The minimal-energy solution of the SU(2) Skyrme model with baryon number three is a soliton with tetrahedral symmetry 4¯3m. Given one assumption, I show how this symmetry ensures that the ${\mathit{J}}^{\mathrm{\pi }}$=1/$2^{+}$ isodoublet nucleus ${(}^3$He${,}^3$H) emerges as the unique ground state of this soliton solution when its isospin and rotational zero modes are quantized.

Measurements of the spin dependence of n-p elastic scatteing at ${\mathit{E}}_{\mathit{n}}$=183 MeV have been carried out with polarized neutrons and polarized protons. If charge symmetry holds, the two analyzing powers ${\mathit{A}}_{\mathit{n}}$ and ${\mathit{A}}_{\mathit{p}}$ must be equal. The measured value of ΔA==${\mathit{A}}_{\mathit{n}}$-${\mathit{A}}_{\mathit{p}}$, averaged over the angular range 82.2°≤${\mathrm{\theta }}_{\mathrm{c}.\mathrm{m}.\mathrm{}}$≤116.1°, is (33.1±5.9±4.3)×${10}^{\mathrm{-}4}$. This result represents clear evidence of charge-symmetry violation in the strong interaction. The measurement agrees well with predictions from meson-exchange theory when these include the isospin mixing of the ${\mathrm{\rho }}^0$ and ${\mathrm{\omega }}^0$ mesons.

Partial cross sections of evaporation residues following the fusion reactions ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$${+}^{68}$Zn, ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$${+}^{64}$Ni, and ${}_{}{}^{37}{}_{}{}^{}\mathrm{Cl}$${+}^{59}$Co have been measured for center-of-mass energies from 5 MeV below to 10 MeV above the Coulomb barrier. Average angular momentum l¯ has been deduced from these cross sections on the basis of statistical-model calculations. These are compared to l¯ values that can be derived from the shape of the measured excitation function of these reactions, on the basis of some simple assumptions. Good agreement is found between these two, establishing the validity of these assumptions.

Exchange currents in nuclei are derived from chiral Lagrangians, and a justification is offered for the ‘‘chiral filter hypothesis’’ which seems to be supported by all presently available experimental data.

Cross sections, pion momentum spectra, and angular distributions for the reactions ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(${\mathrm{\pi }}^{\mathrm{-}}$,${\mathrm{\pi }}^{+}$${\mathrm{\pi }}^{\mathrm{-}}$) and ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(${\mathrm{\pi }}^{\mathrm{-}}$,2${\mathrm{\pi }}^{\mathrm{-}}$) at a bombarding energy of 292 MeV were measured wth a 360° spectrometer. An enhancement of the cross-section ratio of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(${\mathrm{\pi }}^{\mathrm{-}}$,2${\mathrm{\pi }}^{\mathrm{-}}$) to ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(${\mathrm{\pi }}^{\mathrm{-}}$,${\mathrm{\pi }}^{+}$${\mathrm{\pi }}^{\mathrm{-}}$) relative to that of the elementary cross sections was observed, and is discussed in terms of various nuclear-medium effects including a double-Δ production channel.

Inclusive electron-scattering cross sections have been measured for ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}$ in the quasielastic region at electron energies between 0.9 and 4.3 GeV, at scattering angles of 15° and 85°. Longitudinal and transverse response functions at a q of 1.14 GeV/c have been extracted using a Rosenbluth separation. The experimental Coulomb sum has been obtained with aid of an extrapolation. The longitudinal response function, after correction for Coulomb distortion, is lower than quasifree-scattering-model predictions at the quasielastic peak and on the high-ω side.

The cross section of the isovector giant dipole resonance (GDR) excited by inelastic scattering of 120-MeV α particles for 0°≤Θα’≤3° has been measured using the ${}_{}{}^{116,124}{}_{}{}^{}\mathrm{Sn}$(α,α’${\gamma }_0$) and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$(α,α’${\gamma }_0$) reactions. The results are compared with distorted-wave Born-approximation calculations with a GDR form factor depending on the relative difference of proton and neutron radii (Δ${\mathit{R}}_{\mathit{p}\mathit{n}}$/${\mathit{R}}_0$). Within the model used, the Δ${\mathit{R}}_{\mathit{p}\mathit{n}}$/${\mathit{R}}_0$ values for ${}_{}{}^{116}{}_{}{}^{}\mathrm{Sn}$, ${}_{}{}^{124}{}_{}{}^{}\mathrm{Sn}$, and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ deduced from the comparison of measured and calculated cross sections are (0.$7_{\mathrm{-}0.7}^{+2.3\mathrm{}}$)%, (4.$1_{\mathrm{-}2.5}^{+2.1\mathrm{}}$)%, and (3.0±1.3)%, respectively.

Nuclei with Z up to 82 emitted in the ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$${+}^{197}$Au reaction at ${\mathit{E}}_{\mathrm{lab}}$=29 MeV per nucleon have been measured as a function of the associated neutron multiplicity. The data reveal the presence of strong correlations between character of a collision and neutron multiplicity. The trends suggest a disassembly of the nuclear system into a large number of nucleons and small fragments in the events with the highest neutron multiplicity. In such events, approximately one-third of the neturons are released from the system and fragment yields decrease in an exponential fashion with increasing mass.

