The single-particle potential in nuclear matter is calculated microscopically for several Hamiltonians for densities ranging from 0.1 to 0.5 ${\mathrm{fm}}^{\mathrm{-}3}$. These Hamiltonians include nucleon-nucleon potentials fit to scattering data and three-nucleon potentials fit to the binding energies of few-body nuclei and saturation properties of nuclear matter. The single-particle potential is a key ingredient in Boltzmann-Uehling-Uhlenbeck simulations of heavy-ion collisions. Parametrizations of the density and momentum dependence of the single-particle potential that may be useful in such simulations are discussed and compared to phenomenological prescriptions currently in use.

Within the quasiparticle random phase approximation, we compare two-neutrino double beta decay amplitudes calculated with zero-range and finite-range nucleon-nucleon interactions. We find that if, as is customary, interaction constants are fit to energies of giant Gamow-Teller states and to ${\beta }^{+}$ strengths, the two interactions lead to very similar two-neutrino double beta amplitudes. We discuss additional approximations related to the inclusion (or neglect) of the Hartree-Fock part of the pairing interaction, and to the treatment of differences between the initial and final nuclear ground states. The numerical values of the amplitudes depend more on the way these approximations are made than on the form of the nucleon-nucleon force.

The new form of the Siegert theorem given recently by Mosconi and Ricci is shown to be incorrect. Furthermore, the use of the Siegert theorem in the work of Partovi is shown to be essentially correct in contrast to the critique raised by others.

Our derivation of Siegert’s theorem is reexamined with conclusions in agreement with the preceding Comment. A deuteron photodisintegration model which allows a numerical check of the theorem is presented.

The energy dependence of cross sections for inelastic pion scattering to the $\Delta S=\Delta T=\Delta J=1\mathrm{}$ transition at 15.11 MeV in ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ is found to map very closely the $\Delta S=\Delta T=\Delta J=1\mathrm{}\pi$-nucleon scattering cross sections at beam energies from 50 to 295 MeV. This free $\pi$-nucleon energy dependence is due to the prominent ${\Delta }_{\frac{3}{2},\frac{3}{2}}$ resonance, corresponding to the first excited nucleon state, which is mirrored in the $\pi$-nucleus system with little alteration.

Low-lying levels of the nucleus ${}_{}{}^{142}{}_{}{}^{}\mathrm{Ce}$ have been studied by Coulomb excitation with ${}_{}{}^4{}_{}{}^{}\mathrm{He}$, ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, and ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ projectiles to determine various $B\left(E\lambda \right)$ values and the static quadrupole moment $Q\left(2_1^{+}\right)$. Excellent agreement is found between the observed properties and predictions made using the U(5) limit of the proton-neutron interacting boson model. The results strongly support the contention that the $2_3^{+}$, 2.004-MeV level has mixed proton-neutron symmetry. Combining the present measurement for $B(E2;0_1^{+}\to 2_3^{+})$ of $0.070\pm 0.011 e^2{b}^2$ with known branching and mixing ratios gives a substantial $M1\mathrm{}$ strength of $(0.26\mathrm{}\pm 0.05){\mu }_N^2$ for the $2_3^{+}$ → $2_1^{+}$ transition.

Isotope shift measurements on even-$A$ Pt isotopes have been obtained from $A=186\mathrm{}$ to $A=198\mathrm{}$. Charge radius differences have been extracted, and are compared to constrained Hartree-Fock plus BCS calculations. A possible shape transition between ${}_{}{}^{186}{}_{}{}^{}\mathrm{Pt}$ and ${}_{}{}^{188}{}_{}{}^{}\mathrm{Pt}$ is discussed.

A new technique for approximating solutions of the two-body Bethe-Salpeter equation is presented. Coupled equations for the relative energy dependence and the relative three-momentum dependence of the relativistic $T$ matrix are derived. These equations are solved self-consistently for the Wick-rotated $T$ matrix in a simple model problem and the numerical results are compared with exact as well as usual three-dimensional reduction results.

The role of three-body exchange currents is investigated in the two-body photodisintegration of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$.

The ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$(t,α) reaction has been used to populate states in ${}_{}{}^8{}_{}{}^{}\mathrm{Li}$. Angular distributions were measured for four low-lying narrow states, and distorted-wave Born approximation calculations (including coupled channels) were used to analyze the data. The results are compared with results of a ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$(d${,}^3$He) reaction and with Cohen-Kurath shell-model predictions.

