Angular correlations between binary fission fragments have been measured in coincidence with light charged particles for 64, 129, 199, and 269 MeV ${}_{}{}^3{}_{}{}^{}\mathrm{induced}$ reactions on a ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ target. Linear momentum transfer and missing linear momentum have been determined for a broad range of light-charged-particle energies $E_{\mathrm{LCP}}$ and emission angles ${\theta }_{\mathrm{LCP}}$. Average momentum transfer increases from a fraction of beam momentum for small detection angles to nearly full momentum transfer at backward angles. The missing momentum depends primarily on ‘‘available energy’’ $E_{\mathrm{av}=E_{\mathrm{beam}\mathrm{-}{E}_{\mathrm{LCP}}}}$, but neither on beam energy $E_{\mathrm{beam}}$ nor light particle detection angle. Backward proton and deuteron emission is incompatible with statistical evaporation following complete or incomplete fusion.

Two bremsstrahlung amplitudes in the special two-energy-two-angle approximation, which are relativistic, gauge invariant, and consistent with the soft-photon theorem, are derived for bremsstrahlung processes with or without scattering resonances. These two amplitudes include the first two terms in the series expansion of the bremsstrahlung amplitude in powers of the photon energy but they are independent of any derivative of the elastic T matrix with respect to the total energy squared s or the momentum transfer squared t. It is found that the special two-energy-two-angle approximation provides an excellent description of almost all the available ${\pi }^{\pm }$pγ and $p^{12}$Cγ data.

We have done a microscopic calculation of the s-wave optical potential for the pion-nucleus system at low energies, 0≤$T_{\pi }$≤100 MeV, using a description based on hadronic degrees of freedom. We have obtained, separately, the real and imaginary parts of the optical potential coming from one-body and two-body processes. We have also separated the imaginary part of the potential associated to absorption and to quasielastic channels. We find that the imaginary part of the absorption channel is independent of the energy (within the range of energies considered here) in agreement with a recent empirical determination. We compare our results with phenomenological potentials obtained by fits to the empirical data. The comparison shows a good qualitative agreement. We discuss the dependence of the optical potential on the πN amplitudes, taken as an input in this model, and we find that a more repulsive isoscalar πN s-wave amplitude would provide better consistency between the π-nucleus theoretical results and the π-nucleus data. New experiments to provide more accurate πN phase shifts at low energies would be welcome.

We justify the inclusion of the rho meson in the Bonn potential in terms of the NN¯→ππ helicity amplitude analysis. The tensor observables are well reproduced with the resulting interaction. Consequences for the momentum dependence of the spin-longitudinal and spin-transverse effective interactions are discussed.

A phenomenological optical-model analysis is performed for the elastic scattering of alpha particles on ${}_{}{}^{40.42}{}_{}{}^{}$,44,48Ca at 1.37 GeV. Two geometries are considered for optical potentials, i.e., the traditional Woods-Saxon form and the double-Woods-Saxon form which can represent a change of the potential shape from the Woods-Saxon one. Among them, the best-fit potential has a ‘‘Mexican-hat’’ shape which is characterized by a long-ranged and weak attractive part in the surface region and a repulsion in the central region. From discussions on shape dependence of chi-square values, reaction cross sections, volume integrals, notch tests, and global potentials, a reasonable shape of the real part of the optical potential is suggested to be the ‘‘Mexican-hat’’ shape at this energy.

An electromagnetic current operator is deduced from the most general form of the extended pion-nucleon vertex function using the minimal substitution prescription. It is proved that the sum of the obtained current operator and the isolated-pole contribution satisfies the Ward-Takahashi identity derived for the pion photoproduction. The minimal-coupling interaction is applied to the calculation of the one-pion exchange current regularized by the pion-nucleon form factors. It is found that the one-pion exchange current operator including hadronic and electromagnetic form factors satisfies the Ward-Takahashi equation for the nucleon-nucleon interaction.

The reaction ${}_{}{}^3{}_{}{}^{}\mathrm{He}$(${\pi }^{+}$,pp)p was measured at $T_{\pi }$=350 and 500 MeV in a kinematically complete experiment. Separate contributions from two-body and three-body pion absorption are clearly seen in recoil momentum distributions. The two-body angular distributions closely follow the shape of the free πd→pp cross section, although the number of deuterons estimated from the two-body yield is larger than the value 1.5 expected from isospin coupling and observed previously at lower energies. Comparison with a simple impulse approximation model suggests some of the enhancement may arise from binding of the quasideuteron, although absorption on T=1 (pn) pairs and the higher density of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ may also be a factor. The strength of the three-body component falls off with bombarding energy with roughly the same slope as for the two-body component, and accounts for ≊45% of the total absorption cross section, a larger fraction than reported previously below the (3,3) resonance. The three-body matrix element ‖$M_3$${\Vert }^2$ displays an angular dependence at both energies which is suggestive of initial-state interactions. No evidence of final-state interactions is seen.

