Inelastic scattering of 129 MeV alpha particles has been used to excite the giant quadrupole resonance in ${}_{}{}^{58,60,62,64}{}_{}{}^{}\mathrm{Ni}$. The resonance was found to exhaust 58±12 %, 76±14 %, 78±14 %, and 90±16 % of the E2 energy-weighted sum rule, respectively, for ${}_{}{}^{58,60,62,64}{}_{}{}^{}\mathrm{Ni}$.

Several collective structures have been populated in the Z=55 nucleus ${}_{}{}^{123}{}_{}{}^{}\mathrm{Cs}$ following the ${}_{}{}^{108}{}_{}{}^{}\mathrm{Pd}$${(}^{19}$F,4n) fusion-evaporation reaction at a beam energy of 76 MeV. The low-lying structure is found to be dominated by a decoupled rotational band built on the unique-parity π${\mathit{h}}_{11/2}$ orbital. Rotational structures based on the normal-parity ${\mathit{g}}_{7/2}$ proton and the ${\mathit{g}}_{9/2}$ proton-hole orbitals are also observed. Rotational alignments occur in the π${\mathit{h}}_{11/2}$ band at ħ${\mathrm{\omega }}_{\mathit{c}}$≊0.44 MeV, and in the π${\mathit{g}}_{9/2}^{\mathrm{-}1}$ band at ħ${\mathrm{\omega }}_{\mathit{c}}$=0.38 MeV, both attributed to the rotational alignment of a pair of ${\mathit{h}}_{11/2}$ neutrons, despite the different crossing frequency. In addition, the γ-vibrational band built on the π${\mathit{h}}_{11/2}$ orbital has been observed feeding both signatures of the corresponding rotational cascade. These results are compared to cranked shell model calculations and to the systematics of the region.

We have used the finite-range, rotating-liquid-drop model to calculate the conditional saddle-point shapes, fission barriers, and moments of inertia of the nucleus ${}_{}{}^{149}{}_{}{}^{}\mathrm{Tb}$ as functions of mass asymmetry (or fragment charge Z) and angular momentum. A strong motivation in the present work is the potentiality for predicting total kinetic energies (TKE) in asymmetric fission, which may be compared with measurements of intermediate-mass fragments (IMF’s) produced in heavy-ion reactions. From the conditional saddle points, we estimate the TKE in the limit of no post-saddle dissipation, yielding, in effect, upper limits for the TKE’s. Clearly the nuclear shapes at scission will produce lower limits for the TKE’s, and we propose two methods for determining the characteristics of such scission configurations. The first involves a linear extrapolation along the fission normal mode at the conditional saddle point, and the second employs Swiatecki’s scaling rule to determine the effect of dissipation on the nuclear elongation at scission. In comparison to experimental TKE results for IMF’s, corrected for light particle evaporation, we find that the predictions from saddle-point shapes are in rather good agreement with the data over a wide range of mass asymmetry. The calculated estimates from nondissipative scission-point configurations also agree fairly well with the data, but tend to underpredict the TKE’s significantly for the heavier IMF’s. This is not a serious concern, as the calculations have not included any prescission damping. The estimates from fully dissipative scission-point shapes are systematically low, falling appreciably below the data over the whole range studied. Within the confines of the present asymmetric fission model, we can conclude that the motion along the dissipative path is not completely damped, and that asymmetric fission appears to be a less dissipative process than symmetric fission.

A classical microscopic theory of mixed states has recently been formulated in order to deal with the theoretical description of nuclear phenomena observed in highly excited states. In this theory, which is here briefly reviewed, the degrees of freedom of real fermions are doubled by fictitious fermions, in the context of the formalism of thermofield dynamics. The requirement of static stability of the thermal state of equilibrium plays, in the theory, a relevant role. The possibility of constraining the dynamics of the fictitious degrees of freedom, in such a way as to eliminate spurious thermal excitations, is discussed. The concept of canonical collective variables for mixed states is analyzed. Boson expansions appropriate to describe collective excitations of hot quantal systems are introduced and their properties investigated. It is shown that thermal boson expansions based on the formalism of thermofield dynamics are free from formal inconsistencies which may be present in boson expansions derived by an ad hoc quantization of conventional thermal mean field theories. The formalism is applied to the Lipkin model, and the correlation energy of a hot system is discussed.

A new method for constructing periodic orbits of the time-dependent Hartree-Fock equations is proposed. It is based on a perturbative expansion in the amplitude of the collective vibration. We present applications to the case of octupole vibrations in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ and ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$. From calculations performed up to second order we determine the splitting of the two-phonon states. We discuss the problems which, for the quadrupole mode, arise from a resonant coupling of the vibration with states of the continuum.

