We have calculated theoretical angular distributions for exclusive ${\pi }^0$ production in C+C collisions at 84 MeV/nucleon using a quantum-coherent, microscopic, many-body formalism. We use a model spin, transition-spin, Δ-isobar-formation interaction that is expanded in angular momentum multipoles and we now have the results from a complete code that includes these multipoles to all orders which couple to shell-model information. Also, we calculate pion contributions coming from both the target and projectile and find that these contributions are important in determining the shape of the theoretical angular distributions. We compare the theoretical calculations to ${\pi }^0$ data and find that our results are similar to the shape of the data at higher pion energies and bear some similarity in trend to the pion bremsstrahlung model. We also find that the shape of the theoretical angular distribution is sensitive to shell-model information.

A procedure is developed for projecting out the relative angular momentum, spin- and isospin-zero α-like part of the wave function of four nucleons moving in a single-particle potential of arbitrary shape. Examples in the ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ nucleus and Ni-Zn regions are used to test and illustrate the procedure.

Quasiparticle dynamics, a computer simulation for nuclear reactions, is used to investigate reaction plane memory in intermediate-energy heavy-ion collisions. In particular, extensive simulations involving the generation of more than 20 000 events are performed for ${}_{}{}^{14}{}_{}{}^{}\mathrm{Sm}$ at 35A MeV. The gamma-ray circular polarization, as a function of trigger mass, energy, and angle, is shown to be a measure of the correlation between the trigger plane and the reaction plane. Calculations of the inclusive particle spectrum, as well as the polarization, are compared with experiment. The dependence of the calculated observables on the assumed in-medium nucleon-nucleon cross section is also investigated.

The α decay of Ru compound nuclei populated in ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$ on ${}_{}{}^{58}{}_{}{}^{}$,60,62,64Ni reactions at $E_{\mathrm{beam}=135\mathrm{}–}$185 MeV has been studied. Experimental data have been compared with statistical model calculations performed with two different computer codes. The quality of the agreement between calculations and experimental data was found, in one case, to depend on the compound nucleus populated. Comparing the results from the two computer codes, deviations in the predicted cross sections are evidenced which are due to the different parametrization of nuclear properties employed in the calculations. Statistical model calculations describe well the shape of experimental spectra if account is taken of changes in the phase space available to the decaying nucleus which are related to the onset of deformations at high spins. Fission competition strongly determines the alpha-particle cross sections at the higher bombarding energies which are systematically underestimated by the model calculations if transmission coefficients computed from optical model potentials are used.

Crystal-blocking angular distributions have been measured for projectile-like fragments produced in bombarding a 10-μm Ge crystal with a 1.76-GeV ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$ beam. Long time delays of the order of (6–12)×${10}^{\mathrm{-}18}$ s were extracted and gave a direct indication of important evaporation effects. The measured times can be reproduced using a broad distribution of primary fragments of the type predicted by the abrasion model, but with excitation energies from 15 to 50 MeV, which are higher than predicted by the model. The measured times can also be reproduced assuming a narrow primary mass distribution with highly excited fragments having excitation energies of about 150 MeV.

The ${\pi }^{\mathrm{-}}$/${\pi }^{+}$ yield ratio in 1.05 GeV/nucleon ${}_{}{}^{40}{}_{}{}^{}$Ca${+}^{40}$Ca interactions was measured using a magnetic spectrometer system. The ratio was found to be unity over the entire range of measurements covering ${\theta }_{\mathrm{lab}=10\mathrm{}}$°, 20°, 25°, 30°, 65°, and 90° and laboratory momenta 100≤$p_{\mathrm{lab}\mathrm{\le }350}$ MeV/c. The ratios exhibit no visible effect of Coulomb forces from the nuclear charge distributions.

