Using a fixed configuration deformed Hartree-Fock method, we examine possible candidates for shape isomer states in several N=Z nuclei ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$, ${}_{}{}^{44}{}_{}{}^{}\mathrm{Ti}$, ${}_{}{}^{48}{}_{}{}^{}\mathrm{Cr}$, ${}_{}{}^{52}{}_{}{}^{}\mathrm{Fe}$, and ${}_{}{}^{56}{}_{}{}^{}\mathrm{Ni}$. We treat larger deformations than we did before and thus have to excite more particles and include more major shells. We have two criteria for a stable shape isomer. We find that in all the cases considered there exist stable, highly deformed states which satisfy both the conditions. One example is the 12-particle–12-hole states in ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ with ${\mathrm{\beta }}_0$=0.965. We consider the possibility of associating some of these shape isomers with molecular resonances obtained in heavy ion reactions such as ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$${+}^{24}$Mg ${(}^{48}$${\mathrm{Cr}}^{\mathrm{*}}$) or ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$${+}^{28}$Si ${(}^{56}$${\mathrm{Ni}}^{\mathrm{*}}$).

Results are presented from a search for high-energy gamma rays (${\mathit{E}}_{\gamma }$>140 MeV) resulting from the decay of the delta resonance produced in heavy-ion collisions. The energy spectrum of gamma rays in the energy range 15<${\mathit{E}}_{\gamma }$<180 MeV was measured at a laboratory angle of 90° for the reaction ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$+Zn. The incident beam energy was E/A=75 MeV. The energy spectrum in the region 50<${\mathit{E}}_{\gamma }$<180 MeV is exponential with an inverse slope parameter of 26 MeV. There is no indication of an enhancement in the spectrum above 140 MeV due to the decay of the delta resonance.

New measurements of differential elastic neutron scattering for ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}$ at energies between 7.5 and 24.0 MeV are presented along with new measurements of ${\mathrm{\sigma }}_{\mathit{T}}$ up to 60 MeV. These data, taken together with earlier measurements at lower energy, provide a very large data set for testing and extending the dispersive optical-model analysis. The dispersion correction to the optical model has been obtained from the scattering and total cross-section data. The potential is extrapolated to negative energy for comparison with bound-state properties. A very good description of all of the data is obtained from -20 to +60 MeV. The present analysis suggests somewhat less depletion of the Fermi sea in this mass region than has been obtained from electron-scattering data and from other recent treatments of the dispersion correction to the optical model.

Velocity spectra of thirteen different fragment species from ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ to ${}_{}{}^{15}{}_{}{}^{}\mathrm{N}$ at seven angles from 15° to 83° and of neutrons in coincidence with them have been determined from ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$+Ag collisions at 35 MeV/nucleon. The velocity spectra of the fragments show contributions from quasielastic and deep-inelastic processes. The quasielastic part of each spectrum was fitted with an empirical model. For each fragment species, the deep-inelastic part at each of the seven angles was simultaneously fitted with a single moving source. The parameters T for source temperature and E/A, corresponding to source velocity, were approximately independent of fragment species and had average values of 12.8 and 3.9 MeV, respectively. Many coincidence neutron spectra were created off line by selecting gates having various fragment species, angles, and velocity intervals. The neutron spectra at seven or eight angles with a given gate were simultaneously fitted with two moving sources. The source parameters had little dependence on the gate. The average values of T and E/A for one source, an intermediate rapidity source, were 10.4 MeV and 10.7 MeV/nucleon, respectively. The other source, a slowly moving targetlike source, had T and E/A in the ranges 2.0–3.6 MeV and 0.1–0.3 MeV/nucleon, respectively. Since neither of these neutron sources has the velocity of the fragment source, the actual origin of the deep-inelastic fragment may be a nonequilibrium process such as the stripping-pickup process.

The angular distributions of cross sections for the reaction ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$${(}^3$He${,}^4$He${)}^{12}$C leading to ground state and first excited 4.44 MeV, $2^{+}$ state of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ have been measured at sub-Coulomb energies of ${\mathit{E}}_{\mathrm{c}.\mathrm{m}.\mathrm{}}$=1.20 and 1.05 MeV. The angular distributions are asymmetric with respect to 90° and anisotropies are also found to be much larger than those expected from compound nuclear processes. Analyses of the data, with assumptions of direct transfer processes, by exact finite range distorted wave Born approximation calculations show the presence of interference of two modes of direct transfer mechanisms of neutron transfer and ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$ cluster transfer from the target ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ to the projectile ${}_{}{}^3{}_{}{}^{}\mathrm{He}$. These direct transfer calculations are in good agreement with the angular distributions and yield the value of the ratio of three nucleon spectroscopic strengths of first excited state to ground state of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ in good agreement with the value predicted from structure calculations.

An existing model of alpha-particle-induced reactions has been extended to include fission competition. Forty-six excitation functions from nine target nuclei at incident energies to 50 MeV have been calculated and compared to experimental data taken from the literature of the last 35 years. In particular, it is shown that specific modes of interaction of the alpha particle are responsible for the features of individual excitation functions. A simple fission barrier characterized only by its height is shown to suffice in reproducing the fission-evaporation competition.

