Alpha-particle energy spectra and angular distributions with respect to the estimated spin direction of residual nuclei have been measured in heavy-ion fusion reactions. The spin direction was determined for each event by measuring the γ-ray angular correlation patterns using the Spin Spectrometer. Measurements were made for the compound nuclear systems ${}_{}{}^{110}{}_{}{}^{}\mathrm{Sn}_{}^{\mathrm{*}}{}_{}{}^{}$(94 MeV), ${}_{}{}^{114}{}_{}{}^{}\mathrm{Sn}_{}^{\mathrm{*}}{}_{}{}^{}$(80 MeV), ${}_{}{}^{138}{}_{}{}^{}\mathrm{Nd}_{}^{\mathrm{*}}{}_{}{}^{}$(82 MeV), ${}_{}{}^{164}{}_{}{}^{}\mathrm{Yb}_{}^{\mathrm{*}}{}_{}{}^{}$(67 MeV), and ${}_{}{}^{170}{}_{}{}^{}\mathrm{Yb}_{}^{\mathrm{*}}{}_{}{}^{}$(135 MeV) at the indicated excitation energies as a function of the alpha-particle energy and γ-ray multiplicity. The anisotropy coefficients below the evaporation Coulomb barrier show distinct differences from ${}_{}{}^{110}{}_{}{}^{}\mathrm{Sn}_{}^{\mathrm{*}}{}_{}{}^{}$ to ${}_{}{}^{170}{}_{}{}^{}\mathrm{Yb}_{}^{\mathrm{*}}{}_{}{}^{}$. These results and the shapes of the alpha-particle spectra are compared with statistical model calculations that incorporate deformation effects in the optical model transmission coefficients. The ${\mathrm{Sn}}^{\mathrm{*}}$ data can be explained without invoking deformation effects other than the ones included in the experimental yrast lines. However, for the heavier ${\mathrm{Yb}}^{\mathrm{*}}$ systems, a considerable spin-dependent deformation in the α-emission barriers is required. For these systems the α emission below the barrier is a sensitive probe for deformation that samples a broad range of excitation energies in the decay sequence.

Measurements are reported for (a) 50 MeV ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$${+}^{12}$C elastic and inelastic scattering to the $2^{+}$ (4.44 MeV), $0^{+}$ (7.65 MeV), and $3^{\mathrm{-}}$ (9.64 MeV) states in ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, (b) 20 MeV ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$${+}^{12}$C elastic scattering, (c) 50 MeV ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$${+}^{16}$O elastic and inelastic scattering to the unresolved $0^{+}$/$3^{\mathrm{-}}$ (6.05/6.13 MeV) and $2^{+}$/$1^{\mathrm{-}}$ (6.92/7.12 MeV) states in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, and (d) 50 MeV ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$${+}^9$Be elastic and inelastic scattering to the 5/$2^{\mathrm{-}}$ (2.43 MeV) state in ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$. Data were measured out to approximately 100${\mathrm{°}}_{\mathrm{c}.\mathrm{m}.\mathrm{}}$. A mid-angle plateau characteristic of ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ scattering in the 5–10 MeV/nucleon energy range is confirmed in the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ scattering but is not so apparent in the ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$ scattering.

Two energy-dependent, six-parameter optical model potentials, both of which describe ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$${+}^{12}$C elastic scattering at ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ bombarding energies of 11, 20, 24, 30, 50, 60, 99, 156, and 210 MeV through the forward angle region before the plateau, are coupled with an angular momentum dependent imaginary potential. The results show improved descriptions of the plateau region and back angle scattering and a better description of 30 MeV ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$${+}^{12}$C vector analyzing power data than has previously been published. The ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$${+}^{12}$C inelastic scattering data are described by distorted-wave-Born-approximation calculations. Results of a double folded analysis of ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$${+}^{12}$C elastic scattering at the above energies show a systematic variation of the double folded normalization, N, and the imaginary volume integral. ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$${+}^{16}$O, ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$ elastic scattering data are analyzed with optical model and double folded potentials and the inelastic scattering data are described with distorted-wave-Born-approximation calculations.

