Differential cross sections for the double-isobaric-analog-state transition in the ${}_{}{}^{42}{}_{}{}^{}$,44Ca(${\pi }^{+}$,${\pi }^{\mathrm{-}}$) reactions were measured at an incident energy of 35 MeV and 40 degrees. The ${}_{}{}^{42}{}_{}{}^{}\mathrm{Ca}$ cross section (2.0±0.5 μb/sr) is nearly as large as those of the lighter T=1 nuclei and only slightly smaller than that previously measured for ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$ (2.4±0.7 μb/sr). The cross section for ${}_{}{}^{44}{}_{}{}^{}\mathrm{Ca}$ (1.1±0.3 μb/sr) is half of this amount. These results are surprising when compared with simple expectations and point to the importance of the nonanalog route contribution at low energies.

Several recent experiments using a proton beam have shown that nuclear-spin excitations in light nuclei appear relatively suppressed at low excitation energy but surprisingly enhanced at higher excitation. We present here a calculation based on energy-weighted sum rules which yields results consistent with spin-flip data in ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$. The calculation is further useful in showing the importance of 2p-2h coupling in producing asymmetric width as well as in demonstrating the effects of meson exchange currents. The prediction of an increase in spin-flip strength at high energy with increasing momentum transfer should be a useful test of the model.

Inelastic scattering of 5–11 MeV neutrons to the $3_1^{\mathrm{-}}$ state in ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ is reanalyzed in the distorted wave Born approximation using phenomenological potentials and form factors that explicitly reflect the ‘‘threshold anomaly’’ effects observed in the elastic scattering channel. A previously reported energy dependence of the deformation length ${\delta }_3$ is largely removed by this analysis. We conclude that dispersion corrections to the one-channel optical potentials are important in the off-diagonal elements of the potential matrix.

The tensor analyzing power $A_{\mathrm{yy}}$, vector analyzing power $A_y$, and cross section σ(θ) of the reaction ${}_{}{}^1{}_{}{}^{}(\mathrm{d}\to$,γ${)\mathrm{}}^3$He have been measured at a deuteron energy of 95 MeV, corresponding to photo- disintegration with 37 MeV photons. The total cross section is in good agreement with ${}_{}{}^3{}_{}{}^{}(\gamma$,p${)}^2$H measurements; $A_y$ and $A_{\mathrm{yy}}$ were both small and negative. $A_{\mathrm{yy}}$ is known to be sensitive to the ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ D-state amplitude, and all previous measurements of tensor analyzing powers have been made in an energy region where the initial state interaction between the proton and deuteron is strong. These data were interpreted using a plane-wave Born approximation model which has been successful in describing other measurements of $A_{\mathrm{yy}}$ at lower energies. Within the framework of this model, these measurements were found to be consistent with an asymptotic D-S state normalization ratio η=-0.029.

Lifetimes of high-spin states of ${}_{}{}^{159}{}_{}{}^{}$,160,161Yb, populated by fusion-evaporation reactions, have been measured by the recoil-distance technique. The data were collected in coincidence with a total-energy filter to provide some discrimination on reaction channel. The principal feature of the resulting transition quadrupole moments is a frequency-dependent reduction which is displayed by those bands with aligned quasiparticles. This seems to be mainly due to the influence of the favored $i_{13/2}$ quasineutron. Additional available data are surveyed and support this conclusion. Calculations using the cranked shell model and the cranked Hartree-Fock-Bogoliubov and cranked Nilsson-Strutinsky methods provide a qualitative description of the experimental observations. In addition, a satisfactory account is provided by recent calculations based on a fermion dynamical-symmetry model.

The level structure of ${}_{}{}^{83}{}_{}{}^{}\mathrm{Zr}$ was investigated via the fusion-evaporation reaction ${}_{}{}^{54}{}_{}{}^{}\mathrm{Fe}$${(}^{32}$S,2pn${)}^{83}$Zr at beam energies between 105 and 120 MeV using in-beam γ-ray spectroscopy techniques. γ transitions from the decay of ${}_{}{}^{83}{}_{}{}^{}\mathrm{Zr}$ were unambiguously identified by means of recoil-γ, neutron-γ, and x-ray-γ coincidences. The decay scheme was constructed on the basis of Compton suppressed γ-γ coincidences, delayed γ-γ coincidences, and angular distribution measurements. A total of 34 transitions were identified connecting 26 new energy levels and the previously known ground state. The lifetimes of two low-lying isomeric states were determined. A decoupled positive parity band built on the odd $g_{9/2}$ neutron configuration was observed up to spin (37/2ħ with the first band crossing due to proton alignment showing a sharp backbend at ħω=0.5 Mev. A strongly coupled negative parity band based on a ${(5/2\mathrm{}}^{\mathrm{-}}$ bandhead was observed up to spin (35/2ħ. The angular momentum alignment is discussed and compared to neighboring nuclei. A theoretical analysis was performed using the Woods-Saxon cranking model. The results of the calculation are consistent with the experimental findings for ${}_{}{}^{83}{}_{}{}^{}\mathrm{Zr}$ and its neighbors. Triaxial shapes are predicted for all observed bands in ${}_{}{}^{83}{}_{}{}^{}\mathrm{Zr}$. At higher angular momenta a transition to well-deformed prolate bands involving the $h_{11/2}$ intruder orbitals is expected.