We have measured cross sections for the formation of actinide transfer products in the reaction of 72-MeV ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ projectiles with ${}_{}{}^{254}{}_{}{}^{}\mathrm{Es}_{}^{\mathrm{g}}{}_{}{}^{}$ targets. The pattern of nuclide yields is similar to those observed in the reactions of heavier ions with ${}_{}{}^{254}{}_{}{}^{}\mathrm{Es}_{}^{\mathrm{g}}{}_{}{}^{}$. We have constructed the primary element yields from these results and show that the total cross section for transfer reactions is 58 mb. The total reaction cross section is about 300 mb. Lawrencium isotopes are formed with larger cross sections than are consistent with the trends of the transfer-product distributions; we explain this in terms of massive transfer, and model the lawrencium yields with an evaporation code.

The internucleus potentials of the ${}_{}{}^{16}{}_{}{}^{}\mathrm{-}_{}^{16}{}_{}{}^{}$O, ${}_{}{}^{12}{}_{}{}^{}\mathrm{-}_{}^{16}{}_{}{}^{}$O, ${}_{}{}^{12}{}_{}{}^{}\mathrm{-}_{}^{12}{}_{}{}^{}$C, and α${\mathrm{-}}^{16}$O systems are calculated by using the Skyrme-type forces in the framework of the canonical moving wave packet method. The volume integrals $j_v$ of the calculated potentials are compared with those of the real parts of the optical potentials which fit the data very well in a wide energy range. Compared with experiments, the calculated values of ‖$j_v$‖ are found to have too weak energy dependence and to be too small in the incident energy region lower than about 40 MeV/nucleon. Finite-range nuclear forces are constructed with least modification to the Skyrme-type forces such that they reproduce the same nuclear matter properties as the Skyrme-type forces, and the properties of the internucleus potentials are studied by these finite-range forces.

The finite-temperature self-consistent semiclassical calculation is carried out to determine the nucleon densities of some hot nuclei at thermal equilibrium with temperature T. These densities are applied, in the energy density formalism, to calculate the nucleus-nucleus optical potential and the corresponding fusion barrier between two hot nuclei. A moderate temperature dependence is found for the optical potential and fusion barrier.

We discuss methods for the calculation of the electromagnetic response tensor, $W_{\mu \nu }$, in terms of quark wave functions. We describe the consequences of various choices which can be made in the specification of the four-momentum of the quark and contrast the approximations we have made with those of the parton model.

We have made the first systematic precision measurement of the deuteron-deuteron total cross sections at 12 incident momenta in the range of 1.5–4.0 GeV/c on a proton synchrotron. The data were obtained by means of the transmission method covering the momentum transfer squared range of 0.001 to 0.009 (GeV/c${)}^2$ at each momentum. Our data show no anomalous structure in the excitation function and are in good agreement with Glauber model calculations including the effect of the Fermi motion of the nucleons in the deuteron except at 1.5 GeV/c, where the datum is lower than the calculated value.

Momentum distributions of triple differential cross sections for the reaction πd→πpn have been measured for 36 final-state pion-proton angle pairs at 228 MeV incident pion energy. The data are compared with earlier experimental results and with recent few-body calculations. In the region of quasifree elastic scattering the cross sections are typically lower than theoretical values by up to 30%. In regions away from quasifree scattering the general trends of the data are generally described, with best agreement on the low-momentum side of the distributions and with differences between theory and experiment as large as a factor of 10 in the worst cases. Together with the corresponding comparisons for the pion-deuteron elastic scattering and absorption channels, this failing might be an indication of the need to broaden the conventional calculations, or of the need to recognize an explicit quark contribution.

