It is shown that a recent analysis of pion photoproduction is inconsistent with the fundamental requirements of current conservation. For a monopole vertex function, the analysis should lead to a value Λ≃680 MeV rather than 1000 MeV as claimed.

In reply to the preceding Comment by Picciotto, it is argued that dual model factorization is not inconsistent with gauge invariance and that the ππγ vertex function, with one pion being the only off-mass-shell particle, is expected to exhibit dynamical structure when embedded in the one-pion-exchange approximation to the four-point function γN→πN.

Measurements of $A_{\mathrm{LL}}$ between 500 and 800 MeV and spin dependent cross sections derived from these measurements are presented for the reaction pp→πd at c.m. angles ${\theta }_{\pi }^{\mathrm{*}}$ of 50°, 70°, and 90°. Angular distributions for $A_{\mathrm{SL}}$ are also presented for energies 500, 650, and 800 MeV. These are the first measurements of spin-correlation parameters in this channel above 590 MeV, and are in substantial disagreement with theoretical predictions of the triplet amplitudes above 600 MeV.

We present measurements of the inclusive ${\pi }^{\pm }$ momentum distributions and total pion production cross sections for 330, 400, and 500 MeV protons incident on ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$. The ${\pi }^{+}$/${\pi }^{\mathrm{-}}$ cross section ratio is seen to increase sharply with decreasing projectile energy for the light nucleus. Comparisons are also presented of the projectile energy systematics of data and intranuclear cascade calculations in the intermediate energy region.

The Boltzmann master equation is used to predict linear momentum transfer for reactions of ${}_{}{}^{60}{}_{}{}^{}\mathrm{Ni}$ with ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ at lab energies of 8.8 to 100 MeV/nucleon. Results are in excellent agreement with experimental measurements at ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ energies up to 19.6 MeV/nucleon.

Shape evolution in the I≥30ħ high-spin states of ${}_{}{}^{144–150}{}_{}{}^{}\mathrm{Gd}$, ${}_{}{}^{150–156}{}_{}{}^{}\mathrm{Dy}$, ${}_{}{}^{152–158}{}_{}{}^{}\mathrm{Er}$, and ${}_{}{}^{154–160}{}_{}{}^{}\mathrm{Yb}$ is predicted theoretically within the cranking approximation using the generalized Strutinsky method. A comparison with available experimental data is provided.

Motivated by a recent experiment, the differential cross section and the tensor analyzing power $T_{20}$ for elastic pd backward scattering is calculated in a microscopic model, which includes both the conventional one-nucleon exchange mechanism and rescattering contributions from the Δ(1236) resonance. If supplemented by multiple scattering corrections, the model qualitatively accounts for the large negative values of $T_{20}$ for deuteron energies up to 2.3 GeV; however, it fails to reproduce the dip structures observed experimentally. Possible extensions of the model are briefly discussed.

In this work we employ the hyperspherical harmonics formalism to calculate the moments of the photoeffect of the alpha particle. The grand orbital quantum number is increased until well-converged results are obtained. The adiabatic approximation is used to solve the coupled differential equations. The calculations are performed for a central N-N potential with Serber exchange. Lastly, the moments are inverted to obtain the photodisintegration cross section. Comparisons with experimental observations are presented.

The effect of two-body charge density due to one-pion exchange on the triton photodisintegration sum rules has been investigated. The inclusion of the two-body charge density modifies the Siegert form of the dipole operator, resulting in a change in the enhancement factor and the bremsstrahlung-weighted cross section. The expressions obtained for the integrated and the bremsstrahlung-weighted cross sections are quite general, as all the two- and three-body intermediate states have been included. The numerical work is carried out employing a variational wave function and two-body interactions having only central and tensor components. It is found that the change in the enhancement factor is quite significant (∼16%) for the pseudoscalar coupling and only about 2% with the pseudovector coupling, and can provide information about the nuclear interaction and theories of meson exchange contributions to the triton photodisintegration sum rules.

The excitation functions for the α particles and protons from the reactions ${}_{}{}^{55}{}_{}{}^{}\mathrm{Mn}$(p,p${)}^{55}$Mn and ${}_{}{}^{55}{}_{}{}^{}\mathrm{Mn}$(p,α${)}^{52}$Cr were measured from $E_{\mathrm{p}=5.8\mathrm{}}$ to 7.0 MeV at ${\theta }_{\mathrm{lab}}$=90°, 125°, and 160°. The cross sections were analyzed by the channel cross correlation function, the autocorrelation function, and the statistical compound nuclear theory of Feshbach to determine the number of correlating channels $n_d$, the average total level width 〈${\Gamma }_{\mu }$〉, and the ratio 〈${\Gamma }_{\mu }$〉/D. With these values, the theoretical intermediate width 〈${\Gamma }_d$↑〉 was calculated to be 27±11.7 keV, which was consistent with the experimental result 36±8 keV within the errors. The ratio $n_d$($n_d$-1)/$n^2$ was determined to be 0.63±0.16, which was also in agreement with the theoretical prediction (2D/π〈${\Gamma }_{\mu }$${〉}^{1/2}$=0.40±0.0 9, within the error.