This paper reports a measurement of the differential photoneutron cross section of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ at 65°, between $E_{\gamma }$=30 and 100 MeV. Tagged photons, monochromatic to within 2.6 MeV, were used, thus allowing the cross sections to a wide range of final states to be observed. The results are compared to the photoproton cross section of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, which was measured previously, under similar conditions. Comparisons are also made with calculations based on the quasi-deuteron model, and with calculations by Gari and Hebach, and Cavinato et al. These latter calculations incorporate two-body effects by the inclusion of meson exchange currents. The agreement between these calculations and the measured cross section is in contrast to predictions of a direct, single-nucleon knockout model of the reaction mechanism, indicating the importance of two-body effects in the photoreaction process for energies greater than 50 MeV.

Angular distributions of the differential cross sections for the elastic scattering of 210 MeV ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ from ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ (3°–61°) and ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$ (3°–48°) have been measured. The cross sections exhibit diffractive oscillations at small angles and exponential falloff characteristic of nuclear rainbow scattering at large angles. The data beyond the rainbow angle make it possible to obtain unique optical model potentials for the ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$+nucleus interaction, thus eliminating the discrete ambiguities inherent in the lower-energy studies. By truncating the angular distributions, data up to the rainbow angle could be fitted with several discrete ambiguous potentials. Extrapolation of the unique potentials to lower energies provides an energy dependence of the real potential volume integral given by $J_R$/6A=$J_R^0$/6A-β ln$E_{\mathrm{lab}}$ with $J_R^0$/6A≊800±30 MeV ${\mathrm{fm}}^3$ and β≊100 MeV ${\mathrm{fm}}^3$, a result which is essentially consistent with proton elastic scattering.

Angular, energy, and Z distributions of projectile-like and fission fragments were measured for the reaction ${}_{}{}^{197}{}_{}{}^{}$Au${+\mathrm{}}^{51}$V at $E_{\mathrm{lab}=447\mathrm{}}$ MeV. With increasing energy loss, the angular distribution evolves from a focused to an orbiting type, while the nearly Gaussian Z distributions broaden and drift to larger asymmetries. Extensive phenomenological analyses are presented for the angle-energy and charge-energy correlations. These data are compared in detail with results obtained from one-body transport model calculations. The effects of angular-momentum-dependent kinetic-energy fluctuations and of a reduced strength in the ‘‘wall friction’’ force are approximately taken into account. Good general agreement between data and model predictions is observed with friction forces of nominal strengths. The cross section for fusion-fission–like events, somewhat overestimated by the reaction model, is in reasonable agreement with the systematics provided by the ‘‘extra push’’ model parametrization.

Energy and angular distributions of heavy (Z≥4) projectilelike residues of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ have been measured at 100 MeV/nucleon with better than unit A and Z resolution. Global fits to the isotopic distributions show close correspondence to the relativistic results. Closer examination reveals angle dependent damping of the fragmentation peak. The dependence of this damping upon the target mass gives evidence that the scattering outside the grazing angle is to positive angles.

The yield ratios of light clusters (d,t${,}^3$He,α) to protons were measured for the reactions Nb + Nb and Au+Au for incident beam energies of 150, 250, 400, and 650 MeV/nucleon. The ratios are analyzed in the framework of the quantum statistical model and the specific entropy is extracted as a function of the participant proton multiplicity. The results are compared with predictions of the fireball model and relativistic mean field calculations.

Internal excitation of projectile-like fragments and target-like fragments was investigated for the system 12 MeV/nucleon ${}_{}{}^{48}{}_{}{}^{}$Ti${+\mathrm{}}^{150}$Nd, by measuring the discrete γ rays emitted by both fragments in coincidence with the charge-separated projectile-like fragments. Two quasielastic exit channels of the projectile-like fragments were studied: Z=20 and Z=22. Characteristic γ rays were used to determine the average masses of products, after separation and neutron evaporation, as a function of kinetic energy loss. Our results show that the mass-to-charge equilibration occurs quickly for the Z=20 exit channel, but is slower for the Z=22 channel. Comparison between the average masses of products with the masses calculated using the statistical model show that the excitation energy is divided approximately equally between the projectile-like and the target-like fragments for the Z=20 exit channel. The excitation energy appears to be divided equally up to ∼105 MeV of the kinetic energy loss corresponding to ∼36% of kinetic energy damping. This result is consistent with predictions made by the stochastic nucleon-exchange models for a small kinetic energy loss.