It is shown that the nuclear Hamiltonian scrH separates rigorously into a monopole field ${\mathit{scrH}}_{\mathit{m}}$ and a multipole part ${\mathit{scrH}}_{\mathit{m}}$. ${\mathit{scrH}}_{\mathit{m}}$ is entirely responsible for saturation properties and can be treated phenomenologically with few parameters. When realistic interactions are used for ${\mathit{scrH}}_{\mathit{M}}$ in regions from the p shell to the N=82 isotones, shell-model calculations yield excellent spectroscopy and demand nuclear radii very close to the observed ones.

Quasistatic field configurations are computed for the two-Skyrmion system with large separation. The total energy obtained is much lower than that for the product approximation. In particular, the repulsion in the two-pion range is considerably reduced.

An accurate particle-number-conserving calculation shows that in a single-j (j=13/2) model the yrast-yrare interaction V is always strong and no periodic oscillation of V with Fermi energy λ is obtained. However, in a two-j model or realistic nuclei sharp backcrossings do occur for appropriate single-particle level distribution and oscillation of V with increasing λ is found. The occupation-number distribution for the high-j shell plays a key role in understanding the backcrossing properties.

Measurements are reported of orientation asymmetries in the forward-angle differential cross sections for pion single-charge-exchange scattering of aligned and unaligned ${}_{}{}^{165}{}_{}{}^{}\mathrm{Ho}$ nuclei. The extrapolated 0° asymmetry of -0.022±0.024 indicates a quadrupole deformation ratio ${\mathrm{\beta }}_2^{\mathit{a}}$/${\mathrm{\beta }}_2^{\mathit{c}}$=0.84±0.08. This result conflicts with the predictions of the best available Hartree-Fock models.

Four new superdeformed bands have been observed in ${}_{}{}^{194}{}_{}{}^{}\mathrm{Tl}$, in addition to the two already reported. These six bands consist of three signature-partner pairs, whose energies and spacings closely resemble those in the two superdeformed bands recently reported in ${}_{}{}^{193}{}_{}{}^{}\mathrm{Tl}$. The transition-energy similarities and angular momentum alignments of these bands are discussed.

The concept of resonant tunneling is invoked to explain the sharp drop in the measured spontaneous-fission half-life when going from ${}_{}{}^{256}{}_{}{}^{}\mathrm{Fm}$ to ${}_{}{}^{258}{}_{}{}^{}\mathrm{Fm}$. Various consequences of such a suggestion on the other observed characteristics of the bimodal symmetric fission of ${}_{}{}^{258}{}_{}{}^{}\mathrm{Fm}$ are briefly discussed.

A microscopic model for estimating ${\mathit{n}}_0$, the initial number of degrees of freedom used in calculating pre-equilibrium nucleon emission from heavy-ion reactions, is presented. The model follows the evolution of the geometrical and phase spaces during the process of the gradual fusioning of the target and the projectile. A good agreement is found between the calculated values of ${\mathit{n}}_0$ and the empirical values extracted from fits to nucleon spectra.

High-energy photon and neutron emission has been measured in coincidence with fission fragments in α${+}^{232}$ Th reactions at 170 MeV. From measurements parallel and perpendicular to the fission plane, anisotropies relative to the reaction plane were determined. The in-plane/out-of-plane intensity ratio is 0.72(7) for photons with energies above 20 MeV and 11(3) for neutrons at 35 MeV. The result for high-energy photons can be explained by nucleon-nucleon bremsstrahlung if the initial flow of nucleons has a correlation to the reaction plane similar to the one observed for fast neutrons.

Using parity projection and the generator-coordinate method we investigate the left-right-asymmetric softness of the superdeformed minimum of ${}_{}{}^{194}{}_{}{}^{}\mathrm{Pb}$. The collective wave functions exhibit large octupole dipsersions. Our calculation suggests that above the ground-state superdeformed band there should exist a negative-parity band of similar quadrupole deformation with an excitation energy close to 2 MeV.

For the first time, definite evidence for the existence of two-phonon collective states in deformed nuclei has been established through the measurement of the absolute transition rate for the decay of the double-γ ${\mathit{K}}^{\mathrm{\pi }}$=$4^{+}$ vibration in ${}_{}{}^{168}{}_{}{}^{}\mathrm{Er}$.

We examine the deuteron properties using the new value for the πNN coupling constant, ${\mathit{g}}_{\mathrm{\pi }}^2$/4π=13.3±0.3, which has been obtained in a recent analysis of ${\mathrm{\pi }}^{\pm }$p data and is about 7% smaller than earlier determinations. We find that this value is at variance with the deuteron properties if the strong empirical (Höhler-Pietarinen) ρ coupling is assumed which, in fact, is used in almost all modern realistic meson-theoretic models for the NN interaction. Within such models, a minimum of 13.9 for ${\mathit{g}}_{\mathrm{\pi }}^2$/4π is required, especially for the correct description of the deuteron quadrupole moment.

Absolute total and differential cross sections for the reaction ${\mathrm{\pi }}^{+}$+d→p+p have been measured for pion energies from 3.7 to 20.5 MeV. Evidence for p-wave strength was observed for all energies. Using detailed balance and corrections for Coulomb effects, the measured differential and total cross sections were found to be consistent with recent measurements for the reaction n+p→d+${\mathrm{\pi }}^0$, offering no evidence for charge-independence breaking. The measured total cross sections for energies below 30 MeV are in disagreement with predictions by Blankleider and by Vogelzang, Bakker, and Boersma.