A quite general formalism which allows one to compute the pion double-charge-exchange differential cross section in the context of the shell model has been developed. Compact formulas taking into account the full momentum and spin dependence of the elementary amplitude are given. These formulas hold for any nuclear angular momenta as well as any pion-nucleus partial waves. Thus the differential cross section depends on a quantity ${\mathit{B}}_{\mathit{l}1}$${\mathit{l}}_2$ifJ(${\mathit{k}}_1$,${\mathit{k}}_2$) which is a function of the magnitude of the pion momenta ${\mathit{k}}_1$,${\mathit{k}}_2$ and is composed of three factors: (1) the nuclear matrix element involving the states (i) and (f) expressed in terms of tensor operators T(${\mathit{a}}^{\mathrm{°}}$a); (2) the essentially ‘‘geometric’’ aspects of the elementary double-charge-exchange amplitude which are pretty independent of any specific model; (3) a radial integral which contains the ingredients of specific models as well as the distortion of the mesons involved.

Giant isoscalar monopole and quadrupole resonances are introduced into the SU(3) limit of the interacting boson model by means of S and D bosons simulating collective particle-hole excitations, in addition to the usual s and d bosons, representing either collective particle or hole pairs in the valence shell. The evaluated giant resonance energies, as well as the matrix elements of E0 and E2 transitions from the giant resonance levels to the $0_1^{+\mathrm{-}}$$2_1^{+\mathrm{-}}$$4_1^{+}$ members of the ground-state band, are utilized in coupled-channel calculations of giant resonance excitation through inelastic alpha scattering by the transitional isotopes ${}_{}{}^{148}{}_{}{}^{}\mathrm{Sm}$ and ${}_{}{}^{154}{}_{}{}^{}\mathrm{Sm}$: the calculated differential cross sections are then compared with experimental data.

The double-humped potential barriers in actinide nuclei in the fission direction have been parametrized using three different procedures, namely, the smoothly joined parabolic segments, third-degree polynomials passing through and with zero slopes at the successive extremum points, and straight-line segments connecting the successive extremum points. The fission penetrabilities through the barriers and the ground-state spontaneous fission half-lives for a wide variety of 25 actinide nuclides have been calculated for these different parametrizations. Our results clearly indicate that while the third-degree polynomial and the straight-line parametrizations of the double-humped fission barrier lead to approximately similar results on the fission penetrability and fission half-lives, the corresponding results using the smoothly joined parabolic segment parametrization differ significantly by almost two to five orders of magnitude depending on the specific type of the fissioning nucleus and on the parameters of its corresponding double-humped fission barrier.

The α${+}^{12}$C system is investigated in the generator coordinate method, where the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ nucleus is described by three α particles located on the apexes of an equilateral triangle. The ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ wave functions are projected out on the $0^{+}$ and $2^{+}$ states. By modifying the size of the triangle, we analyze the importance of clustering effects in ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ on ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ bound states, and on α${+}^{12}$C phase shifts. These effects are found to be reduced when the total spin of the α${+}^{12}$C system increases. The coupling between the α${+}^{12}$C($0^{+}$) and α${+}^{12}$C($2^{+}$) channels also decreases when α clustering is introduced in ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$. We obtain high-energy resonances in the α${+}^{12}$C scattering. These resonances, located between 15 and 30 MeV in the center of mass, are suggested to be Pauli resonances, analog to the well-known forbidden states in the two-cluster model.

A method to calculate heavy nucleus collision cross sections based on the analogy between the Glauber-Sitenko multiple scattering theory and statistical theory of liquids is suggested. Extensive use is made of the scaled particle method in the Rowlison-Widom model to calculate the free energy and the partition function.

