The experimental elastic scattering cross section is inverted into an optical potential using a rational parametrization of the scattering function. A regularized error analysis is carried out. The method is successfully applied to the system α${\mathrm{-}\mathrm{}}^{40}$Ca at 104 MeV.

The Boltzmann master equation as adopted for treating equilibration in heavy ion reactions has been modified to include pion production rates from (n,n), (n,p), and (p,p) collisions. We calculate neutral pion production cross sections for reactions of 35 MeV/nucleon ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ with ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$, ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$, and ${}_{}{}^{184}{}_{}{}^{}\mathrm{W}$ targets. We also calculate ${\pi }^0$ production cross sections for reactions of ${}_{}{}^{12}{}_{}{}^{}$C${+\mathrm{}}^{12}$C, ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$, ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ at beam energies of 60, 74, and 84 MeV/nucleon, and of 44 MeV/nucleon ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$ with ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$, ${}_{}{}^{119}{}_{}{}^{}\mathrm{Sn}$, and ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$. Results of these calculations are generally within a factor of 2 of experimental values. Compound nucleus excitations predicted for the equilibrated nuclei for the above reactions are also estimated for implications in a compound nucleus interpretation of the pion production mechanism.

The high-spin level structures of the nuclei ${}_{}{}^{95}{}_{}{}^{}$,97Ru have been studied via the ${}_{}{}^{92}{}_{}{}^{}\mathrm{Mo}$${(}^6$Li,p2n${)}^{95}$Ru and ${}_{}{}^{93}{}_{}{}^{}\mathrm{Nb}$${(}^7$Li,3n${)}^{97}$Ru reactions, using γ-γ coincidence, γ-W(θ), and pulsed-beam-γ measurements. Shell-model calculations of energy levels and B(E2) values for ${}_{}{}^{95}{}_{}{}^{}\mathrm{Ru}$ have been performed and compared with the experimentally observed levels and the measured ${\mathrm{}(21/2)\mathrm{}}^{+}$ and ${\mathrm{}(17/2)\mathrm{}}^{+}$ lifetimes. A collective ΔJ=2 band has been identified with the 1$h_{11/2}$ neutron state in ${}_{}{}^{97}{}_{}{}^{}\mathrm{Ru}$, and discussed in the context of the general nature of collectivity in nuclei outside the N=50 closed shell. No ΔJ=1 band associated with the 1$g_{9/2}$ neutron-hole intruder state was found in either of the N=51,53 Ru nuclei, as observed previously for the 1$g_{9/2}$ proton-hole intruder states in the Z=51 Sb and Z=53 I nuclei.

The inverse scattering formalism is applied to the case of the pion-helium system to obtain the real and imaginary parts of a local phenomenological potential from ${\pi }^{\mathrm{-}}$${\mathrm{-}}^4$He partial wave phase shifts at a fixed energy. The phase shifts and inelasticities for all partial waves up to angular momentum l=9 are extracted from the differential cross-section data by parametrizing the nuclear amplitude. The method has been tried for a number of incident pion energies between 51 and 110 MeV. The real and imaginary parts of the potential are seen to compare well with the commonly used pion-nucleus Laplacian potential.

The ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$${(}^3$He,t) reaction at 2 GeV is analyzed in the region of Δ-isobar production. Using the quasi-free mechanism in the framework of the distorted-wave Born approximation and the one-pion- and one-rho-exchange transition interaction, the measured angular distribution and the energy spectrum are reproduced well, both in magnitude and shape.

In the framework of a coupled-channel approach we construct a separable potential model for the low- and medium-energy antinucleon-nucleon interaction. The elastic part is derived from the meson-exchange Paris potential and represented in an on-shell and off-shell equivalent separable form. In analogy to microscopic theories the annihilation interaction is also described by a separable potential but with phenomenological form factors. Coulomb corrections to the hadronic interaction are taken into account rigorously. We present results for total, elastic, and charge-exchange cross sections and compare them to existing experimental data at low and medium energies. A first application of the model to the calculation of hadronic level shifts in antiprotonic hydrogen is reported.

We have investigated the possibility that a nucleus containing a single antinucleon (N¯) may exhibit some relatively long-lived excited states. Using N¯ optical potentials consistent with the available data on p¯-atom level shifts and/or low energy p¯-nucleus scattering, and calculating the complex eigenvalues of the Schrödinger equation, we find that the annihilation widths of strongly bound (non-Coulomb) N¯ states are generally large, as expected, of order Γ≊50–100 MeV. Some possible exceptions to this may occur when the N¯ is bound to a light nuclear core which is not spin and isospin saturated. We obtain cross section estimates for the formation of N¯ nuclei via the (p¯,p) and (p¯,n) reactions on nuclear targets with A=3, 4, and 16.