The temperature dependence of the different thermodynamic quantities like entropy, equation of state, free energy, internal energy, effective mass, chemical potential, etc. are calculated for nuclear and neutron matter within a fully self-consistent model and compared with the results obtained by others. An effective interaction consisting of Sussex interaction plus an empirical density-dependent interaction is taken in the calculation. The latter is added so as to correctly reproduce the saturation property of nuclear matter. The calculated entropy is in excellent agreement with experiment.

The shapes of rotating Xe, Ba, Ce, Nd, and Sm nuclei (84≤N≤94) are calculated using the cranking model with the Woods-Saxon average potential and pairing. The lightest isotopes of Xe and Ba have nearly spherical ground states, but develop octupole and quadrupole deformations under rotation which remain up to very high spins. The ground states of the heavier isotopes have octupole and quadrupole deformations which persist up to medium spins (I≊12ħ). At higher spins, a shape transition is predicted to reflection-symmetric aligned many-quasiparticle configurations.

Successful spectroscopic calculations for the $0_1^{+}$, $2_1^{+}$, and $4_1^{+}$ levels in ${}_{}{}^{146\mathrm{-}158}{}_{}{}^{}\mathrm{Sm}$ are carried out in sdg boson space with the restriction that the s-boson number ${\mathit{n}}_{\mathit{s}}$≥2 and the g-boson number ${\mathit{n}}_{\mathit{g}}$≤2. Observed energies, quadrupole and magnetic moments, E2 and E4 transition strengths, nuclear radii, and two-nucleon transfer intensities are reproduced with a simple two-parameter Hamiltonian. For a good simultaneous description of ground, β, and γ bands, a Hamiltonian interpolating the dynamical symmetries in the sdg model is employed. Using the resulting wave functions, in ${}_{}{}^{152,154}{}_{}{}^{}\mathrm{Sm}$, the observed B(E4;$0_1^{+}$→$4_{\gamma }^{+}$) values are well reproduced and E4 strength distributions are predicted. Moreover, a particular ratio scrR involving two-nucleon transfer strengths showing a peak at neutron number 90 is well described by the calculations.

We have previously used a cluster model, employing a square-well nuclear potential plus a surface-charge Coulomb potential, to satisfactorily describe α-decay half-lives for more than 400 nuclei. Here, we investigate a more realistic version of this cluster model, in which the square-well nuclear potential is replaced by a ‘‘cosh’’ potential geometry having nonzero diffuseness, and the Coulomb potential by one appropriate to a point charge α particle interacting with a uniformly charged spherical core. By varying the adjustable parameters of this more realistic model, we find several potentials which give comparable fits to the α-decay data, and select the one which best tallies with information from other areas of nuclear physics. In addition, we find that the α-particle preformation probability needed to describe favored transitions in odd-mass nuclei is only 60% of the equivalent quantity required for the ground state to ground state transitions of even-even nuclei.

The distribution of isoscalar monopole strength is calculated in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ and ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ using the Dirac-Hartree random phase approximation. The resulting strength has a wide distribution and the average energy is lower than one would expect from the high compressibility coefficient in nuclear matter inherent in the relativistic theories. The distribution of the monopole strength has several peaks but only the highest peak in ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ can reliably be related to the ‘‘breathing’’ mode and thus to the nuclear compressibility.

A correlated finite-temperature Hartree-Fock (FTHF) approximation is examined in a three-level U(3) fermion model and compared with conventional FTHF and exact canonical results. It is seen that the correlated treatment is able to yield a more reliable picture of the thermal behavior for a finite number of particles, which may differ substantially from that given by conventional FTHF.

It is shown that the presence of pre-formed α-like structures induces deformations in both light and heavy nuclei.

Coincidences between inelastically scattered α particles and fission products from ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ have been measured with a 172 MeV α beam. Inelastically scattered α particles were measured at angles between 0° and 4°. The fission decay of the giant resonances, in particular, of the giant quadrupole resonance, is clearly observed in the coincidence data. Experimental fission probabilities are well described within the statistical model. The multipole strength, extracted from the angular distribution, is consistent with that obtained from singles (α,α’) measurements if a background due to multistep processes is taken into account.