Measurements of vector analyzing power have been carried out for the (d→,t) reaction on targets of ${}_{}{}^{54}{}_{}{}^{}\mathrm{Cr}$, ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}$, and ${}_{}{}^{64}{}_{}{}^{}\mathrm{Ni}$ at deuteron energies of 15, 16, and 18 MeV. Data were taken over the angular range 10°–55° for transitions to low-lying states of ${\mathit{J}}^{\mathrm{\pi }}$=(1/2,3/2, 5) / 2 ,7/2${)}^{\mathrm{-}}$ using a position-sensitive counter telescope in the focal plane of an Enge spectrograph. Transitions to states of ${\mathit{j}}^{\mathrm{\pi }}$=3/$2^{\mathrm{-}}$ or 7/$2^{\mathrm{-}}$ show only slight dependence on incident energy, while those to states of ${\mathit{j}}^{\mathrm{\pi }}$=1/$2^{\mathrm{-}}$ or 5/$2^{\mathrm{-}}$ show a greater dependence, and greater variations between different states. Distorted-wave Born approximation calculations show at best qualitative agreement with the data. The results indicate that measurements of VAP for the (d→,t) reaction at low energies will not provide accurate estimates of j mixing for transitions on odd-A targets.

The ${}_{}{}^2{}_{}{}^{}\mathrm{H}$(t,tp)n reaction was investigated in a kinematically complete experiment with a tritium beam at energies around 35 MeV. Evidence was found for the ${}_{}{}^4{}_{}{}^{}\mathrm{H}$ ground state. Coincidence spectra were fitted by the contribution of quasifree processes, sequential decay through the ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ ground state, and the n-p final-state interaction. The best agreement with the data was obtained assuming the following ${}_{}{}^4{}_{}{}^{}\mathrm{H}$ ground-state parameters: ${\mathit{E}}_{\mathit{r}}$=3.1 MeV and ${\gamma }^2$=2.3 MeV.

Cross sections for the reaction ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$(p,2p${)}^{15}$N to the ground state and excited state at 6.32 MeV have been measured at an incident energy of 151 MeV. The data are in good agreement with distorted-wave impulse-approximation calculations. The factorization approximation is found to be valid for the region of phase space studied. The extracted spectroscopic factors are reasonably consistent with those determined in other experiments, and they are also compatible with results of a weak-coupling nuclear structure model.

Independent and cumulative yields in nearly symmetric fission have been measured for the first time by bombarding ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ with 20-MeV protons and with 18-, 25-, and 41-MeV deuterons. Isobaric charge dispersion has been determined in the A=110, A=112, and A=114 mass chains and, from asymmetric fission, in the A=80 mass chain. The average isobaric charges in the p+U reaction were 44.01±0.20 (A=110), 45.15±0.15 (A=112), and 45.74±0.15 (A=114). The widths (standard deviations) of the charge dispersion curves were 0.82±0.08 (A=112) and 0.54±0.08 (A=114). The average charges are roughly 0.3 unit higher than those calculated on the basis of the unchanged charge distribution model. The ground-state branch in the beta decay of ${}_{}{}^{80}{}_{}{}^{}\mathrm{Ge}$ was determined to be 65%. Altogether some 15 new neutron-rich isotopes have been found, the newest one being ${}_{}{}^{114}{}_{}{}^{}\mathrm{Ru}$ with a half-life of 0.53±0.06 s. An ion guide facility was used to separate the isobaric chains on-line from other fission products. Typical cumulative yields in a mass chain were on the order of 1000 atoms/μC, but for new isotopes independent yields as low as a few atoms/μC could be observed.

Differential cross sections for the ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ti}$(p,${\mathit{p}}_0$) and (p,${\mathit{p}}_1$) reactions were measured in the range ${\mathit{E}}_{\mathit{p}}$=3.08–3.86 MeV with an overall resolution of about 350 eV. Resonance parameters were extracted for 716 levels with a multilevel, multichannel R-matrix code. These parameters include resonance energy, total angular momentum, parity, total width, and elastic partial width. Six analog states were identified. After correction for missing levels the 1/$2^{+}$ and 1/$2^{\mathrm{-}}$ level densities are nearly equal and the J dependence agrees with statistical model expectations.