The fragmentation of nuclear systems, formed in proton- and heavy-ion-induced reactions in a wide energy range, is examined. The dependence of the fragment production cross section on the incident energy and on the temperature of the emitting source is compared to predictions of a theory of condensation. We find many instances where the fragmentation instability can be explained by and may be attributed to a liquid-gas phase transition. Our analysis suggests the occurrence of instabilities at a critical temperature of approximately 11 to 12 MeV, in accord with several theoretical predictions. Conventional nuclear effects, such as Coulomb barrier penetration, cannot fully describe the observed phenomena.

Recently we have seen a series of highly successful fits to data for nucleon-nucleus scattering which are based upon the use of the Dirac equation. In the phenomenological analysis the potential in the Dirac equation is usually limited to two terms, a (Lorentz) scalar and vector potential. In a recent work we have shown that there are eight scalar invariants that are needed to fully specify the relativistic interaction of an off-shell nucleon with an on-shell, spin zero nucleus. It appears that the phenomenological potentials are effective potentials in the sense that their values need to be adjusted to compensate for the use of a highly simplified phenomenological form. In this work we present calculations of the complete potential, including estimates of the eight terms noted above. Our preliminary results indicate that the values of the phenomenological potentials can be reproduced in a microscopic calculation and bear out our ideas concerning the significance of the phenomenological potentials. It is found that if one wishes to obtain the correct value for the spin-orbit potential strength, for example, in a microscopic calculation, one must consider the optical potential in its most general form. At projectile energies greater than 300 or 400 MeV we expect that only two of the eight terms noted above will be important and therefore the relativistic impulse approximation will provide a satisfactory basis for calculating the optical potential.

Structure in the spectra of neutrons emitted from iron upon bombardment with 14.6 MeV neutrons has been investigated and explained in terms of excitation of levels in ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}$. The energies of scattered neutrons have been measured by the time-of-flight technique based on the associated particle method. The observed excitations have been correlated with the reported levels in a satisfactory manner. Evidence for new excitations at 8.8±0.2, 9.8±0.1, 10.2±0.1, 12.44±0.03, and 12.52±0.03 MeV has been obtained. The excitation of possible components of the M1 giant resonance in ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}$ is discussed.

Measurements have been carried out for 14.6 MeV neutrons incident on natural iron using the associated particle time-of-flight technique. The elastic differential and neutron emission cross sections have been measured in the energy range 4.5–13.5 MeV and laboratory angular range 30°–130°. Monte Carlo simulation has been used for multiple scattering and flux attenuation corrections. A value of 477±48 mb has been obtained for the neutron emission cross section in the energy range 4.5–13.5 MeV. The present measurements have been compared with previous measurements and model calculations.

Low-lying positive parity levels of the isotopes in natural cadmium were Coulomb excited with 2.7–4.2 MeV protons. Eight levels of ${}_{}{}^{111}{}_{}{}^{}\mathrm{Cd}$ up to 1130.4 keV and four levels of ${}_{}{}^{113}{}_{}{}^{}\mathrm{Cd}$ up to 680.5 keV excitation energy, and the first $2^{+}$ states in even-even isotopes ${(}^{110}$,112,114,116Cd) were excited. A 50 ${\mathrm{cm}}^3$ Ge(Li) detector was used to measure the deexcitation gamma-ray yields. The 1130.4 keV level in ${}_{}{}^{111}{}_{}{}^{}\mathrm{Cd}$ had not been investigated earlier through Coulomb excitation. Also the 245.4, 700, 754.9, 855.6, and 1020.7 keV levels in ${}_{}{}^{111}{}_{}{}^{}\mathrm{Cd}$, and the 316.1 keV level in ${}_{}{}^{113}{}_{}{}^{}\mathrm{Cd}$ were Coulomb excited with protons for the first time. The reduced E2 transition probabilities B(E2), and partial half-lives $T_{1/2}$ (E2), for various levels were determined. The gamma-ray angular distributions were analyzed to deduce the E2/M1 mixing ratios (δ) for various transitions from the levels in ${}_{}{}^{111}{}_{}{}^{}$,113Cd. The 700, 754.9, 855.6, and 1020.7 keV levels in ${}_{}{}^{111}{}_{}{}^{}\mathrm{Cd}$, and the 680.5 keV level in ${}_{}{}^{113}{}_{}{}^{}\mathrm{Cd}$ have been assigned a spin value of ${\mathrm{}(3/2)\mathrm{}}^{+}$, while the 1130.4 keV level in ${}_{}{}^{111}{}_{}{}^{}\mathrm{Cd}$ has been assigned a spin of ${\mathrm{}(5/2)\mathrm{}}^{+}$. The results have been compared with existing theoretical and experimental data in the literature.

