Emulsion chambers were used to measure the transverse momenta of photons or ${\pi }^0$ mesons produced in high-energy (≥1 TeV/amu) cosmic-ray nucleus-nucleus collisions. A group of events having large average transverse momenta have been found which apparently exceed the expected limiting values. Analysis of the events at early interaction times, of the order of 1 fm/c, indicates that the observed transverse momentum increases with both rapidity density and energy density.

The simultaneous direct mass measurements of 21 neutron-rich nuclei ranging from ${}_{}{}^{19}{}_{}{}^{}\mathrm{C}$ to ${}_{}{}^{37}{}_{}{}^{}\mathrm{P}$ have been performed with a new type of recoil spectrometer. The masses of ${}_{}{}^{19}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{27–28}{}_{}{}^{}\mathrm{Ne}$, ${}_{}{}^{32–34}{}_{}{}^{}\mathrm{Al}$, ${}_{}{}^{36}{}_{}{}^{}\mathrm{Si}$, and ${}_{}{}^{37}{}_{}{}^{}\mathrm{P}$ have been determined for the first time. No evidence of an increase in the two-neutron separation energy as noted for ${}_{}{}^{31–32}{}_{}{}^{}\mathrm{Na}$ is observed for ${}_{}{}^{30–32}{}_{}{}^{}\mathrm{Mg}$ and ${}_{}{}^{32–34}{}_{}{}^{}\mathrm{Al}$.

Partial decay schemes for the very neutron-rich nuclei ${}_{}{}^{142}{}_{}{}^{}$,144Ba and ${}_{}{}^{146}{}_{}{}^{}\mathrm{Ba}$ have been determined by the study of γ-γ coincidences in ${}_{}{}^{252}{}_{}{}^{}\mathrm{Cf}$ fission fragments. Interlaced positive- and negative-parity levels connected by fast electric dipole transitions are observed in ${}_{}{}^{144}{}_{}{}^{}\mathrm{Ba}$ and ${}_{}{}^{146}{}_{}{}^{}\mathrm{Ba}$ above spin 7ħ. This is similar to the situation in some light actinide nuclei, where the data have been interpreted in terms of reflection-asymmetric shapes.

The nuclear matrix element for 2ν double-beta decay is calculated within the quasiparticle random-phase approximation. It is shown that the decay matrix element passes through zero as a function of the strength $g^{\mathrm{pp}}$ of the particle-particle component of the spin-isospin polarization force, neglected previously. The analysis of electron capture/${\beta }^{+}$ decay rates for semimagic neutron-deficient nuclei suggests values for $g^{\mathrm{pp}}$ in the very vicinity of this zero, which gives rise to long lifetimes. The qualitative features of nuclear ββ decay are illustrated with the example of an exactly soluble model.

The pion spectra observed in the inclusive double-charge-exchange reactions ${}_{}{}^4{}_{}{}^{}\mathrm{He}$(${\pi }^{+}$,${\pi }^{\mathrm{-}}$)4p and ${}_{}{}^4{}_{}{}^{}\mathrm{He}$(${\pi }^{\mathrm{-}}$,${\pi }^{+}$)4n are strikingly different from those in heavier nuclei, exhibiting a prominent peak at high outgoing pion energies. The shapes of these spectra, while qualitatively consistent with two sequential single-charge-exchange processes, are not yet quantitatively understood.

We suggest that electron and positron peaks seen in large-Z heavy-ion collisions originate in the decay of nontopological solitons consisting of a quasielectron and quasipositron which are formed in a new vacuum phase.

Data for the ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$(${\pi }^{+}$,2p) reaction at Tπ=160 MeV were obtained for a number of angle pairs. The resultant angular correlations for $T_1$+$T_2$>160 MeV (guaranteed pion absorption) peak at a separation angle corresponding to absorption on a deuteron at rest. However, simple estimates of initial- and final-state scatterings suggest that less than 50% of the absorption cross section arises from absorption on nucleon pairs. The data show little evidence for scattering of pions before absorption on nucleon pairs.