We investigate the scaling function in the asymptotic limit of inclusive scattering for cases where the interactions contain a hard core. For a particle bound in a potential we give an analytic expression for the correction to the standard impulse approximation result. For the response of a many-body system the same correction is obtained as a finite multiple-scattering series. The approach to the asymptotic limit is studied numerically in a simple model.

Atomic screening effects on the electron-neutrino angular correlation coefficient $a_0$ and the β asymmetry coefficient $A_0$, in allowed transitions, are studied. It has long been known that the dominant screening effect on the spectrum is the replacement, in the factor which represents the phase space of the β particle, of W, the energy with which the β particle emerges, by W-$V_0$, the energy with which it is born; $V_0$ is the energy of interaction of the β particle at the origin with the potential generated there by the atomic electrons. [One also replaces the momentum p=p(W) by p’=p(W-$V_0$).] One might well expect a similar result for screening effects on $a_0$ and $A_0$, which include the influence of the nuclear Coulomb potential—and this intuitive expectation is shown to be the case. One need merely replace the velocity of emergence v=v(W) in the correlation functions by the velocity at birth, v’=v(W-$V_0$). As for the case of the spectrum, the effect can be obtained by using a static approximation, with the atomic electrons unaffected by the β particle, and with the screening potential treated to second order; the effect of virtual or real excitation of the atomic electrons is negligible. The screening effect is of order ${10}^{\mathrm{-}4}$ for most superallowed and mirror image transitions (presently, both theory and experiment for superallowed transitions—with implications for electro-weak theory and the standard model—give ft values accurate to about one part in ${10}^3$); it can be as large as 20% for some pure Gamow-Teller transitions, for which the nuclear matrix element does not enter into the analysis of $a_0$ and $A_0$.

Fast neutrons were produced with deuteron beams of 27 MeV and 800 nA from the ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$${(}^2$H,n) reaction. These neutrons induced, in turn, natural-uranium fission. Samples of ${}_{}{}^{123}{}_{}{}^{}\mathrm{Ag}$ were obtained by means of on-line mass separation techniques applied to the fission products. The half-life of the ${\beta }^{\mathrm{-}}$ decaying ${}_{}{}^{123}{}_{}{}^{}\mathrm{Ag}$ was measured to be 0.35±0.04 s in agreement with previously reported data. The energy level scheme of ${}_{}{}^{123}{}_{}{}^{}\mathrm{Cd}$ was built from the obtained experimental results and is reported for the first time. Spins and parities for the most important states were suggested based upon logT values obtained from measured γ-ray transition intensities. The most important characteristics are discussed and nuclear structure properties are inferred.

The four-body equations of Alt, Grassberger, and Sandhas are solved in the version where the (2)+(2) subamplitudes are treated exactly by convolution, using one-term separable Yamaguchy nucleon-nucleon potentials in the ${}_{}{}^1{}_{}{}^{}\mathrm{S}_0^{}{}_{}{}^{}$ and ${}_{}{}^3{}_{}{}^{}\mathrm{S}_1^{}{}_{}{}^{}$${\mathrm{-}}^3$${\mathrm{D}}_1$ channels. The resulting $j^p$${=1/2\mathrm{}}^{+}$ and ${(3/2\mathrm{}}^{+}$ three-body subamplitudes are represented in a separable form using the energy-dependent pole expansion. Converged bound-state results are calculated for the first time using the full interaction, and are compared with those obtained from a simplified treatment of the tensor force. The Tjon line that correlates three-nucleon and four-nucleon binding energies is shown using different nucleon-nucleon potentials. In all calculations the Coulomb force has been neglected.

Ground-state properties of odd-A nuclei near closed shells are calculated using self-consistent, relativistic mean-field models of baryon-meson dynamics. Contributions from σ, ω, and ρ mesons and the photon are included. Comparisons are made between linear and nonlinear mean-field models, and with calculations including vacuum polarization in a local density approximation. Results are given for (intrinsic) binding energies, rms radii, magnetic and quadrupole moments, currents, and elastic magnetic scattering form factors, with comparisons to other calculations and to experiment. Bulk systematics are well reproduced by the nonlinear model and, as expected, isoscalar magnetic moments in light nuclei are close to Schmidt predictions for all models. At higher momentum transfer, currents are enhanced compared to nonrelativistic single-particle predictions, in disagreement with experiment. Extensions to include pions and derivative corrections to the vacuum polarization current are discussed.