Absolute cross-section measurements for the photofission reactions of ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$, ${}_{}{}^{\mathrm{nat}}{}_{}{}^{}\mathrm{Pb}$, ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}$, ${}_{}{}^{232}{}_{}{}^{}\mathrm{Th}$, ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$, and ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}$ nuclei have been performed at an incident photon energy of 69 MeV using monochromatic and polarized photon beams and dielectric fission-track detectors. Nuclear fissility values have been obtained and results are in agreement with those from other laboratories, although in some cases discrepancies are observed between one other. For nuclei in the region of the actinides the fissility result is ≳0.4, while for Au, Pb, and Bi nuclei it only is ∼${10}^{\mathrm{-}3}$–${10}^{\mathrm{-}2}$. Results have been interpreted in terms of the primary Levinger’s quasideuteron nuclear photoabsorption followed by a mechanism of evaporation-fission competition for the excited nuclei. Shell effects have been taken into account, and they are clearly manifested when fissility is evaluated. The influence of photon polarization on photofission of ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ also has been investigated, and results have shown isotropy in the fragment azimuthal distribution.

Deuteron spectra at laboratory angles from 30° to 90° were measured in α+(Pb, Cu, and C) collisions at 800, 600, and 200 MeV/nucleon, and α+(Pb and C) collisions at 400 MeV/nucleon. The coalescence relation between protons and deuterons was examined for the inclusive part of the spectra. The size of the interacting region was evaluated from the observed coalescence coefficients. The rms radius is typically 4–5 fm, depending of the target mass. The proton and deuteron energy spectra corresponding to central collisions were fitted assuming emission from a single source moving with a velocity intermediate between that of the projectile and the target. The extracted ‘‘temperatures’’ are independent of the nature of the emitted particle, indicating that the fragments have a common source. The best fits were achieved for 200- and 400-MeV/nucleon reactions. Spectra of deuteron-like pairs, including real deuterons and neutron-proton pairs that may be contained in a larger nuclear cluster, are compared to the prediction of an intranuclear cascade model incorporating a clustering algorithm based on a classical coalescence prescription. Best agreements between experimental and predicted deuteron-like spectra occur for 800- and 600-MeV/nucleon collisions.

Coincident neutron-proton pairs were measured from the reaction ${}_{}{}^3{}_{}{}^{}\mathrm{He}$(γ,np)p with a 100-MeV bremsstrahlung beam. The energy and angle of the neutron and proton were used to reconstruct the photon energy, making this a kinematically complete experiment. Quasi-deuteron breakup was observed for photon energies from 45 to 95 MeV. The angular distribution of the np pairs was measured for opening angles from 122 to 202 degrees in the laboratory frame. The single-differential cross section in ${\mathrm{\Omega }}_{\mathit{p}}$ was determined at ${\mathrm{\theta }}_{\mathit{p}}$=81°, relative to deuterium, to range from 2.4 at 55 MeV to 1.7 at 95 MeV.

We have measured the inclusive neutron cross section as a function of neutron energy and angle at 15°, 30°, 45°, 60°, 120°, and 160° for the system Ag${(}^{36}$Ar,n) at 35 MeV/nucleon. All spectra can be fitted with a moving-source model consisting of a projectilelike source, an intermediate-rapidity source, and a targetlike source. Temperatures for the targetlike and intermediate-rapidity sources were found to be about 4 and 11 MeV, respectively. Neutron multiplicities for each were 5.6 and 1.0. These parameters are compared with those from the neutron inclusive measurement of Ag${(}^{14}$N,n) at 35 MeV/nucleon and with proton exclusive data from the reaction ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$+Ag at 30 MeV/nucleon.

Data from a kinematical coincidence experiment on the damped reaction ${}_{}{}^{165}{}_{}{}^{}\mathrm{Ho}$${+}^{74}$Ge at 8.5 MeV/nucleon have been reanalyzed. Although the new analysis confirms the presence of some correlations between the excitation-energy division and the mass asymmetry, the magnitude of these correlations is found to be significantly smaller than that previously reported. Proton-neutron symmetry of the mechanism of heat generation through nucleon exchange is revealed and a possible acceptor-donor asymmetry of this mechanism is discussed.