The absolute total cross section for the ${}_{}{}^4{}_{}{}^{}\mathrm{He}$(γ,p${)}^3$H reaction has been measured in the γ-ray energy region between 28.6 and 58.1 MeV with a monochromatic photon beam and a nearly 4π proton detector. The comparison of our results with the most recent data on the ${}_{}{}^4{}_{}{}^{}\mathrm{He}$(γ,n${)}^3$He total cross section provides a mean value of ${\mathit{R}}_{\gamma }$=σ(γ,p)/σ(γ,n) =1.01±0.06 between 28.6 and 42.4 MeV and tends to exclude a strong isospin mixing in the ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ due to charge symmetry breaking of the nuclear force.

The photon spectrum from radiative absorption of negative muons in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ has been measured with a high-resolution pair spectrometer. The integrated branching ratio for photons with energies greater than 57 MeV relative to the total muon absorption rate is (3.8±0.4)×${10}^{\mathrm{-}5}$. The data are consistent with nuclear model calculations for a value of the induced pseudoscalar coupling in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ of $g_P$/$g_A$=13.5±1.5.

Excitation functions for the ${}_{}{}^{27}{}_{}{}^{}(\mathit{p}$,γ${)}^{28}$Si reaction have been obtained over the energy range $E_p$=0.5–1.8 MeV. Capture was studied to the ground state ${(0\mathrm{}}^{+}$) and the first excited state ${(2\mathrm{}}^{+}$) at $E_x$=1779 keV. Detailed angular distributions were obtained in the energy region near $E_p$=850, 1060, 1140, and 1623 keV. The data are compared with direct capture calculations which employ a real Woods-Saxon well in both the entrance channel and the final state. The analysis of the data provides no evidence for the presence of a significant semidirect contribution.

Convergence properties of the pseudostate method in the d+α system are investigated with respect to the number of deuteron Gaussian basis functions and the number of pseudo-inelastic configurations. Results indicate that the deuteron specific distortion effect can be well described by using about 10 to 15 Gaussian basis functions to generate deuteron wave functions in the ground and pseudo-excited states. Also, it is found that, for the ground-state energy of ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ and for d+α scattering in the very low energy region, only deuteron pseudo-excited states with excitation energies less than about 60 MeV need to be included. In addition, the investigation shows that the calculated total reaction cross sections are rather severely underestimated, indicating that even more cluster configurations must be introduced into the resonating-group formulation in order to obtain a satisfactory explanation of all the important features of the six-nucleon system.

The ${}_{}{}^{22}{}_{}{}^{}\mathrm{Na}$(n,$p_0$), (n,$p_1$), (n,${\alpha }_0$), (n,${\alpha }_1$), and (n,${\alpha }_2$) cross sections have been measured at thermal neutron energy. In addition, the $p_0$ and $p_1$ cross sections have been measured from thermal energy to 420 eV and 35 keV, respectively. These new data were used to discern the structure of ${}_{}{}^{23}{}_{}{}^{}\mathrm{Na}$ near the neutron threshold. In particular, it was found that a (${\mathrm{}(7/2)\mathrm{}}^{+}$ resonance dominates the $p_1$ cross section but contributes very little to the $p_0$ cross section. The $p_0$, and also most probably the (n,${\alpha }_0$) cross sections, are instead dominated by a separate (${\mathrm{}(5/2)\mathrm{}}^{+}$ resonance. The ${}_{}{}^{22}{}_{}{}^{}\mathrm{Na}$(n,p${)}^{22}$Ne astrophysical reaction rate, $N_A$〈σv〉, was calculated using our new data and compared to published theoretical rates used in previous nucleosynthesis calculations. It was found that the theoretical rates are approximately a factor of 5 to 10 different from the experimental one at most temperatures measured. We discuss the possible implications of this difference on nucleosynthesis calculations for ${}_{}{}^{22}{}_{}{}^{}\mathrm{Na}$ and ${}_{}{}^{22}{}_{}{}^{}\mathrm{Ne}$.

The ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$(p,d${)}^{26}$Al reaction has been studied at $E_p$=35 MeV with high resolution to populate known $5^{\mathrm{-}}$ and $6^{\mathrm{-}}$ stretched states of $d_{5/2}$-hole–$f_{7/2}$-particle structure, and to obtain the weak spectroscopic factors. These are compared to results also obtained for the ${}_{}{}^{26}{}_{}{}^{}\mathrm{Mg}$(p,d${)}^{25}$Mg and ${}_{}{}^{26}{}_{}{}^{}\mathrm{Mg}$${(}^3$He,α${)}^{25}$Mg reactions to known ${(7/2\mathrm{}}^{\mathrm{-}}$ states. An analysis of these results in the Nilsson scheme exposes the structure of the $6^{\mathrm{-}}$ stretched states and offers an understanding of the fragmentation of M6 stretched transition strength in ${}_{}{}^{26}{}_{}{}^{}\mathrm{Mg}$, as seen by electron scattering. This work is part of a consistent study of many nuclear reactions to stretched states in mass 26, to serve as a test case for these important single-particle modes.

Angular distributions of the vector analyzing powers for the ${}_{}{}^3{}_{}{}^{}\mathrm{H}$${(}^3$He${,}^2$H${)}^4$He reaction have been measured over the incident energy range 18–33 MeV. The measurements centered about 18 MeV display a deviation from the antisymmetric shape expected from isospin symmetry. Concentrating on the explanation of the 90° analyzing powers, we report the results of a distorted-wave Born approximation (DWBA) analysis which includes the direct and exchange processes and the spin-orbit potential. It is shown that the anomalous behavior of the 90° vector analyzing powers can be largely explained by the effect of a single F-wave potential resonance which leads to the magnification of the short-range differences between the ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ and ${}_{}{}^3{}_{}{}^{}\mathrm{H}$ wave functions.

Ratios of (t,p) transfer intensities to $0^{+}$ states in the cadmium isotopes have been analyzed using a three-state mixing model. The data allows determination of the degree of mixing of the rotational (intruder) state into the zero-phonon and two-phonon $0^{+}$ states. The three lowest $0^{+}$ states are found to be relatively pure and the intruder state lies above the two-phonon state in the heavier isotopes.

Angular distributions of the analyzing power $A_y$(θ) have been measured for neutron elastic scattering and for neutron inelastic scattering to the first $2_1^{+}$ states of ${}_{}{}^{54}{}_{}{}^{}$,56Fe and ${}_{}{}^{58.60}{}_{}{}^{}\mathrm{Ni}$ at 10 MeV, and for ${}_{}{}^{54}{}_{}{}^{}\mathrm{Fe}$ and ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$ at 14 and 17 MeV. The differential cross sections σ(θ) for the same processes were measured at 17 MeV for ${}_{}{}^{54}{}_{}{}^{}\mathrm{Fe}$ and ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$. These measurements have been combined with other measurements of σ(θ) and $A_y$(θ) and also with total cross sections to form a sizable data set for incident neutron energies up to 80 MeV. This data set has been described in the context of the coupled channels formalism to determine the energy dependences of the various terms of the deformed optical potential. Some emphasis was placed on investigating the magnitude of the deformation parameter ${\beta }_{\mathrm{so}}$ of the neutron spin-orbit potential and the possibility that it might be energy dependent.

The α${+}^{40}$Ca elastic scattering cross sections in the energy range from 29.0 to 61.0 MeV are shown to be well reproduced by the resonating-group method by introducing a phenomenological imaginary potential. The local potential equivalent to the nonlocal potential of the resonating-group method is found to be very close to the optical potential of Delbar et al. which fits the scattering data well in a wide energy range. Since the optical potential of Delbar et al. is the so-called unique optical potential which is free from the discrete ambiguity, this result means that the resonating-group method is powerful and reliable for the study of the internucleus interaction. By calculating the bound and quasibound level spectra by the same α${+}^{40}$Ca resonating-group method, it is found that the lowest positive parity rotational band is located near the observed ground rotational band of ${}_{}{}^{44}{}_{}{}^{}\mathrm{Ti}$. In addition, when we use other effective two-nucleon forces so as to locate the calculated lowest $0^{+}$ state near the observed excited $0^{+}$ state with the excitation energy 8.54 or 11.2 MeV, which has large α strength, the fitting of the elastic scattering data by the resonating-group method is found to be very bad. These results force us to regard that the structure of the ${}_{}{}^{44}{}_{}{}^{}\mathrm{Ti}$ ground band as containing a large amount of α${+}^{40}$Ca clustering component. However our present resonating-group method predicts the appearance of the negative parity rotational band with its bandhead $1^{\mathrm{-}}$ state below the excitation energy 10 MeV although there have been reported no such experimental indications at all of this.