Quasi-elastic reactions were studied for ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$ beams at 330 MeV and ${}_{}{}^{64}{}_{}{}^{}\mathrm{Ni}$ beams at 341 and 380 MeV incident energy, respectively, on even-A Sn isotopes. Angular distributions were measured in the range 20°≤${\theta }_{\mathrm{lab}\mathrm{\le }55}$° using a magnetic spectrograph with a gas-filled focal-plane detector yielding single mass and charge resolution; generally individual states were not resolved. Cross sections for quasi-elastic one-neutron pickup and stripping reactions vary smoothly with the ground-state Q value. Total quasi-elastic transfer cross sections range from 340 to 640 mb, corresponding to 20–40 % of the total reaction cross section determined from the elastic scattering angular distributions. The distribution of the total cross section into the various reaction channels is discussed.

We discuss the properties of the transition operator for ${\mathrm{K}}^{+}$ photoproduction on a free proton and for hypernuclear associated production. The main points discussed are (i) the relation between the operators in the pseudoscalar and the pseudovector-derivative coupling schemes; (ii) the theoretical uncertainties embedded in the tree-level operator; (iii) the nuclear-structure effects and uncertainties in the relativistic many-body model based on the Dirac equation with large scalar and vector potentials.

We present a new formal approach for the calculation of the s-wave optical potential for pionic atoms which makes extensive use of the Lindhard function, its analytical properties, and its useful low density limit. The conventional parameters $b_0$ and $B_0$ are calculated and compared to results from empirical fits to pionic atom data. We show that the virtual excitation of ph-Δh components by the pion is the main source of the real part of $B_0$. Higher order effects from the polarization of the pion lead to some enhancement of Im$B_0$, providing values which are compatible with the empirical data. The real part of the potential suffers from larger uncertainties due to the off-shell extrapolation of the πN scattering amplitude.

Differential cross sections and analyzing powers are presented for the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$(p→,${\mathrm{\pi }}^{+}$${)}^{17}$O* reaction at $T_{\mathrm{p}}$=250, 354, and 489 MeV and compared with preliminary 200 MeV data as well as previously published data taken at other energies above and below the ${\Delta }_{1232}$ resonance region. The differential cross sections for each final state exhibit an energy dependence similar to that of the pp→d${\pi }^{+}$ reaction at equivalent center of mass energy and four-momentum transfer, as has been seen previously for (p,${\pi }^{+}$) reactions with other target nuclei. The shape of the analyzing power angular distributions varies with the ${}_{}{}^{17}{}_{}{}^{}\mathrm{O}_{}^{\mathrm{*}}{}_{}{}^{}$ nuclear final state. Some states exhibit broad similarities with that of the p→p→d${\pi }^{+}$ reaction, while others are markedly different.

Scattering models with either relativistic or nonrelativistic dynamics are used to predict elastic scattering observables in the forward angle, Coulomb-nuclear interference region for 500 and 800 MeV ${\mathrm{p}+}^{16}$O, ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$, and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$. At 500 MeV the differential cross sections for the relativistic model are 15–25 % larger than those of the nonrelativistic model. Ambiguities in the theoretical predictions which arise from empirical input used by the models and from approximations made in numerically evaluating higher order corrections are estimated and found to contribute ±2%–±6% to the uncertainty of the differential cross sections in the forward angle region at 500 MeV for ${\mathrm{p}+}^{40}$Ca and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$. The sensitivity of the relativistic model cross sections to the use of a variety of relativistic nuclear structure models and different prescriptions for the virtual NN¯ pair process for the projectile is investigated and found to be largest at 500 MeV.

To clarify the analysis of our existing backward proton scattering data in terms of high momentum components in nuclei, we have measured exclusive cross sections for the backward energetic protons in coincidence with the γ rays emitted by the target. At 200 MeV incident proton energy, the mass distribution of the residual nuclei from a ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ target suggests a single scattering reaction on a nucleon of the target. We have also performed large momentum transfer electron scattering on ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$ using a 640 MeV electron beam. These data analyzed within the quasi-two-body scaling approach display a scaling regime identical to the one previously observed for the protons. Both of these features give credence to the ‘‘single scattering,’’ basic assumption in the quasi-two-body scaling theory. The experimental momentum distribution is in good agreement with several theoretical predictions which include short range correlations.

The role of virtual negative-energy states, so-called pair terms arising from box and crossed-box diagrams and based on combinations of various meson exchanges, is investigated in detail in nucleon-nucleon scattering, in the framework of time-ordered perturbation theory. The effect of such contributions on N-N scattering phase shifts is non-negligible, especially in the ${}_{}{}^1{}_{}{}^{}\mathrm{S}_0^{}{}_{}{}^{}$ partial wave. The precise amount depends very sensitively on the type of form factor chosen.

A simple way to transform a two-body equal mass Dirac equation to a one-body Kemmer-Duffin-Petiau equation is shown. The procedure permits the reduction of higher-order kinetic and potential terms in the Dirac equation. The wave function of the relative coordinate splits naturally to a pseudoscalar meson trajectory tower of states of dimension five and a vector meson trajectory of dimension ten. The scheme is applied to the Salpeter equation with arbitrary local interactions and compared to the existing reduction procedures.