Levels in ${}_{}{}^{158}{}_{}{}^{}\mathrm{Yb}$ have been established up to 38ħ in the yrast band and about 30ħ in two sidebands. Below spin 20, the similarity to the isotone ${}_{}{}^{156}{}_{}{}^{}\mathrm{Er}$ is striking, but up to spin 34 ${}_{}{}^{158}{}_{}{}^{}\mathrm{Yb}$ remains rather collective while ${}_{}{}^{156}{}_{}{}^{}\mathrm{Er}$ becomes triaxial and evolves toward an oblate shape. This appears to result from small shifts in particle-alignment (backbend) frequencies; a proton alignment occurs before neutron ones in ${}_{}{}^{158}{}_{}{}^{}\mathrm{Yb}$, whereas the reverse is true in ${}_{}{}^{156}{}_{}{}^{}\mathrm{Er}$.

The possible effects of different off-shell extrapolations of πN scattering are investigated for NN scattering based on the relativistic unitary three-body model. The conventional Δ-isobar model with a soft form factor is found not to lead to a successful description of the pion-production cross section. A refined model which includes the background interactions enables us to use harder form factors, bringing about marked improvements in reproducing the data.

A model-independent multipole analysis of ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$(e,e’p) and ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$(e,e’α) coincidence data, taken at three momentum transfers 0.39<q<0.68 ${\mathrm{fm}}^{\mathrm{-}1}$, yields both E1 and E2/E0 form factors and the respective multipole strength distributions in the giant-resonance region of ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ ($E_x$=14–22 MeV). While the deduced E1 strength agrees well with previous results, the total extracted E2/E0 strength is about twice the value found with isoscalar projectiles indicating the presence of large isovector E2/E0 contributions in the region of the isoscalar E2/E0 giant resonances.

Time-dependent Hartree-Fock theory is used to study fusion in ${}_{}{}^{16}{}_{}{}^{}$O${+}^{16}$O collisions. The Hamiltonian density is obtained from Skyrme forces including the spin-orbit interaction. The inclusion of spin has a dramatic effect on the observed dissipation for central collisions. At a center-of-mass energy of 34 MeV, fusion is found for all angular momenta less than the experimental critical angular momentum. Thresholds for inelastic scattering increase to a bombarding energy per nucleon of about 9 MeV. The decrease in transparency is in general agreement with experiment.

A new value for the deuteron binding energy of B(d)=2.388 176 8(24)×${10}^{\mathrm{-}3}$ u is reported based on an absolute wavelength determination of the 2.2-MeV n-p capture γ ray. Derived values of the n-H and n-p mass differences are also given. We also derive $M_n$=1.008 664 919(14) u. We note that the uncertainties in the neutron-mass data are now dominated by uncertainties arising from mass spectroscopy.

On the basis of very general dynamical properties of antinucleon-nucleon coupling it is shown that the (p¯,n¯) reaction should be a highly selective probe of longitudinal spin excitations.

Nuclear resonance fluorescence measurements with linearly polarized bremsstrahlung were performed to determine parities of bound dipole transitions in ${}_{}{}^{206}{}_{}{}^{}\mathrm{Pb}$. A new $1^{+}$ level at 5800 keV was found, which has almost the same strength as the isoscalar M1 transition in ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$. Twenty-four further dipole states in ${}_{}{}^{206}{}_{}{}^{}\mathrm{Pb}$ below 7.6 MeV possess negative parity.

Quasielastic nucleon-transfer cross sections have been mea- sured at energies ≊35% above the Coulomb barrier for ${}_{}{}^{58}{}_{}{}^{}$,64Ni ${+\mathrm{}}^{112}$,116,120,124Sn. The systematic trends were studied over the range of systems, which span a factor of 2 in neutron excess N-Z. The observed magnitude of the cross sections and their surface localization suggest that quasielastic processes play an important role in the average nucleus-nucleus potential, a quantity of considerable recent interest in near-barrier collisions of heavy systems.