The momentum distributions of pions inelastically scattered from ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ and ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ were measured for incident energies of 350, 400, and 475 MeV. Pions were detected in a magnetic spectrometer at scattering angles of 60°, 90°, and 120°. The spectra show quasifree scattering from single nucleons along with a substantial component of lower momentum pions. The results are compared to a simple impulse approximation model, which accounts for the principal features of the data, but does not reproduce the low momentum tail even with the inclusion of multiple scattering.

The excitation functions for the pion-induced reactions ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$(${\pi }^{\pm }$,xN${)}^{18}$F, ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$(${\pi }^{\pm }$,xN${)}^{24}$Na, Si(${\pi }^{\pm }$,xN${)}^{18}$F, and Si(${\pi }^{\pm }$,xN${)}^{24}$Na have been determined for 50- to 390-MeV ${\pi }^{+}$ and 50- to 500-MeV ${\pi }^{\mathrm{-}}$. These excitation functions will enable experimenters to monitor high-intensity pion beams by activation of readily available high-purity Al foils or Si disks. The four excitation functions for ${}_{}{}^{18}{}_{}{}^{}\mathrm{F}$ production and the two for ${}_{}{}^{24}{}_{}{}^{}\mathrm{Na}$ production by ${\pi }^{+}$ show similar (3,3) resonance patterns. However, those for ${}_{}{}^{24}{}_{}{}^{}\mathrm{Na}$ production by ${\pi }^{\mathrm{-}}$ are strikingly different in that the cross sections remain large from the resonance energy on down. This feature is attributed to increasing contributions from ${\pi }^{\mathrm{-}}$ absorption and charge exchange with decreasing energy.

The five response functions which characterize the (e→,e’p) reaction are calculated in the distorted wave impulse approximation using a Dirac equation formulation of the nuclear bound and scattering wave functions and the usual free Dirac current operator. By evaluating the current matrix elements in momentum space, it is possible to recover the traditional Schrödinger dynamics and thus to study off-shell effects from the proton-nucleus final state interaction in both the relativistic and the nonrelativistic approaches. The longitudinal response function with relativistic effects included is reduced by about 20 percent relative to the nonrelativistic results. This is shown to be due to the Dirac final state interaction. Relativistic nuclear bound-state effects are found to be small in this reaction. The other four response functions show relativistic effects on the order of 5 to 10 percent. Off-shell effects are shown to be especially important in the interference response functions. A rough measure of the violation of current conservation in such calculations is presented and its implications for the calculations are discussed.

The independent isomer yield ratio for ${}_{}{}^{90}{}_{}{}^{}\mathrm{Rb}$ from thermal neutron fission of ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}$ has been measured by use of a new technique involving a pulsed reactor and an on-line mass spectrometer facility. The apparent isomer yield ratio was measured for several ion collection time intervals of different durations and extrapolated to zero collection time to eliminate interference from ${}_{}{}^{90}{}_{}{}^{}\mathrm{Kr}$ decay. The observed independent isomer yield ratio of 8.7±1.0 for ${(}^{90}$${\mathrm{Rb}}^{\mathrm{m}}$${)/\mathrm{}}^{90}$${\mathrm{Rb}}^{\mathrm{g}}$) is one of the largest ratios measured for a low energy fission process. However, a statistical model analysis shows that the average angular momentum (〈J〉=4.5) deduced from this isomer yield ratio is consistent with average angular momentum for several other products from low energy fission.

We have measured energies and angular distributions of three protons detected in coincidence following absorption of 228 MeV ${\pi }^{+}$ in carbon. The counters used were arranged in a geometry that should have enabled observation of the two-step process of proton knockout followed by quasi-deuteron absorption of the recoil pion. The absence of high energy protons emitted in the backward direction provides strong evidence that such a two-step process does not contribute appreciably to the total absorption cross section, and suggests that in fact the pion may scatter several times before finally being absorbed on a quasi-deuteron.

The pionic pair current is calculated from bag and constituent quark models which include a two-quark pion exchange potential. Except for form factors from the large Dirac-quark wave function, the result agrees with conventional nuclear theory. Gauge invariance is maintained. From the pion quark-pair and exchange currents inside a nucleon, a corresponding contribution to the proton and neutron magnetic moments is calculated.