The momentum distribution of nucleons in colliding ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$${+}^{16}$O system is studied with the Vlasov equation in the incident energy region of 20–100 MeV/nucleon. A shift of the momentum distribution to higher momenta is observed until the time of full overlap of two nuclei. It is attributed to the acceleration of the colliding nuclei, and discussed in terms of the newly defined potentials acting between two excited nuclei. The acceleration of colliding excited nuclei is even larger than that in the elastic channel at 40–100 MeV/nucleon. This is due to the dynamical change of the density distribution avoiding high density.

The concept of nuclear friction is considered from the point of view of regular versus chaotic motion in an atomic nucleus. Using a realistic nuclear Hamiltonian it is explicitly shown that the frictional description of the gross features of nuclear collisions is adequate if the system behaves chaotically. Because of the core in the Hamiltonian, the three-body nuclear system already reveals a structure of the phase space rich enough for this concept to be applicable.

The effect of valence protons in sub-barrier fusion reactions has been investigated. Excitation functions of residual masses were measured for the reactions ${}_{}{}^{35}{}_{}{}^{}\mathrm{Cl}$+A(N=28), i.e., ${}_{}{}^{35}{}_{}{}^{}\mathrm{Cl}$${+}^{50}$Ti, ${}_{}{}^{51}{}_{}{}^{}\mathrm{V}$, ${}_{}{}^{52}{}_{}{}^{}\mathrm{Cr}$, ${}_{}{}^{54}{}_{}{}^{}\mathrm{Fe}$, and ${}_{}{}^{54}{}_{}{}^{}\mathrm{Cr}$ from 0.85 to 1.5 times the Coulomb barrier. The data show no systematic isotonic dependence of the fusion or residual mass excitation functions in spite of the positive Q values for some nucleon transfer channels.

Prescission (${\nu }_{\mathrm{iso}}$) and postscission (${\nu }_{\mathrm{post}}$) neutron multiplicities have been measured for the reactions p${+}^{235,236,238}$U at several projectile energies between 12.7 and 25.6 MeV in coincidence with binary fragments. Separation of ${\nu }_{\mathrm{iso}}$ from ${\nu }_{\mathrm{post}}$ was achieved under the assumption of isotropic emission in the respective source frames. Both multiplicities increase with initial excitation energy ${\mathit{E}}_{\mathrm{CN}}^{\mathrm{*}}$ with comparable rates Δ${\mathit{E}}_{\mathrm{CN}}^{\mathrm{*}}$/Δν≊17±3 MeV. ${\nu }_{\mathrm{iso}}$(${\mathit{E}}_{\mathrm{CN}}^{\mathrm{*}}$) extends existing data of heavy-ion induced fusion-fission with ${\mathit{E}}_{\mathrm{CN}}^{\mathrm{*}}$≥50 MeV; for ${\mathit{E}}_{\mathrm{CN}}^{\mathrm{*}}$≥20 MeV it is incompatible with the transition-state model and cannot be reproduced without a delay time for the fission competition in the order of 3×${10}^{\mathrm{-}20}$–${10}^{\mathrm{-}19}$ s. The fragment mass dependence ${\nu }_{\mathrm{post}}$(m) shows a clear sawtooth structure for all three targets at ${\mathit{E}}_{\mathit{p}}$=12.6 MeV that is gradually washed out with increasing ${\mathit{E}}_{\mathit{p}}$ or decreasing total kinetic energy TKE, because the heavier fragment receives most of the additional excitation energy. The nuclear temperatures of the heavy fragments exceed those of the light ones, but seem to approach each other with increasing fragment excitation.

Nonrelativistic full-folding optical model potentials for nucleon elastic scattering have been calculated and applied to proton scattering on ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ and ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ at energies between 135 and 500 MeV. The optical potentials were calculated in momentum space by folding the mixed target density with the off-energy-shell free t matrix derived from the Paris nucleon-nucleon potential. The energy dependence and knockon exchange terms of the t matrix were included explicitly. Significant differences were observed between observables calculated from the full-folding model and conventional tρ approximations to it. At proton energies near and below ∼400 MeV, the full-folding model provides a substantial improvement in the description of the data compared to tρ approximations. These results demonstrate the importance of accurate treatments of the off-energy-shell properties of effective interactions as well as the mixed density in calculating nonrelativistic optical potentials for intermediate energy nucleon scattering. Exploratory calculations at 500 MeV together with those at lower energies suggest the need for an improved description of the nucleon-nucleon interaction at higher energies.