There is evidence that the highest-spin states observed in nuclei are basically rotational, but that each state emits a distribution of γ-ray energies rather than a single energy. We have measured the width of this distribution and the fraction of the population that emits it, for several (unresolved) γ-ray energy regions in ${}_{}{}^{160}{}_{}{}^{}\mathrm{Er}$. These widths may be related to a damping of the rotational states at the high level densities through which these cascades flow.

We measured the mass and kinetic-energy partitioning in the spontaneous fission of ${}_{}{}^{258}{}_{}{}^{}\mathrm{Fm}$, ${}_{}{}^{259}{}_{}{}^{}\mathrm{Md}$, ${}_{}{}^{260}{}_{}{}^{}\mathrm{Md}$, ${}_{}{}^{258}{}_{}{}^{}\mathrm{No}$, and ${}_{}{}^{260}{}_{}{}^{}]$. All fissioned with mass distributions that were symmetric. Total-kinetic-energy distributions peaked near either 200 or 235 MeV. Surprisingly, these energy distributions were skewed upward or downward from the peak in each case, except for ${}_{}{}^{260}{}_{}{}^{}]$, indicating a composite of two energy distributions. We interpret this as a mixture of liquid-drop-like and fragment-shell directed symmetric fission, although theory had not anticipated this phenomenon.

The asymptotic normalization constants $C_2$ and $C_0$ for ${}_{}{}^3{}_{}{}^{}$H→n+d are calculated by the 34-channel triton wave functions obtained for the Argonne, the Paris, and the de Tourreil–Rouben–Spring two-nucleon potentials with the Tucson-Melbourne three-nucleon potential. These two-nucleon potentials without the three-nucleon potential yield the ratio $C_2$/$C_0$ at most of 0.04. The Tucson-Melbourne potential makes the value of $C_2$/$C_0$ increase about 10%. This ratio is linearly correlated with the triton binding energy without regard to the potential, provided that the potentials have the same asymptotic (one-pion exchange) behavior. From this relationship, we deduce the value of $C_2$/$C_0$ to be 0.0432±0.0015.

We argue that existing Σ-hypernuclear data do not unambiguously determine the Σ-nuclear spin-orbit splitting ${\epsilon }_p$, and suggest that the reactions ${}_{}{}^7{}_{}{}^{}(K^{\mathrm{-}}$,${\pi }^{+}$${)}_{\Sigma }^7$H, ${}_{}{}^{13}{}_{}{}^{}(K^{\mathrm{-}}$,${\pi }^{+}$${)}_{\Sigma }^{13}$ Be, and ${}_{}{}^{13}{}_{}{}^{}(K^{\mathrm{-}}$,${\pi }^{\mathrm{-}}$${)}_{\Sigma }^{13}$ C are well suited for a unique determination of ${\epsilon }_p$.

β-decay half-lives have been measured for eight neutron-rich isotopes produced by bombardment of a ${}_{}{}^{181}{}_{}{}^{}\mathrm{Ta}$ target with an ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$ beam at 30 MeV/nucleon. The previously unknown half-lives of ${}_{}{}^{14}{}_{}{}^{}\mathrm{Be}$ (4.2±0.7 ms) and ${}_{}{}^{17}{}_{}{}^{}\mathrm{C}$ (202±17 ms) have been obtained along with the half-lives of ${}_{}{}^9{}_{}{}^{}\mathrm{Li}$, ${}_{}{}^{11}{}_{}{}^{}\mathrm{Li}$, ${}_{}{}^{12}{}_{}{}^{}\mathrm{Be}$, ${}_{}{}^{14}{}_{}{}^{}\mathrm{B}$, and ${}_{}{}^{15}{}_{}{}^{}\mathrm{B}$. This experiment represents the first half-life measurements using the Michigan State reaction product mass separator.