Excited states in ${}_{}{}^{219}{}_{}{}^{}\mathrm{Ra}$ were studied by means of the ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$${(}^{14}$C, 3n) reaction at 65 MeV. The investigation was made with 12 Compton-suppressed Ge detectors and a multicounter array. Transitions in ${}_{}{}^{219}{}_{}{}^{}\mathrm{Ra}$ were selected by requiring appropriate conditions on fold and sum energy. The proposed level scheme shows two sidebands with alternating parity structure decaying to the ground-state band. It is consistent with a recent description of ${}_{}{}^{219}{}_{}{}^{}\mathrm{Ra}$ in the framework of the reflection-asymmetric mean-field approach, which predicts a K=1/2 ground-state band and two low-lying bands with quantum numbers K=3/2 and K=5/2.

High-spin states in the odd-proton ${}_{}{}^{119,121}{}_{}{}^{}\mathrm{I}$ isotopes have been studied following heavy-ion fusion-evaporation reactions using boron and carbon beams. Both prolate (γ=0°) and oblate (γ=-60°) collective bands have been observed built on low-lying positive- and negative-parity proton states, namely, ${\mathit{h}}_{11/2}$, ${\mathit{g}}_{9/2}$, ${\mathit{g}}_{7/2}$, and ${\mathit{d}}_{5/2}$ orbitals. At the highest spins (∼39/2) the collective behavior of the ${\mathit{h}}_{11/2}$ yrast band is seen to break down when noncollective oblate states become yrast, resulting in the observation of band termination. The terminating state involves the π${\mathit{h}}_{11/2}$⊗[π${\mathit{g}}_{7/2}$${]}^2$⊗[ν${\mathit{h}}_{11/2}$${]}^2$ configuration at γ=+60°.

The mass assignments for the activities previously assigned to ${}_{}{}^{259}{}_{}{}^{}\mathrm{Lr}$ and ${}_{}{}^{258}{}_{}{}^{}\mathrm{Lr}$ have been confirmed. The ${}_{}{}^{259}{}_{}{}^{}\mathrm{Lr}$ and ${}_{}{}^{258}{}_{}{}^{}\mathrm{Lr}$ were produced by the ${}_{}{}^{248}{}_{}{}^{}\mathrm{Cm}$${(}^{15}$N,4n) and ${}_{}{}^{248}{}_{}{}^{}\mathrm{Cm}$${(}^{15}$N,5n) reactions, respectively. The Lr α activities were measured directly using our rotating wheel system. Mass assignments were made by an α-daughter recoil catcher technique in which the ${}_{}{}^{255}{}_{}{}^{}\mathrm{Md}$ and ${}_{}{}^{254}{}_{}{}^{}\mathrm{Md}$ daughters were caught on aluminum foils placed directly above the rotating wheel. The α decay of the 20.07-h ${}_{}{}^{255}{}_{}{}^{}\mathrm{Fm}$ and the 3.24-h ${}_{}{}^{254}{}_{}{}^{}\mathrm{Fm}$ granddaughter activities in these aluminum foils were then measured and correlations with the decay of the Lr parent activities were made based on the distribution of the Fm activities among the Al foils, which corresponded to the half-lives of the parent Lr α activities. We have determined the half-lives for ${}_{}{}^{259}{}_{}{}^{}\mathrm{Lr}$ and ${}_{}{}^{258}{}_{}{}^{}\mathrm{Lr}$ to be 6.${34}_{\mathrm{-}0.42}^{+0.46\mathrm{}}$ and 3.${92}_{\mathrm{-}0.31}^{+0.35\mathrm{}}$ s, respectively. The spontaneous-fission branch in ${}_{}{}^{259}{}_{}{}^{}\mathrm{Lr}$ was measured to be 23±2%. The spontaneous-fission mass distribution appears to be broadly symmetric and the average total kinetic energy is estimated to be 200±10 MeV.

A new nuclide ${}_{}{}^{263}{}_{}{}^{}\mathrm{Ha}$ was produced in the bombardment of a ${}_{}{}^{249}{}_{}{}^{}\mathrm{Bk}$ target with 93-MeV ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$ ions. It was detected via spontaneous fission counting and was shown to have a half-life of about 0.5 min. This activity was also separated from the reaction products by automated rapid chemical separations using cation-exchange chromatography in 0.05M α-hydroxyisobutyric acid. After chemical separation, ${}_{}{}^{263}{}_{}{}^{}\mathrm{Ha}$ was found to decay by spontaneous fission (${57}_{\mathrm{-}15}^{+13\mathrm{}}$%) and by α emission (${\mathit{E}}_{\mathrm{\alpha }}$=8.35 MeV, 43%) with a half-life of ${27}_{\mathrm{-}7}^{+10\mathrm{}}$ s. The spontaneous fission fragment energy spectrum is compatible with an average total kinetic energy of about 200 MeV.