Absolute ${\mathrm{\pi }}^{\pm }$p differential cross sections have been measured at incident pion energies of 30.0, 45.0, and 66.8 MeV, using active targets of scintillator plastic (${\mathrm{CH}}_{1.1}$) to detect recoil protons in coincidence with scattered pions. Statistical uncertainties are typically ±3%; systematic uncertainties are ±2%. The results are consistent with two earlier measurements by this group employing different experimental techniques at 67 MeV and higher incident pion energies. The ${\mathrm{\pi }}^{\mathrm{-}}$p cross sections are in good agreement with currently accepted phase-shift analyses, but the corresponding ${\mathrm{\pi }}^{+}$p predictions are typically 15% higher at large angles than the ${\mathrm{\pi }}^{+}$p cross sections reported here.

The reaction ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$(${\mathrm{\pi }}^{+}$,pp) was studied with good energy resolution for an incident pion energy of 160 MeV. The angular correlation of the outgoing protons was measured for ${\mathrm{\theta }}_{\mathrm{lab}}$=30°, 75°, and 130°. From these angular correlations the contribution from direct two-nucleon absorption was extracted. A Monte Carlo calculation modeling the absorption process in terms of initial-state scattering of the pion before absorption, two-nucleon absorption, and final-state scattering of the outgoing nucleons is compared to the data. We conclude that within this framework the two-nucleon mechanism can account for less than half of the total absorption cross section in ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$. We report results for the low-energy coincidence proton spectra (down to 5 MeV) which suggest that most of these protons come from evaporation. Angular correlation data for the reaction ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$(${\mathrm{\pi }}^{\mathrm{-}}$,pp) are also presented.

We present a theory of deep-inelastic scattering from light nuclei that may be formulated in the target rest frame. (In our approach we can avoid the ambiguities that arise when boosting wave functions of light nuclei to an infinite momentum frame.) The resulting theory is applicable at relatively low values of momentum transfer and allows for a systematic treatment of off-mass-shell effects. We calculate the asymmetry in polarized leptoproduction from polarized ${}_{}{}^2{}_{}{}^{}\mathrm{H}$ and ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ targets and also provide expressions for the spin-independent and spin-dependent structure functions of these nuclei.

We present predictions for the asymmetry for deep-inelastic scattering of polarized leptons from polarized ${}_{}{}^2{}_{}{}^{}\mathrm{H}$ and ${}_{}{}^3{}_{}{}^{}\mathrm{He}$. These results are relevant to a proposed experiment that will test the validity of the Bjorken sum rule.

Inelastic scattering of 162 MeV ${\mathrm{\pi }}^{\mathrm{-}}$ and ${\mathrm{\pi }}^{+}$ was used to study the previously known ${\mathit{J}}^{\mathrm{\pi }}$=$8^{\mathrm{-}}$ stretched transitions in ${}_{}{}^{60}{}_{}{}^{}\mathrm{Ni}$. A consistent analysis of data from electron and pion scattering to stretched states using both harmonic oscillator and Woods-Saxon wave functions (unbound as necessary) was performed for ${}_{}{}^{60}{}_{}{}^{}\mathrm{Ni}$ and three other nuclei: ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$, and ${}_{}{}^{54}{}_{}{}^{}\mathrm{Fe}$. The experimental pion scattering cross sections were reproduced by distorted-wave impulse approximation calculations using wave functions from (e,e’) with a normalization factor N that generally varied from 1 to 5. The ratio of the total isoscalar to the total isovector strength ranged from 0.2 to 1.2. The use of Woods-Saxon wave functions in the analysis did not significantly improve the fits to the angular distributions.