We present a systematic study of single-particle and collective transverse current multipoles in the ground-state band of odd-A axially symmetric deformed nuclei. We analyze the interplay between single-particle and collective contributions to the total transverse form factors for elastic and inelastic scattering in a number of nuclei ${(}^{169}$Tm, ${}_{}{}^{177}{}_{}{}^{}$,179Hf, ${}_{}{}^{239}{}_{}{}^{}\mathrm{Pu}$), which exemplify different possibilities of ground-state $k^{\pi }$ bands ((1/$2^{+}$,(7/$2^{\mathrm{r}\mathrm{-}}$,(9/2+) and of odd-Z or odd-N character. We also discuss the dependence of form factors and static moments on the mean field used to generate the ground-state wave function. The dominant contribution is found to come from the odd nucleon, except in the low momentum transfer region (q<1 ${\mathrm{fm}}^{\mathrm{-}1}$) where the core is manifest through its interference with the single-particle amplitude.

The interacting-boson-fermion-approximation and triaxial models were used to calculate excitation energies and mixing ratios for the N=80 nuclei, ${}_{}{}^{139}{}_{}{}^{}\mathrm{Pr}$, ${}_{}{}^{141}{}_{}{}^{}\mathrm{Pm}$, and ${}_{}{}^{143}{}_{}{}^{}\mathrm{Eu}$. For low-lying negative- and positive-parity states both models yield roughly the same numbers, in good agreement with experimental results. For high-lying states we find that the interacting-boson-fermion-approximation model describes the level structure considerably better than the triaxial model. On the other hand, the triaxial model gives more satisfactory results in predicting the mixing ratios.

By considering a number of nonrelativistic potential models, the relationship between the ${}_{}{}^3{}_{}{}^{}\mathrm{S}_1^{}{}_{}{}^{}$ scattering length and the root-mean-square radius of the deuteron is studied. It is found that this relationship for certain classes of potentials is characterized by approximately straight line graphs similar to the one obtained by Klarsfeld et al. for a set of realistic nucleon-nucleon interactions. The implication of this study is that nonrelativistic nucleon-nucleon potentials of the types considered must include nonlocal components in order to be able to predict simultaneously the experimental triplet S-wave scattering length and the root-mean-square radius of the deuteron.

The mean-free path of protons is calculated in nuclear matter and in finite nuclei using the extended Skyrme interaction. The Green’s function technique is employed for infinite nuclear matter to carry out the calculations analytically. The connection to finite nuclei is established and results are compared to data extracted from reaction cross sections and optical-potential fits for three closed-shell nuclei. Fixing the radius parameter as in the interpretation of the measurements leads to reasonable agreement within the accuracy of the data.

A potential containing a one-pion-exchange tail and regularized at the origin by means of three parameters is used to construct several families of deuteron wave functions, which are employed in the assessment of the influence of the inner parts of the potential over observables such as $r_m$, η, and Q. The off-energy shell extrapolation of the results is considered, so as to provide guidelines for the treatment of other systems such as the triton. We also show that, provided the central potential contains a one-pion-exchange tail, the value of η is determined with great precision by just the inner part of the tensor component of the interaction.

We discuss the importance of the $J^P$=$0^{+}$,T=0→$J^P$=$0^{-}$,T=1 pionlike excitation in ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$, comparing it with results for smaller nuclei. Spin-isospin strength distribution effects due to high-lying nucleon-hole and Δ-hole excitations combined with the Landau-Migdal residual interaction are studied in an exact finite-nucleus calculation. We also present a comparison with a Fermi gas calculation in the local density approximation. We find important renormalization effects including interesting enhancement and quenching for different regions of the momentum transfer, which may be relevant and useful in explaining available experimental results for light nuclei. We demonstrate that studies on heavier nuclei will give complementary information on the diamesic renormalization and finite-system effects in the spin-isospin mode that is not available in the case of smaller nuclei.

The high-spin states of the N=88 isotones: ${}_{}{}^{154}{}_{}{}^{}\mathrm{Dy}$, ${}_{}{}^{156}{}_{}{}^{}\mathrm{Er}$, and ${}_{}{}^{158}{}_{}{}^{}\mathrm{Yb}$ are studied in the interacting-boson-plus-two-fermion-pair model. It was found that the high-spin states above and around the second backbends of ${}_{}{}^{156}{}_{}{}^{}\mathrm{Er}$ and ${}_{}{}^{158}{}_{}{}^{}\mathrm{Yb}$ could be interpreted as having two fermion pairs in addition to bosons. The yrast states much higher than the second backbends cannot be correlated in the model. Possible extensions of the model are discussed.

The ${\omega }^2$-weighted sums $W_L^{\mathrm{}\left(2\right)\mathrm{}}$(k) of the longitudinal response of two-, three-, and four-body nuclei are calculated with realistic nuclear forces, and exact (A=2) and variational (A=3 and 4) wave functions. These and the ω-weighted sums $W_L$(k) are used to estimate the unmeasured longitudinal response at ω>$E_{\max }$. The Coulomb sums obtained by integrating the measured response up to ω=$E_{\max }$ and the estimated response at ω>$E_{\max }$, are in good agreement with the theoretical predictions in light nuclei. The ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ and ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ data show the presence of proton-proton correlations, although they are not accurate enough to allow for a quantitative determination of the size of the repulsive core in the nucleon-nucleon interaction.