We report the observation of double isovector giant dipole resonances in (${\pi }^{+}$,${\pi }^{\mathrm{-}}$) and, for the first time, also in (${\pi }^{\mathrm{-}}$,${\pi }^{+}$) double-charge-exchange reactions at $T_{\pi }$=292 MeV. The resonances have been observed on nine targets covering a wide range of mass at Q values around ≊-50 MeV in (${\pi }^{+}$,${\pi }^{\mathrm{-}}$), but at significantly lower energy (Q=-33.8 MeV) in the inverse reaction on ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}$. The centroid energies in both reactions are very close to the energies at which the Δ$T_z$=±2 double giant dipole ($J^{\pi }$${=0\mathrm{}}^{+}$,$2^{+}$,ΔT=2) states are expected to appear. Angular distributions have been measured for the (${\pi }^{+}$,${\pi }^{\mathrm{-}}$) resonances on ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$${,}^{56}$, Fe, and ${}_{}{}^{93}{}_{}{}^{}\mathrm{Nb}$ and each is observed to have a quadrupole shape. Based on their energies, angular distributions, cross sections, and the comparison between the (${\pi }^{+}$,${\pi }^{\mathrm{-}}$) and (${\pi }^{\mathrm{-}}$,${\pi }^{+}$) data on ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}$, we identify the resonances as double giant dipole states (i.e. states arising from a charge-exchange dipole operator acting twice on the ground-state wave function). The data from the present and recent observations indicate that the newly discovered resonance is a general collective feature of all nuclei.

Neutral pion photoproduction on the nucleon near threshold is investigated using a dynamical model. Analytic properties of the final-state interaction amplitude in the energy region near ${\pi }^{+}$n production threshold are examined in detail. It is shown that the commonly used procedure, based on an analytical continuation of the K matrix to the unphysical region, is not compatible to an approach incorporating full off-energy-shell dynamics. Our calculation indicates that the final-state interaction amplitude derived from a dynamical model could involve large cancellation between the different pion photoproduction mechanisms. This leads to the surprising result that the final-state interaction effect due to the intermediate ${\pi }^0$p state can be as important as that due to the ${\pi }^{+}$n intermediate state. At threshold, we obtain &. This number is close to the measured value of &. No violation of the low-energy theorem is required to obtain good agreement between the calculated total cross sections and experimental data from threshold to about 400-MeV incident photon energy.

We discuss fits of the Landau-Milekhin model to the transverse momentum spectra measured in 200 GeV/c nucleus-nucleus collisions. It is observed that the data are fit by a range of anticorrelated values of the breakup temperature and the average transverse hydrodynamic velocity. These fits indicate that a better understanding of transverse flow in ultrarelativistic nuclear collisions is required to uniquely determine the breakup temperature of the system.

We have investigated the $0^{\mathrm{-}}$ ${}_{}{}^{96}{}_{}{}^{}\mathrm{Y}_{}^{\mathrm{g}}{}_{}{}^{}$ β decay to the levels of ${}_{}{}^{96}{}_{}{}^{}\mathrm{Zr}$. A detailed decay scheme comprised of 63 γ rays and 44 energy levels has been obtained from γ singles, γ multispectral scaling, and γ-γ and E0-γ coincidences. $Q_{\beta }$ was measured using the β-γ coincidence technique, while absolute E0 and γ-ray intensities were obtained from singles conversion electron and γ-ray spectra measured at beam saturation. The high sensitivity of the study was aimed at investigating the β feeding of levels with excitation enegy above 4 MeV. Although most of the new levels were found in this region, their total β feeding was found to be below 0.6%. The first-forbidden β-decay rate for $0^{\mathrm{-}}$ ${}_{}{}^{96}{}_{}{}^{}\mathrm{Y}_{}^{\mathrm{g}}{}_{}{}^{}$→$0^{+}$ ${}_{}{}^{96}{}_{}{}^{}\mathrm{Zr}_{}^{\mathrm{g}}{}_{}{}^{}$ has been calculated within the framework of the spherical shell model using a model space of π(0${\mathit{f}}_{7/2}$,0${\mathit{f}}_{5/2}$,1${\mathit{p}}_{3/2}$,1${\mathit{p}}_{1/2}$,0${\mathit{g}}_{9/2}$) 1${\mathit{p}}_{1/2}$,0${\mathit{g}}_{9/2}$)ν (${0\mathrm{g}}_{7/2}$,1${\mathit{d}}_{5/2}$,1${\mathit{d}}_{3/2}$,2${\mathit{s}}_{1/2}$) with limitations on the orbit occupancies. Additional evidence for meson enhancement of the timelike component of the axial current is obtained; the meson-exchange enhancement factor was found to be 1.75±0.30, where the uncertainty arises from the calculation.