The full folding optical potential for the elastic scattering of protons from ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ and ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ at 200 MeV is calculated. The fully off-shell free nucleon-nucleon t matrix, at a fixed energy, derived from the Paris potential and harmonic oscillator nuclear single-particle wave functions are used for both systems. The calculated observables show that the optimal factorization approximation provides a good description for both nuclei.

The longitudinal asymmetry in p→p scattering due to weak exchange of a charged pion is recalculated using a more realistic strong NN interaction to evaluate the effect of initial and final state rescattering. The pion-exchange contribution to the asymmetry at medium energy is smooth and equals 0.5×${10}^{\mathrm{-}7}$ at 800 MeV. This pion contribution has to be added to the conventional rho and omega contribution which, at this energy, has the same sign and about the same size. The total result, about 1.0×${10}^{\mathrm{-}7}$, should be compared to the experimental value at 800 MeV which is 2.4±1.1×${10}^{\mathrm{-}7}$.

Phenomenological analysis of double charge exchange scattering of pions shows that there is a sizable isotensor term in the optical potential at resonant energies. In an earlier paper we proposed that this term could be expected to reflect coupling of the elastic and analog channels to particular nonelastic channels with specific isospin structure. In this paper we present detailed models for this channel coupling, based on pion absorption and correlated double scattering. It is shown that any of the models could contribute to the isotensor potential with the appropriate phase. New predictions of isospin dependence of the potential are given.

We investigate the importance of gamma-ray correlations in nucleon-nucleus scattering. Coincidence observables can give information about the scattering amplitude that is not accessible in noncoincident (p,p’) experiments and can provide sensitive tests of different theoretical models. We have performed relativistic and nonrelativistic calculations with special emphasis on observables sensitive to composite spin-convection current amplitudes. We present calculations of coincidence cross sections as well as longitudinal and sideways analyzing powers using the $0^{+}$→$1^{+}$ excitation as an example. We have compared our results with coincidence cross section data for the first $1^{+}$, T=1 state in ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$. The experimental results seem to indicate a clear preference for the relativistic predictions.

In this work, we explore the NN→πNN reaction within a relativistic model for the NN and πNN coupled systems consistent with two- and three-body unitarity. After describing the theoretical input, we concentrate on some exclusive pp→pn${\mathrm{\pi }}^{+}$ observables. These are compared with the available data and with predictions from other models. In particular, we examine systematically the dependence of some spin observables on various components of the dynamical input. We identify and isolate some problems related to the present approach and we point out possible directions for future research.

A separable representation of the Argonne ${\mathit{v}}_{28}$ potential is presented. The potential includes delta isobar degrees of freedom within a coupled channel formalism. The separable potential was developed mainly for applications to nuclear matter. A quite high degree of accuracy was then reached to fulfill the requirements set by such calculations. The expansion was also extended above the NΔ threshold to allow for the evaluation of the average nuclear potential felt by the delta inside nuclear matter.

Elastic scattering of ${\mathrm{\pi }}^{\pm }$ on ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$, ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$, ${}_{}{}^{40,48}{}_{}{}^{}\mathrm{Ca}$, ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$, and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ at energies around the (3,3) resonance is studied within the framework of the strong absorption model of Frahn and Venter. The parameters thus obtained are used in the analysis of the inelastic scattering of pions leading to the lowest $2^{+}$ state in ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$. A reasonably good account of the scattering processes (elastic and inelastic) is given by the simple model.

Angular correlations of coincident gamma transitions have been measured in ${}_{}{}^{142}{}_{}{}^{}\mathrm{Ce}$ following the ${\mathrm{\beta }}^{\mathrm{-}}$ decay of fission product ${}_{}{}^{142}{}_{}{}^{}\mathrm{La}$ (${\mathit{T}}_{1/2}$=93 min) using a spectrometer consisting of a Ge and a Ge(Li) detector. The measurements were made on 14 direct and 13 skip cascades. Spin assignments were made to the levels at 2181 keV ($3^{+}$), 2727 keV ($1^{+}$), 3612 keV ($2^{+}$), and 4043 keV ($2^{+}$). In addition several previous spins assignments to other levels were confirmed. The multipole mixing ratios δ for 23 transitions were determined from the present results.