We have measured the probability of double K-shell vacancy production in the electron capture decay of ${}_{}{}^{125}{}_{}{}^{}\mathrm{I}$ to the 35-keV level of ${}_{}{}^{125}{}_{}{}^{}\mathrm{Te}$. The probability was deduced from the number of triple coincidences between the Te hypersatellite and satellite x rays produced in filling the double vacancy, and the subsequent normal x ray accompanying the K internal conversion of the 35-keV level. The probability of double K-shell vacancy production per K-shell electron capture (${\mathit{P}}_{\mathit{K}\mathit{K}}$) was found to be (1.35±0.15)×${10}^{\mathrm{-}5}$.

We calculate level densities for ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$, ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$, and ${}_{}{}^{100}{}_{}{}^{}\mathrm{Ru}$ nuclei using unrestricted uniform, single particle levels (Fermi gas) and for realistic levels restricted to those bound by centripetal and Coulomb forces. For the latter we use single particle levels due to Seeger, and results for a Woods-Saxon model. We show that the Fermi gas formulas become completely inadequate at temperatures well within the range of those relevant to heavy-ion reaction studies. We discuss likely consequences of these discrepancies with respect to the likelihood of forming equilibrated nuclei at these temperatures, and discuss possible pitfalls of interpreting reactions at high excitations using unrestricted Fermi gas formulas.

The variational extreme condition with respect to statistical distribution of nucleons in momentum space is applied to derive the Euler equation of the nuclear density profile. The resultant Euler equation of the nuclear density profile is proven to be identical with that obtained in the usual Thomas-Fermi theories of a hot nuclear system where the variation is made with respect to the nuclear density profile. A Fermi-Dirac-type distribution appears as a result of variation in the present approach, while it is used as a given expression in obtaining the variation of the nuclear density profile in the usual Thomas-Fermi theories.

We examine the random phase approximation (RPA) based on a relativistic Hartree approximation description for nuclear ground states. This model includes contributions from the negative energy sea at the one-loop level. We emphasize consistency between the treatment of the ground state and the RPA. This consistency is important in the description of low-lying collective levels but less important for the longitudinal (e,e’) quasielastic response. We also study the effect of imposing a three-momentum cutoff on negative energy sea contributions. A cutoff of twice the nucleon mass improves agreement with observed spin-orbit splittings in nuclei compared to the standard infinite cutoff results, an effect traceable to the fact that imposing the cutoff reduces ${\mathit{m}}^{\mathrm{*}}$/m. Consistency is much more important than the cutoff in the description of low-lying collective levels. The cutoff model also provides excellent agreement with quasielastic (e,e’) data.

We have reanalyzed the (e,e’) and (p,p’) data at 318 MeV on the stretched, ${12}_{1,2}^{\mathrm{-}}$ and ${14}^{\mathrm{-}}$, states of ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ using the ideas of G. Brown and co-workers on the reduction of meson and nucleon masses in the nuclear medium. The reaction calculations are compared with new, large basis random-phase-approximation calculations using a residual interaction, also modified, in a consistent way. The resulting interaction, based on the one boson exchange (π+ρ) model, has reduced tensor and enhanced spin-orbit strengths. Agreement between electron and proton quenching factors is found for effective masses, ${\mathit{m}}^{\mathrm{*}}$/m≃0.79–0.86. The reduction or enhancement factors for the modified interaction are in qualitative agreement with those found in other analyses.

Nuclear structure aspects of the double-charge-exchange (DCX) reaction on nuclei are studied. Using a variety of DCX-type two-body transition operators, we explore the influence of two-body correlations among valence nucleons on the DCX transition amplitudes to the isobaric analog state and to other nonanalog ${\mathit{J}}^{\mathrm{\pi }}$=$0^{+}$ states. In particular, the question of the spin dependence and of the range of the DCX transition operators is explored and the behavior of the transition amplitudes as a function of the valence nucleon number is studied. It is shown that the two-amplitude DCX formula derived by Auerbach, Gibbs, and Piasetzky for a single ${\mathit{j}}^{\mathit{n}}$ configuration holds also in some cases when configuration mixing is strong. DCX-type transitions from the Ca and Ni isotopes to the Ti and Zn isotopes and from ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}$ to ${}_{}{}^{56}{}_{}{}^{}\mathrm{Ni}$ are the subject of this study.