Nuclear orientation and nuclear magnetic resonance measurements have been performed for ${}_{}{}^{106}{}_{}{}^{}\mathrm{Rh}$ oriented at low temperature in iron and nickel hosts. From the results of the temperature dependence measurements of nuclear orientation, the magnetic moment of ${}_{}{}^{106}{}_{}{}^{}\mathrm{Rh}$ was deduced as ‖μ${(}^{106}$Rh,$1^{+}$)‖=2.52(5)${\mathrm{\mu }}_{\mathit{N}}$, which is very different from the value of 3.07(9) ${\mu }_N$ reported previously. From the nuclear magnetic resonance on oriented nuclei measurements of ${}_{}{}^{106}{}_{}{}^{}\mathit{Ni}$, the magnetic hyperfine splitting frequency ‖g${\mu }_N$$B_{\mathrm{HF}/\mathrm{h}\mathrm{\Vert }}$ was determined to be 441.5(7) MHz. Using the hyperfine field $B_{\mathrm{HF}}$ (RhNi) of -22.49(5) T, the precise value of the magnetic moment of ${}_{}{}^{106}{}_{}{}^{}\mathrm{Rh}$ was deduced: ‖μ${(}^{106}$Rh,$1^{+}$)‖ =2.575(7) ${\mu }_N$. The electric quadrupole interaction has been measured using modulated adiabatic passage on oriented nuclei in a nickel single-crystal host. A broad distribution of the quadrupole splitting Δ${\nu }_Q$ is found, extending from 0 to 300 kHz.

In two separate experiments the half-life of ${}_{}{}^{10}{}_{}{}^{}\mathrm{C}$ has been measured to be 19.294±0.016 s and 19.300±0.041 s. This has resolved the previous disagreement in the literature and gives a final value of 19.290±0.012 s when combined with the other, concordant determinations. Only the branching ratio now needs to be remeasured to enable the ft value of the ${}_{}{}^{10}{}_{}{}^{}\mathrm{C}$ superallowed positron decay to be calculated with a precision of 0.1%.

The importance of pairing effects in the N=82 isotones is extensively investigated by studying the string of nuclei with A ranging from 135 to 151. The pairing Hamiltonian is treated by an equations-of-motion method which is strictly number conserving. The coupling strength is determined by an analysis of the properties of the even-mass isotones. The single-particle energies are extracted from the experimental spectra of ${}_{}{}^{137}{}_{}{}^{}\mathrm{Cs}$ and ${}_{}{}^{145}{}_{}{}^{}\mathrm{Eu}$ through use of the equations which give the energies of the seniority-one states in a way which is analogous to the inverse gap equation method. A detailed comparison of the calculated results with experimental data in even and odd nuclei provides firm evidence of the prominent role of proton pairing correlations in the 50–82 shell. It is found that non-negligible correlations are present in ${}_{}{}^{146}{}_{}{}^{}\mathrm{Gd}$.

When the low-energy octupole state and low-energy octupole resonance are considered as a single composite mode in A=24–54 even-even nuclei, a regular pattern for the energy centroids is found. The location of the energy centroid as a function of nuclear mass can be explained in terms of the effects of shell structure on collective octupole excitations. It is predicted that the energy of the centroid of the composite mode in the stable isotope ${}_{}{}^{50}{}_{}{}^{}\mathrm{Cr}$, where it has not yet been measured, is 5.7±0.4 MeV.