The measured (p,p) and (p,n) excitation functions for ${}_{}{}^{92}{}_{}{}^{}$,94,96Zr and ${}_{}{}^{95}{}_{}{}^{}$,98,100Mo were fitted in the energy range 2<$E_{\mathrm{p}}$<7 MeV using a standard optical model potential with an energy dependent proton absorptive potential. The volume integral of the proton absorptive potential shows strong A dependence at low proton energy and tends to a common value of 100 MeV ${\mathrm{fm}}^3$ for all isotopes studied as the proton bombarding energy is increased toward 15 MeV. This result is consistent with results from analyses at higher energies.

The stripping reaction (α,t) at 80 MeV incident energy has been used to study the proton-particle response function on ${}_{}{}^{116}{}_{}{}^{}\mathrm{Sn}$, ${}_{}{}^{144}{}_{}{}^{}\mathrm{Sm}$, and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ target nuclei up to 22 MeV excitation energy. Rather complete spectroscopic information has been obtained on the low-lying proton states (0–3 MeV) through angular distribution measurements and standard distorted wave Born approximation analysis. Strong transitions to high-lying proton states located between 5 and 12 MeV excitation energy in ${}_{}{}^{145}{}_{}{}^{}\mathrm{Eu}$ and ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}$ are observed whereas the spectrum from the ${}_{}{}^{116}{}_{}{}^{}(\mathit{\alpha }$,t) reaction displays only broad, weak enhancement of cross sections at high excitation. These transitions appear as broad bumps superimposed on a continuous background for which a qualitative analysis within the framework of the breakup model has been attempted. The excitation energies, angular distributions, and strengths of these high-lying transitions suggest that they arise from proton stripping to high-spin outer subshells, e.g., 1h(9/2) and 1i(13/2) in ${}_{}{}^{145}{}_{}{}^{}\mathrm{Eu}$, and 1i(11/2) and 1j(15/2) in ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}$. A distorted-wave Born approximation analysis using resonant form factors for the states located above the proton threshold has been carried out. The deduced proton strength distributions are compared with the predictions from the quasiparticle-phonon and single-particle vibration coupling nuclear models. Around 12–14 MeV excitation energy, narrow peaks corresponding to the population of the isobaric analog states in ${}_{}{}^{117}{}_{}{}^{}\mathrm{Sb}$ and ${}_{}{}^{145}{}_{}{}^{}\mathrm{Eu}$ are also observed. Our results are compared to the known spectroscopic properties of the corresponding parent states in ${}_{}{}^{117}{}_{}{}^{}\mathrm{Sn}$ and ${}_{}{}^{145}{}_{}{}^{}\mathrm{Sm}$.

Photoneutron energy spectra from the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}(\gamma ,{\mathrm{n}}_0){}_{}{}^{15}{}_{}{}^{}\mathrm{O}$ reaction were measured as functions of laboratory angle over a range of excitation energies from 30 to 35 MeV. Angular distribution Legendre-polynomial coefficients were extracted up to third order as functions of excitation energy. Nonzero values of the coefficients $a_1 (+0.25\mathrm{}\pm 0.02)$ and $a_3 (-0.2\mathrm{}\pm 0.02)$ were observed over the energy region explored, indicating interference between states of opposite parity. These values can be accounted for in a simple model incorporating electric quadrupole absorption strength decaying via the ground-state photoneutron channel. When combined with the previously-determined amplitude ratio for the $E1$ $p\to s$ and $p\to d$ single-particle transitions, the present results suggest that about 4% of the isovector energy-weighted sum rule is found in the ($\gamma$,${\mathrm{n}}_0$) channel in the energy range studied. The value of the ($\gamma$,${\mathrm{n}}_0$) cross section was found to vary from 1.5±0.1 mb at $E_x=30\mathrm{}$ MeV to 0.8±0.1 mb at 35 MeV. The average magnitude of the $E2\mathrm{}$ contribution to this cross section was estimated to be 0.05±0.02 mb. This is in reasonable agreement with a recent continuum randomphase approximation shell model calculation, but is in disagreement with a previous measurement.