The modified finite-temperature random phase approximation (FT-RPA) has been constructed by taking the influence of thermostat on the structure of quasiparticles into account. The modified FT-RPA linear response for electric quadrupole (${\lambda }^{\mathrm{\pi }}$=$2^{+}$) and octupole (${\lambda }^{\mathrm{\pi }}$=$3^{\mathrm{-}}$) excitations in ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$ has been calculated as a function of the nuclear temperature. As compared to the conventional FT-RPA, the modified FT-RPA has given a stronger spreading for the strength distribution of quadrupole excitations at finite temperature T≤3 MeV.

A new microscopic nuclear mass formula is derived from the fermion dynamical symmetry model. A Strutinsky-like spherical single-particle shell correction is introduced, but the principle part of the pairing and deformation are treated microscopically through the pairing and quadrupole-quadrupole two-body interaction, without introducing a deformed mean-field or BCS approximation. The results are in excellent agreement with existing mass data in the actinide region and suggest the possibility of a new region of superheavy elements near Z=114 and N=164. This mass formula has been utilized in the study of r processes in astrophysical problems with encouraging preliminary results.

Calculations have been performed to explore the effect of configuration mixing in a large basis on the fragmentation of ‘‘stretched’’ M6 strength in the sd-shell nuclei ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$, ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$, ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$, ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$, and ${}_{}{}^{36}{}_{}{}^{}\mathrm{Ar}$. This work elaborates on results for ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ given previously, extends those calculations to neighboring N=Z nuclei with the same basis restriction (one particle in the 1${\mathit{f}}_{7/2}$ orbit and up to four particles in the 1${\mathit{d}}_{3/2}$ orbit) used in that earlier paper, and examines all self-conjugate sd-shell nuclei in a basis with one particle in the 1${\mathit{f}}_{7/2}$ orbit and unrestricted occupancy of the sd-shell orbits. It is found that configuration mixing in a large basis reproduces interesting features of the spectrum for ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ and ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$ and gives an improved description of other properties of the observed $6^{\mathrm{-}}$ states, but fails to describe the observed spectrum in ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$. Emphasis is placed on the location of additional observable fragments of the M6 response.

We examine a variational approximation for the ground state of a quantum system, based on a specially defined quantal entropy, within the context of two different nuclear models dealing with pairing and monopole interactions. A substantial improvement over standard and projected Hartree-Fock and BCS descriptions is obtained, especially in transitional regions and in the description of fluctuations of relevant quantities. An analytic treatment is also developed for the thermodynamic limit.

Excitation functions of isomeric yields have been measured for ${}_{}{}^{198}{}_{}{}^{}\mathrm{Tl}$, ${}_{}{}^{197}{}_{}{}^{}\mathrm{Hg}$, ${}_{}{}^{198}{}_{}{}^{}\mathrm{Au}$, and ${}_{}{}^{196}{}_{}{}^{}\mathrm{Au}$ produced by α${+}^{197}$Au reactions in the 35–50 MeV energy range. The isomeric yield ratios are analyzed in terms of pre-equilibrium and evaporation emissions. Single as well as two-nucleon pre-equilibrium emissions are taken into account. Various combinations of pre-equilibrium and equilibrium emissions together with different sequences in which the ejectiles may be emitted are explicitly considered to evaluate the average spin distribution of the final nucleus. The choice of the spin cutoff parameter and the effect of forward-angle emissions of pre-equilibrium particles have been investigated. The isomeric yield ratios are found to depend sensitively on the pre-equilibrium angular distribution and on the spin cutoff parameter for equilibrium emissions. Inadequate description of the reaction mechanism leads to incorrect predictions of excitation functions as well as isomeric yield ratios.

The ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$${+}^{12}$C reaction at an incident energy E/A of 38 MeV has been investigated experimentally. Singles energy spectra and the angular distribution of reaction residues having 3≤Z≤9 were measured. A small low-energy cutoff in the spectra combined with measurements at large angles (up to 70°) allowed a study of the systematics involved in the production of low-energy reaction residues. A target-related origin is proposed for these yields. Cascade model calculations are presented which support this hypothesis.