Angular distributions have been measured for $0^{+}$→$1^{+}$ transitions with the ${(}^{12}$C${,}^{12}$B) reaction on targets of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$,${\mathrm{}}^{26}$Mg, ${}_{}{}^{54}{}_{}{}^{}\mathrm{Fe}$,${\mathrm{}}^{58}$Ni, and ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$ and with the ${(}^{12}$C${,}^{12}$N) reaction on targets of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}$. The bombarding energy was E/A=70 MeV, and small-angle data were obtained. A comparison of the cross sections measured for the ${(}^{12}$C${,}^{12}$B) reaction with the results of distorted-wave-approximation calculations indicates that $0^{+}$→$1^{+}$ transitions are predominantly one step at E/A=70 MeV. The calculated cross sections are generally in good agreement (to within 40% in magnitude) with the measured cross sections, and the angular distributions are well described quantitatively in many cases. A correlation between cross sections and known Gamow-Teller (GT) strengths B(GT) for the corresponding transitions has been found. This correlation, which is weakly dependent on the target mass, establishes a calibration for the reactions. It is used to determine B(GT) values of astrophysical interest for two low-lying $1^{+}$ levels in ${}_{}{}^{56}{}_{}{}^{}\mathrm{Mn}$ from the cross sections measured for the ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}$${(}^{12}$C${,}^{12}$N${)}^{56}$Mn reaction. The results are compared with two shell-model calculations performed to obtain B(GT) for ${}_{}{}^{56}{}_{}{}^{}\to _{}^{56}{}_{}{}^{}$Mn transitions and with another calculation from the literature. Computational tests were performed to evaluate (a) the contribution to the cross sections of terms not present in nucleon-induced charge-exchange reactions and (b) the extent to which the cross sections provide a measure of GT strength.

Elastic π${\mathrm{-}}^{12}$C scattering at 800 MeV/c is investigated by the means of the Glauber theory and the optical-potential model. Various effects associated with the first-order potential are carefully examined as well as higher-order effects of nuclear correlations and pion absorption. A clear discrepancy persists between the calculation and the data. The calculation is extended to the single- and double-charge-exchange processes at 800 MeV/c.

The statistical model is used to illustrate the consequences of a successive binary decay mechanism as the initial nuclear excitation is pushed towards the limits of stability. The partition of the excitation energy between light and heavy fragments is explicitly calculated, as are the consequences of the decay of the primary light fragments to particle-bound residual nuclei which would be observed experimentally. The test nucleus ${}_{44}{}^{100}{}_{}{}^{}\mathrm{Ru}$ is considered at initial excitations of 100, 200, 400, and 800 MeV. Exit channels of n, p, and α and 100 clusters of 3≤Z≤20, 6≤A≤48 are considered from all nuclides in the deexcitation cascade. The total primary and final cluster yields are shown versus Z and initial excitation. The primary versus final yields are also shown individually for ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{26}{}_{}{}^{}\mathrm{Mg}$, and ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$. We show how multifragmentation yields will change with the excitation energy due to a successive binary decay mechanism. Measurements that may be prone to misinterpretation are discussed, as are those that should be representative of initial nucleus excitation.

The analyzing power ${\mathit{A}}_{\mathit{y}}$ for p+p elastic scattering at ${\mathrm{\theta }}_{\mathrm{lab}}$=8.64°±0.07° (${\mathrm{\theta }}_{\mathrm{cms}}$=18.1°) and at a bombarding energy of 183.1±0.4 MeV has been determined to be ${\mathit{A}}_{\mathit{y}}$=0.2122±0.0017. The error includes statistics, systematic uncertainties, and the uncertainty in bombarding energy and angle. This measurement represents a calibration standard for polarized beams in this energy range. The absolute scale for the measurement has been obtained by comparison with p+C elastic scattering at the same energy at an angle where ${\mathit{A}}_{\mathit{y}}$ is very nearly unity.

The angular distribution of neutrons emitted in ${(}^{11}$Li${,}^9$Li) breakup reactions is calculated directly from one of the reaction mechanisms, viz. Coulomb dissociation. The shape of the calculated distribution agrees quite accurately with recently measured neutron data. This provides a test of the calculated dipole strength in ${}_{}{}^{11}{}_{}{}^{}\mathrm{Li}$ at low excitations.