Elastic scattering and quasielastic transfer yields have been measured for ${}_{}{}^{76,82}{}_{}{}^{}\mathrm{Se}$${+}^{192,198}$Pt using ${}_{}{}^{76}{}_{}{}^{}\mathrm{Se}$ and ${}_{}{}^{82}{}_{}{}^{}\mathrm{Se}$ beams with laboratory energies of 487.7 and 499.0 MeV, respectively. The variation of the one-neutron transfer yields as function of projectile and target mass can be understood on the basis of Q matching. Quasielastic transfer contributes at most 30% to the total reaction cross section with the remainder probably accounted for by deep-inelastic scattering.

Differential cross sections for electron scattering from ${}_{}{}^{140}{}_{}{}^{}\mathrm{Ce}$ have been measured for excitation energies less than 3.3 MeV over a range of effective momentum transfer of 0.4 to 3.1 ${\mathrm{fm}}^{\mathrm{-}1}$. The data have been analyzed to extract transition charge densities. These densities are interpreted in terms of a quasiparticle-phonon model and self-consistent finite Fermi system theory to disentangle the collective and noncollective modes of excitation.

Excitation functions have been measured for complex fragments with atomic number Z=3–15 emitted in collisions of E/A=20–100 MeV ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ ions with targets of ${}_{}{}^{\mathrm{nat}}{}_{}{}^{}\mathrm{Ag}$ and ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$. The results are analyzed in terms of a three-source model which includes: projectilelike fragments from peripheral processes, nonequilibrium emission, and statistical decay of fully equilibrated compound nuclei. Nonequilibrium emission of complex fragments is found to increase rapidly relative to equilibrium emission up to E/A≊60 MeV and then remain approximately constant thereafter. Evidence for enhanced production of heavier intermediate-mass fragments is found in the data for reactions with the ${}_{}{}^{\mathrm{nat}}{}_{}{}^{}\mathrm{Ag}$ target at energies above E/A≊60 MeV. Fit parameters for the equilibrium and nonequilibrium sources are examined. In particular, it is observed that the temperature parameter for nonequilibrium emission of complex fragments is independent of bombarding energy up to E/A=100 MeV.

To provide an accurately calibrated polarization analyzer, the analyzing power for elastic scattering of protons from natural carbon at ${\mathit{E}}_{\mathrm{lab}}$=50.24 MeV and ${\mathrm{\theta }}_{\mathrm{lab}}$=50.0° was measured by scattering protons of very high and precisely known polarization (0.9965±0.0007) from a graphite target. The result of the calibration is A=0.9277±0.0036, where the error is the quadratic sum of the statistical error ±0.0033 and systematic uncertainties which total ±0.0016.

Absolute cross sections for the ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$(α,2α${)}^3$H reaction, measured at 77, 99, and 119 MeV, show features expected for α-α quasielastic scattering from α clusters bound in an l=1 state: minima and maxima for triton momenta of 0 and 55±4 MeV/c, respectively. The magnitudes and energy dependence of the cross sections, and the most probable spectator momenta, were reproduced with distorted-wave impulse approximation calculations when the volume integrals of the optical-model central potentials and ground-state interactions were adjusted to currently accepted values.

Measurements of neutron yields and their angular distributions in coincidence with fission fragments produced in antiproton annihilation at rest in a natural uranium target have been carried out Low Energy Antiproton Ring (LEAR) at CERN. A total of 16.3±0.9 neutrons per annihilation have been found, distributed among direct knockout (27%), evaporation (21%), and fission (52%) processes. Angular distributions show that neutrons below approximately 5 MeV result entirely from moving fission fragments, and above approximately 12 MeV entirely from the excited, prescission nucleus. An estimate of the angular momentum of the excited fission fragment gives ∼13ħ. We are able to account for all baryons produced in annihilation, including neutrons from this experiment and light charged nuclei found in another LEAR experiment, to within 4.5±2.5 of the initial 237 units in the initial state.

The excitation function of (α,xn) reactions on ${}_{}{}^{191}{}_{}{}^{}\mathrm{Ir}$ (abundance 37.3%) and on ${}_{}{}^{193}{}_{}{}^{}\mathrm{Ir}$ (abundance 62.7%) has been measured for the 17–55 MeV alpha-particle bombarding energy range. The stacked foil activation technique and γ-ray spectroscopy were used to determine the cross sections. The experimental data were compared with calculated values obtained by means of a geometry-dependent hybrid model. The initial exciton number ${\mathit{n}}_0$=4 with n=2, p=2, and h=0 gives the best agreements with the presently measured results. To calculate the excitation function theoretically a computer code was used. This set of excitation functions provides a data basis for probing the validity of combined equilibrium and preequilibrium reaction models in a considerable energy range.