Radiochemical activation techniques were used to study the behavior of projectile fragments formed in the interaction of 44 GeV ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ ions within thick Cu targets. After a short review of the results obtained hitherto with this Cu-target technique, the interaction of 44 GeV ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ with several copper target configurations yielding the deep spallation product ${}_{}{}^{24}{}_{}{}^{}\mathrm{Na}$ is described. Energetic fragments which are emitted into the laboratory angles 10°≤θ≤45° appear to produce more ${}_{}{}^{24}{}_{}{}^{}\mathrm{Na}$ (up to nearly one order of magnitude) than calculated with a phenomenological model and an intranuclear cascade model. This enhanced production of ${}_{}{}^{24}{}_{}{}^{}\mathrm{Na}$ by wide-angle secondaries is only observed for 44 GeV ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ on copper, but not for 25 GeV ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ on copper. Some normalization experiments with 4 GeV ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ and 2.6 GeV p are described.

Systematic results are presented for multiplicity distributions of ${}_{}{}^{1,2,3}{}_{}{}^{}\mathrm{H}$ and ${}_{}{}^{3,4,6,8}{}_{}{}^{}\mathrm{He}$ produced in reactions of ${}_{}{}^{\mathrm{nat}}{}_{}{}^{}\mathrm{Ag}$ with ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$ beams of 280, 680, 1080, and 1356 MeV. A variety of gating conditions is explored and classified in connection with the more peripheral or the more central collisions. Correlations between H-He multiplicity and Z or angle of projectilelike fragments follow qualitative expectations for deeply inelastic scattering. Pairs of light charged particles or intermediate-mass fragments at side angles are well correlated with the most violent collisions, leading to incomplete fusion. The cross sections for these more central collisions imply entrance-channel orbital angular momenta up to ≊300ħ in the reactions that form very highly excited composite nuclear systems.

Differential cross sections for the ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$(p,n${)}^{14}$N reaction were measured at ${\mathit{E}}_{\mathit{p}}$=35 MeV. A number of spin-isospin excitations have been observed including Gamow-Teller-type $0^{+}$→$1^{+}$ and 0ħω and 1ħω jump stretched transitions. Distorted-wave Born-approximation calculations using shell-model wave functions have successfully reproduced the experimental results. Renormalization factors of about 0.5 were required for the spin-flip transitions leading to the 3.947-MeV $1^{+}$ state and to the 7.026-MeV $2^{+}$ state, where ΔJ(ΔL,ΔS)=1(0,1) and 2(2,1), respectively. Proton and neutron optical-potential parameters were derived in the course of the present work.

Pre-scission and post-scission neutron yields have been measured as a function of projectile mass, compound nucleus fissility, and fission mass split and total kinetic energy (TKE) for 27 fusion-fission and quasifission reactions induced by beams of ${}_{}{}^{16,18}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$, and ${}_{}{}^{64}{}_{}{}^{}\mathrm{Ni}$. A new method of interpretation of experimental pre-scission neutron multiplicities ${\nu }_{\mathrm{pre}}$ and mean kinetic energies ${\mathrm{\varepsilon }}_{\nu }$ allows the extraction of fission time scales with much less uncertainty than previously, all fusion-fission results being consistent with a dynamical time scale of (35±15)×${10}^{\mathrm{-}21}$ s for symmetric fission. All reactions show that ${\nu }_{\mathrm{pre}}$ falls quite rapidly with increasing mass asymmetry; evidence is presented that for fusion-fission reactions this is partly due to a reduction of the dynamical fission time scale with mass asymmetry. For quasifission, the data indicate that the pre-scission multiplicity and mean neutron kinetic energy are very sensitive to the final mass asymmetry, but that the time scale is virtually independent of mass asymmetry. It is concluded that for fusion-fission there is no dependence of ${\nu }_{\mathrm{pre}}$ on TKE, while for ${}_{}{}^{64}{}_{}{}^{}\mathrm{induced}$ quasifission reactions, a strong increase of ${\nu }_{\mathrm{pre}}$ with decreasing TKE is observed. This is probably largely caused by neutron emission during the acceleration time of the fission fragments in these fast reactions. Interpretation of post-scission multiplicities in terms of fragment excitation energies leads to deduced time scales consistent with those determined from the pre-scission data.