Pion double-charge-exchange cross sections have been measured at forward angles for targets of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$, ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$, ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$, and ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ at incident pion energies of 120–210 MeV. Angular distributions were obtained at 164 MeV for the lightest ${(\mathrm{}}^{12}$C) and heaviest ${(\mathrm{}}^{40}$Ca) targets. Pions corresponding to excitation energies up to 25 MeV in the final nuclei have been detected. Double differential cross sections $d^2$σ/dΩ dE are presented and the dependence on target mass, incident pion energy, excitation energy, and scattering angle has been investigated. The summed cross sections show a much smoother energy dependence than the ground state transition and mass dependence as $A^p$, with p varying with excitation energy rougly from -2 to -1. The excitation functions for the discrete nonanalog transitions to the first $2^{+}$ state in ${}_{}{}^{12}{}_{}{}^{}$O and ${}_{}{}^{40}{}_{}{}^{}$Ti have been measured.

The optical-model potential at low energy is defined by the requirement that it yields a suitably defined energy average of the scattering function. It is argued that the quantities which appear in the expression for this energy average derived by Lane and Thomas in the framework of R-matrix theory can be identified with those which appear in a convenient parametrization of the fine structure cross section. The accuracy of this identification is illustrated with the help of various picket-fence models. We discuss the independence of the results with respect to the size of the energy domain covered by the experimental data and to the nature of the R-matrix boundary parameters. Also we discuss terms that can be included if one wishes to discuss fluctuations about a smooth average.

Photoproton spectra from the ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}$(γ,p) reaction were measured at various bremsstrahlung end point energies in the giant dipole resonance region. Absolute cross sections for eight partial photoproton channels were determined with the use of an artificially constructed quasi-monochromatic photon spectrum. Their integrated cross sections were compared with spectroscopic factors for proton pickup reactions leading to corresponding residual states. The (γ,${\mathrm{p}}_{\mathrm{tot}}$) cross section was derived from proton yield measurements. These data lead to an estimated semidirect contribution to the photoproton reaction of at least 60%, and to an approximate determination of the configurational splitting.

A two-axis flat-crystal spectrometer has been used to measure accurately gamma-ray energies up to 2 MeV from the reaction ${}_{}{}^{35}{}_{}{}^{}\mathrm{Cl}$(n,γ). This represents a fourfold extension of the range of direct optically based gamma-ray energies. The crystals and spectrometer have performed in a manner which demonstrates that sub-ppm measurements are possible at energies ≳2 MeV. The reported transition energies (in eV) are 517 077.41±0.23, 786 311.32±0.38, 788 437.43±0.44, 1 164 885.74±0.48, 1 951 197.06±0.58, and 1 959 413.45±8.45. The sum rule is satisfied by three of the lines (786 keV+1165 keV=1951 keV) within an uncertainty of ∼1 ppm.

Resonance parameters for ${}_{}{}^{31}{}_{}{}^{}$P+n were determined, largely from (n,γ) cross-section data measured by time of flight. The energy range investigated extended from 2.6 to 500 keV, with the lowest energy resonance found at 26.75 keV. The 30-keV stellar reaction rate is dominated by this resonance, giving 1.74+0.09 mb for a temperature kT=30 keV. The thermal capture data are examined within the framework of the direct reaction mechanism.

The photoneutron cross sections for ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$ [σ(γ,1n) and σ(γ,2n)] have been measured up to 36 MeV using monochromatic photons. The cross section for the emission of a single neutron displays a very prominent resonance near 15 MeV which appears to decay primarily to the ground state of ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$. The (γ,2n) cross section is sharply peaked at 26 MeV and is large compared with those for ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$. The integrated total photoneutron cross section up to 36 MeV is 126±12 MeV mb (61% of the Thomas-Reiche-Kuhn sum-rule value). The ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$ photoneutron cross sections are interpreted in terms of the reaction kinematics and the competition among the particle channels in order to provide information on the isospin properties of the major E1 states in ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$ and on the validity of the weak core-coupling model.

Neutron spectra from the ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$(d,n${)}^{28}$Si reaction have been measured with an energy resolution of better than 10 keV. Bombarding energies ranged from 2.5 to 8 MeV, permitting various regions of excitation in ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ to be populated with 1 to 3 MeV outgoing neutrons. Levels corresponding to contaminants could be identified by the energy shift with angle. We have identified four new levels below 13 MeV and 22 new levels above 13.4 MeV. The (d,n) reaction at low bombarding energies appears to be nonselective; we observe every previously known level as well as the new ones, with the only exception being those which are unresolved ($E_1$-$E_2$≲8 keV) from neighboring levels. We are not able to deduce the spins and parities of these levels from the present data.

