nb projectiles on targets of Ta, Au, and Th at 100 MeV/nucleon. The majority of observable features are reproduced with this simple approach, making obvious the need for involving new physical phenomena associated with multifragmentation or other collective dissipation mechanisms.

Measurements of the analyzing power for the ${}_{}{}^{13}{}_{}{}^{}\to$(${\mathrm{\pi }}^{\pm }$,${\mathrm{\pi }}^{\pm }$) reaction at ${\mathit{T}}_{\mathrm{\pi }}$=100 MeV have been made at TRIUMF using a polarized target consisting of 99% ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ enriched butanol. Data were obtained for the ground and 3.68 MeV excited states at angles from 110° to 150° in 10° steps. The data are consistent with zero asymmetry throughout most of this angular range. Uncertainties are typically ±15%, which is sufficient to discriminate among some, but not all, of the currently available theoretical predictions.

Charged particles from protons up to projectile particles were measured from the systems ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$${+}^{51}$V and ${}_{}{}^{15}{}_{}{}^{}\mathrm{N}$${+}^{56}$Fe at 530 MeV bombarding energy forming the same composite ${}_{}{}^{71}{}_{}{}^{}\mathrm{As}_{}^{\mathrm{*}}{}_{}{}^{}$. The data show entrance channel effects with respect to spectral distributions and fragment abundances. The data analysis in terms of different models indicates a common reaction mechanism for all particles produced.

Neutrons have been measured in coincidence with fission fragments of the reaction ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$${(}^{16}$O,f) at bombarding energies ranging between 80 and 130 MeV. Pre-scission and post-scission multiplicities were deduced from the neutron spectra by application of a moving source fit procedure. Particles evaporated before the saddle point configuration of the fissioning nucleus will reduce the nuclear temperature of the transition nucleus. This effect of higher chance fission increases the anisotropies of fission fragment angular distributions compared to the assumption of first chance fission. Compound nuclei with nuclear temperatures considerably smaller than the fission barrier have statistical fission decay times that are much longer than saddle-to-scission times. With these conditions it is plausible that most of the particles evaporated from the fissioning nucleus are emitted before the saddle. Fission fragment angular distributions for ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$${(}^{16}$O,f) analyzed with the transition state model including the nuclear temperature reduction caused by pre-fission particle emission show ‘‘normal’’ anisotropies at low and near barrier energies.

Energetic light ions (primarily protons and alphas) were detected in heavy-ions collisions of ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ with ${}_{}{}^{181}{}_{}{}^{}\mathrm{Ta}$ at an energy E/A=85 MeV. Analysis of the spectral shapes and angular distributions using a standard moving-source model requires that the source velocity approaches the beam velocity at zero degrees. Apparent source temperatures are only modestly increased at this energy compared to apparent source temperatures in reactions at energies E/A=9 to 40 MeV, indicating a possible saturation effect in the projectile nucleus. The production of very energetic light ions (where the light-ion energy approaches the total beam energy) was not seen in this experiment, possibly indicating that a previously proposed massive cluster transfer mechanism is invalid, or suppressed at this higher energy.

We present a new technique for the determination of the reaction plane in heavy-ion reactions at incident energies ranging from the Fermi energy up to ≊100 MeV/nucleon. Our technique exploits the azimuthal correlation between light particles and the reaction plane. For illustrative purposes, azimuthal distributions of particles with respect to the reaction plane are extracted from data taken by the Michigan State University 4π array for 35 MeV/nucleon Ar+V collisions. The influences of momentum conservation and detection biases on the reaction plane determination are discussed, and the accuracy of the new technique is evaluated.

Angular distributions and Q-value spectra for transfer reactions in the systems ${}_{}{}^{36}{}_{}{}^{}\mathrm{S}$${+}^{144,154}$Sm have been measured at two energies close to the Coulomb barrier. Mass and charge identification was achieved using a time-of-flight system followed by an ionization chamber. Transfer probabilities were analyzed considering direct and sequential barrier penetration mechanisms. The dependence of the cross sections on the static quadrupole deformation of the targets was compared with the predictions of a semiclassical approach. The relative yields of the different channels were analyzed in the light of a random-walk approach based on the reaction Q values.

A scheme for including the Coulomb-exchange contribution in momentum-space calculations of proton-nucleus scattering is presented. The main feature of this approach is a careful treatment of the singular two-body Coulomb potential when the Fermi motion of the bound protons is treated explicitly as required by full-folding calculations of microscopic optical potentials. Analytic expressions are presented and applications are discussed.

We use a recently developed microscopic approach to photonuclear reactions at intermediate energies in order to calculate the enhancement κ of the nuclear dipole sum rule over its classical Thomas-Reiche-Kuhn value (60 mb MeV)NZ/A. The difficulties in comparing κ, evaluated with the double commutator, with the observable photonuclear cross section are stressed. However, within this microscopic model it is possible to separate the ingredients that contribute to the magnitude κ and make a qualitative estimate of it. The same model is used to evaluate the empirical κ¯ obtained by integrating the photonulcear cross section up to the pion mass.

Here we introduce a practical approach to optical model phenomenology for heavy ions. The key idea is the determination of a ‘‘spline improved McIntyre’’ S matrix S(l) which is then subjected to S(l)-to-V(r) inversion. We apply this to fitting experimental data for ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ on ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ at 608 MeV and obtain potentials which are significantly different from those found from a simple optimization of McIntyre parameters followed by inversion. In particular we find quite different results for such qualitative features as W/V in the nuclear surface. The potential found is compared with that obtained by conventional analysis. The two-stage procedure has computational advantages for heavy ions.

The concept of the exciton model for nucleon-induced nuclear reactions has been extended to α-induced pre-equilibrium reactions in order to calculate angular distributions and energy spectra of fast ejectile nucleons. The effect of the nucleon motion on the cascade nucleon-nucleon scattering inside the nucleus and the geometrical optical effects at the exit channel are taken into account for the first time in the α-induced pre-equilibrium reaction. Angular distributions of protons from the ${}_{}{}^{165}{}_{}{}^{}\mathrm{Ho}$(α,p) reaction at ${\mathit{E}}_{\mathrm{\alpha }}$=109 MeV were calculated. The observed distributions of the fast protons in the pre-equilibrium region were found to be reproduced well by the calculation.