The decays of ${}_{}{}^{101}{}_{}{}^{}\mathrm{Rh}_{}^{\mathrm{m}}{}_{}{}^{}$ and ${}_{}{}^{101}{}_{}{}^{}\mathrm{Rh}_{}^{\mathrm{g}}{}_{}{}^{}$ nuclides were studied by gamma-ray spectroscopy using both singles and coincidence spectra. The sources were obtained with the ${}_{}{}^{103}{}_{}{}^{}\mathrm{Rh}$(γ,2n${)}^{101}$${\mathrm{Rh}}^{\mathrm{m}}$,g reaction. Six transitions earlier attributed to the decays of these nuclides were not confirmed. The energies (keV) and the relative intensities for the observed gamma transitions following the ${}_{}{}^{101}{}_{}{}^{}\mathrm{Rh}_{}^{\mathrm{m}}{}_{}{}^{}$ decay are, respectively, 127.226(9), 0.79(2); 157.41(4), 0.280(5); 179.636(15), 0.660(15); 184.11(5), 0.193(3); 233.74(4), 0.2198(15); 238.27(4), 0.2505(17); 306.857(5), 100; 311.367(19), 0.0175(9); 417.86(5), 0.005; 545.117(7), 5.3(3). The energies and the relative intensities of the gamma transitions observed for the ${}_{}{}^{101}{}_{}{}^{}\mathrm{Rh}_{}^{\mathrm{g}}{}_{}{}^{}$ decay are the following: 110.94(12), 0.06(2); 127.226(9), 93.2(9); 184.22(13), 0.081(14); 198.01(3), 100; 295.01(3), 0.815(24); 325.23(3), 16.20(15); 422.19(8), 0.272(15). This work shows that only six excited levels are necessary to fit the observed data. Due to the simplification of the level scheme obtained in this work, the nuclear structure of the ${}_{}{}^{101}{}_{}{}^{}\mathrm{Ru}$ for low excitation energy can be described qualitatively with a quasi-particle-phonon model.

Compressed pellets of ${}_{}{}^{48}{}_{}{}^{}\mathrm{CaCO}_3^{}{}_{}{}^{}$ containing 3.71 g of ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$ were counted for 206 days in a well-type HPGe detector enclosed in a large NaI(Tl) detector. The cascade γ rays of 983.5, 1037.5, and 1312.1 keV in the ${\beta }^{\mathrm{-}}$ decay of 44-h ${}_{}{}^{48}{}_{}{}^{}\mathrm{Sc}$, which would follow the ${\beta }^{\mathrm{-}}$ decay of ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$, were searched for in the HPGe spectrum by requiring coincidences with summed γ rays in the NaI(Tl) detector. A 1900-2560-keV window on the NaI(Tl) included all three photopeak double sums. γγ coincidence efficiencies were determined with a calibrated ${}_{}{}^{48}{}_{}{}^{}\mathrm{Sc}$ source produced in the ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$(p,n) reaction at $E_{\mathrm{p}}$=12 MeV. By combining the upper limits on the intensities of the three γ rays, the half-life for ${}_{}{}^{48}{}_{}{}^{}\mathrm{Sc}$ was found to be $T_{1/2}$>6×${10}^{18}$ yr (95% confidence). For the $0^{+}$→$5^{+}$ unique fourth-forbidden ${\beta }^{\mathrm{-}}$ branch of ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$ to the 131-keV first-excited state of ${}_{}{}^{48}{}_{}{}^{}\mathrm{Sc}$, log$f_0$t>24.3. Our experimental half-life limit is a factor of 300 longer than a previous result but is still two orders of magnitude shorter than a recent theoretical estimate.

The decay rate of the 2ν double beta decay is calculated. The effects of pairing, static quadrupole deformation, spin-isospin polarization, and the ${\Delta }_{33}$ isobar admixtures on the nuclear matrix elements are studied and the relation of the 2ν ββ rate and the ${\beta }^{\mathrm{-}}$ and ${\beta }^{+}$ strength is stressed. In agreement with other calculations, we predict a faster decay rate than has been observed experimentally in ${}_{}{}^{82}{}_{}{}^{}\mathrm{Se}$, ${}_{}{}^{130}{}_{}{}^{}\mathrm{Te}$, and ${}_{}{}^{150}{}_{}{}^{}\mathrm{Nd}$.

The T=0 coordinate-space linear response random-phase approximation method is generalized to finite temperatures. Continuum effects are included through the temperature single-particle Green’s functions. The method is utilized to investigate the temperature dependence of isovector electric dipole excitations in ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$. The experimentally observed downward shift of the giant resonance and the spreading of the dipole strength as temperature increases are clearly reflected in the calculated cross sections. The present approach to the temperature dependent random-phase approximation method offers a remedy to some of the limitations inherent in other existing formulations of the theory.

We demonstrate, using an energy-dependent separable-potential model, that the triton binding energy is sensitive to variations of the singlet effective range, $r_{\mathrm{nn}}$, for fixed off-shell and intermediate-energy phase-shift constraints.

An increasing amount of experimental data indicates that spin-flip quadrupole transitions exhibit quenching effects similar to those reported earlier in (p,n) reactions involving l=0 and l=1 transitions. We present here two model calculations suggesting that the E2 spin-flip transitions are more affected than their M1 and M3 counterparts by the tensor and spin-orbit components of the nuclear force and should exhibit the largest quenching. We also review the experimental evidence corroborating our observations.

The nuclear level density ρ(U,I) is derived from an equation of state, without reference to the Fermi gas model. If the yrast line backbends, then the effective level density parameter $a_{\mathrm{eff}}$ must be spin dependent at low temperatures. The spin dependent components of $a_{\mathrm{eff}}$ renormalize the spin cutoff factor σ.