The cross sections for elastic and rearrangement four-nucleon reactions have been calculated above the breakup threshold in the K-matrix approximation to the Grassberger-Sandhas integral equations. In the first order K-matrix approximation we find that the ${}_{}{}^2{}_{}{}^{}\mathrm{H}$(d,p${)}^3$H and ${}_{}{}^2{}_{}{}^{}\mathrm{H}$(d,n${)}^3$He cross sections at low energies are sensitive to the properties of the nuclear force and to its tensor component even at higher energies. At higher energies good agreement is obtained with experiment, but there is quantitative and qualitative disagreement with the data at lower energies. We also performed K-matrix calculations including the principal value part of the (2+2) propagators by means of the generalized-unitary-pole-expansion/energy-dependent-pole-expansion for the (2+2) subamplitudes. At lower energies this improved the agreement with data in the ${}_{}{}^2{}_{}{}^{}\mathrm{H}$(d,n${)}^3$He reaction considerably, and in the case of p${+\mathrm{}}^3$He elastic scattering even resulted in a spectacular improvement in the forward direction. The lack of structure in the differential cross section [e.g., absence of a second maximum in the ${}_{}{}^2{}_{}{}^{}\mathrm{H}$(d,n${)}^3$He cross section] persisted, however. This qualitative disagreement is probably mainly due to the omission of the contribution of the p-wave three-body subsystem amplitude in the calculations.

We present angle integrated spectra for the (p,n) reaction with 25 MeV protons on targets of ${}_{{\mathrm{}}^{50}}{}^{}{}_{}{}^{}$,52,${\mathrm{}}_{24}^{53}$Cr, and on ${}_{26}{}^{58}{}_{}{}^{}\mathrm{Fe}$, ${}_{27}{}^{59}{}_{}{}^{}\mathrm{Co}$, ${}_{28}{}^{60}{}_{}{}^{}\mathrm{Ni}$, and ${}_{29}{}^{63}{}_{}{}^{}\mathrm{Cu}$. These spectra are compared with two-quasiparticle state densities for proton-particle–neutron-hole configurations, calculated using Nilsson-model single-particle energies. The influence of shell structure on the precompound spectra, previously shown for the $g_{9/2}$ neutron shell closure, is shown here for the $f_{7/2}$ neutron and proton shells. Semiquantitative agreement is shown between experimental results and calculated two-quasiparticle densities. The parameter space of pairing energy, deformation, and oscillator stiffness is explored. Precompound spectra near shell closures are in better agreement with partial state densities from Nilsson-model considerations than with results from more commonly used equidistant spacing models.

The neutron decay of the giant resonance region between 13.0 and 18.0 MeV in ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$ has been studied in an (α,α’n) coincidence experiment at $E_{\alpha }$=104 MeV. In the region of the giant quadrupole resonance between 13 and 16 MeV, additional strength with multipolarity L≥4 was identified. For the resonant strength in the region of the giant monopole resonance, a direct decay component of about 12% can be estimated. In addition, evidence for a preequilibrium decay was found.

The fine structure of the low-energy octupole resonance was studied for ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$, ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$, and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ by proton inelastic scattering at $E_{\mathrm{p}=65\mathrm{}}$ MeV. The low-energy octupole resonance was composed of many discrete levels of L=3 states. The total energy-weighted sum rule fraction of more than 10% was found in every nucleus. Especially in ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$, the energy-weighted sum rule fraction amounted to 15%. The strength was finely fragmented in ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$, but less fragmented in ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$. It is suggested that the ‘‘degree of fragmentation’’ is correlated with the excitation energy and the distribution of the low-lying quadrupole phonon states.

A critical examination of sum rules derived previously by Austern and Vincent (post form) and by Udagawa and Tamura (prior form) demonstrates that agreement between the two approaches is obtained if certain approximations implicit in the Udagawa-Tamura prior-form derivation are avoided. We examine the relation of the two approaches to singularities of the post-form distorted wave Born approximation matrix element and to the procedures for reduction of a many-body theory by use of effective operators in a model space. The two-step heuristic model is seen to be invalid for prior-form inelastic breakup; it is necessary to take account of nuclear excitations during projectile breakup. Careful treatment of the non-Hermiticity of kinetic energy operators with respect to continuum wave functions is required.

Inelastic scattering of 134-MeV polarized protons has yielded angular distributions of both cross sections and asymmetries for the $J^{\pi }$${=0\mathrm{}}^{+}$–$8^{+}$ members of the ground state rotational band of ${}_{}{}^{176}{}_{}{}^{}\mathrm{Yb}$, and the $0^{+}$–$6^{+}$ members for ${}_{}{}^{182}{}_{}{}^{}\mathrm{W}$. Deformation parameters ${\beta }_2$, ${\beta }_4$, and ${\beta }_6$ have been extracted from an analysis using coupled channels calculations for scattering from a deformed optical potential. Multipole moments of the potential are determined and are compared with similar moments obtained from electromagnetic measurements and other hadron scattering experiments at different energies. Comparisons are made with moments obtained from Hartree-Fock calculations and from a liquid drop model.

We have made a direct measurement of the radiative tail of the eleastic peak from several tungsten targets. The measured data have been compared to the results expected for both internal and external bremsstrahlung contributions. Even for targets as thick as 4% of a radiation length of tungsten, agreement between the results of the experiment and the predictions of the theory has been found to be unexpectedly good.

The spin-flip probability has been measured using the Schmidt particle-γ coincidence technique for the reaction ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ leading to the first excited state of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ at energies $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}$=17.28 and 26.88 MeV. Both forward and backward angles in the center of mass system were studied, the latter only at the lower bombarding energy. The particle-γ angular correlation has also been measured in the reaction plane. The data have been analyzed by treating the elements of the density matrix of the final $2^{+}$ state as unknown parameters using a least squares fitting procedure. The results of this analysis have been compared with reaction model calculations, and suggest that the observed spin-flip probability can be accounted for without the necessity of introducing a phenomenological spin-dependent component into the nucleus-nucleus optical potential.

We analyze the symmetry-conserving-variational-dynamics and the time-dependent-generator-coordinate methods showing their equivalence for a large class of problems. The application to actual calculations involving the restoration of the rotational symmetry in nuclear dynamics is examined together with the Gaussian overlap hypothesis. It is shown that the range of validity of the combined approach is restricted to very weak symmetry breaking. The relative location of the method in the context of variational approximations to the dynamics is established as well as the various relations among different procedures.

The theory of fission fragment angular distributions is examined and the universally used expression is found to be valid only under restrictive assumptions. A more general angular distribution formula is derived and applied to recent data of high spin systems. At the same time it is shown that the strong anisotropies observed from such systems can be understood without changing the essential basis of standard fission theory. The effects of reaction mechanisms other than complete fusion on fission fragment angular distributions are discussed and possible angular distribution signatures of noncompound nucleus formation are mentioned.

A reanalysis of selected fission fragment angular distributions is made using formulae derived in the previous paper. In contrast to previous results it is concluded that the recent heavy-ion-induced fission data is consistent with standard assumptions of fission, although it is suggested that incomplete fusion plays a major role in high energy heavy ion collisions leading to fission.

We have measured the energy spectra for the emission of long-range α particles from the spontaneous fission of ${}_{}{}^{250}{}_{}{}^{}\mathrm{Cf}$, ${}_{}{}^{256}{}_{}{}^{}\mathrm{Fm}$, and ${}_{}{}^{257}{}_{}{}^{}\mathrm{Fm}$, and for tritons and protons from the spontaneous fission of ${}_{}{}^{250}{}_{}{}^{}\mathrm{Cf}$ and ${}_{}{}^{256}{}_{}{}^{}\mathrm{Fm}$. We have determined α, triton, and proton emission probabilities and estimated total light-particle emission probabilities for these nuclides. We compare these and known emission probabilities for five other spontaneously fissioning nuclides with the deformation energy available at scission and show that there is a possible correlation that is consistent with a one-body dissipation mechanism for transferring release energy to particle clusters.

We calculate the coupling parameters of several dibaryon resonances (${\mathrm{B}}_2$) to the π-d channel in terms of the more fundamental ΔN-${\mathrm{B}}_2$ and NN-${\mathrm{B}}_2$ couplings. We compare the results with values obtained from phenomenological fits and show that at least in one case (for the $J^P$${=4\mathrm{}}^{+}$ resonance at 2.48 GeV) the latter ones are not compatible with a deuteronlike structure of the dibaryon systems.