Total cross sections for the pion single-charge-exchange reaction ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(${\mathrm{\pi }}^{+}$,${\mathrm{\pi }}^0$${)}^{12}$N (ground state) were measured at 116, 160, 180, 200, 230, and 291 MeV with a fast activation technique. The excitation function for this nonanalog, spin-flip transition was found to be flat over this energy region that includes the (3,3) resonance. Good agreement is noted between these measurements and the estimated cross sections obtained from pion inelastic scattering measurements for the analog reaction ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(${\mathrm{\pi }}^{+}$,${\mathrm{\pi }}^{+}$’${)}^{12}$${\mathrm{C}}^{\mathrm{*}}$ ($1^{+}$,T=1,${\mathit{E}}_{\mathit{x}}$=15.1 MeV) for all energies except 230 MeV. Distorted-wave impulse-approximation calculations in the Δ-hole formalism do not reproduce the trend of the data.

Inclusive neutron spectra were measured at 0°, 4°, 8°, 15°, 30°, and 42° from Nb-Nb and Au-Au collisions at 800 MeV/nucleon. A peak that originates from neutron evaporation from the projectile appears in the spectra at angles out to 8°. The shapes and magnitudes of the spectra are compared with those calculated from models of nucleus-nucleus collisions. The differential cross sections for Au-Au collisions are about four times those for Nb-Nb collisions. The predictions of the Vlasov-Uehling-Uhlenbeck (VUU) and QMD theories agree with the angular distributions of the differential cross sections except at small angles; the VUU prediction overestimates the angular distributions from a few degrees to about 20°, whereas the QMD prediction underestimates the angular distributions below 8°. The Firestreak model overestimates the angular distribution for Nb-Nb collisions and underestimates it for Au-Au collisions. Also, the VUU and QMD models agree with the measured double-differential cross sections in more angular and energy regions than the Firestreak and intranuclear cascade models; however, none of the models can account for the peaks at small angles (θ≤15°).

Inelastic-electron-scattering cross sections have been measured for the first three excitations in ${}_{}{}^{89}{}_{}{}^{}\mathrm{Y}$ at forward angles for momentum transfers of 1.25<q<3.01 ${\mathrm{fm}}^{\mathrm{-}1}$ and at 180° for 0.72<q<2.67 ${\mathrm{fm}}^{\mathrm{-}1}$. Transition charge and current densities extracted in a Fourier-Bessel analysis of all existing cross sections show considerable departures from the single-particle model. The inclusion of core polarization from the operator renormalization approximation for shell models gives good agreement with experimental results.

Fission cross sections and angular distributions have been measured for the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$${+}^{232}$Th reaction at the bombarding energies from 76 to 86 MeV. The fission excitation function is rather well reproduced on the basis of the Wong model. However, the model that reproduces the enhancement observed in the sub-barrier fusion excitation function fails to account for the experimental anisotropies. It is found that the observed anisotropy is much larger than expected, and as a function of center-of-mass energy it exhibits a peak around 76 MeV with a width (FWHM) of 3.7±0.5 MeV. A comparison with our previous data of ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}$${+}^{232}$Th reaction reveals that the anomaly is strongly related to the nuclear structure property of the projectile nucleus.

The calculation of transmission coefficients for emitted particles is fundamental to applications of the statistical evaporation model for the decay of the compound nucleus. In this work we compare the usual type of optical-model calculation of transmission coefficients for neutron, proton, deuteron, triton, and alpha particles with corresponding ingoing-wave boundary-condition calculations. In the latter case the transmission coefficients simply give the probability for transmission through the real potential barrier. This comparison highlights features that are specific to the optical model such as transparency, shape resonances, and peripheral absorption. It also draws attention to the issue of whether simple barrier transmission coefficients are more appropriate for use in the statistical evaporation model.

The characteristics of multistep compound nuclear reactions with the giant resonances as doorway states are discussed in this Brief Report. A cross-section formula describing the above nuclear reactions is derived from the Feshbach-Kerman-Koonin theory with a proper modification of its basic assumptions. Parametrization of this formula leads to an extension of the conventional exciton model. As an application, the derived formula is used to calculate the cross sections of the photonuclear reactions exciting the giant dipole resonances in different nuclei, and the results are in good agreement with experimental data.

A simple Monte Carlo cascade model giving the exclusive description of the heavy ion collisions is described. Comparison with the data on O+Au collisions at 60 and 200 GeV suggests that in this energy region all secondary particles are produced basically by the multiple cascade collisions of the projectile and target nucleons, while the cascading of the produced particles is rather negligible.

The asymmetry parameter for the ground state, mirror decay of polarized ${}_{}{}^{29}{}_{}{}^{}\mathrm{P}$ has been measured. The ${}_{}{}^{29}{}_{}{}^{}\mathrm{P}$ were produced with the ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$(d→,p) reaction, and the sample polarization was determined from a simultaneous measurement of the asymmetry for the pure Gamow-Teller transition to the first excited state in ${}_{}{}^{29}{}_{}{}^{}\mathrm{Si}$ at 1.27 MeV. The result, ${\mathit{A}}_{\mathrm{g}.\mathrm{s}.\mathrm{}}$=0.681±0.086, is in good agreement with the V-A theory of nuclear β decay.

The 2νββ decay matrix element of ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$ has been studied in a large basis shell-model space. The theoretical and experimental ${\mathrm{\beta }}^{\mathrm{-}}$ and ${\mathrm{\beta }}^{+}$ spectra and their relation to 2νββ are discussed. A new empirical effective interaction is found to give the best agreement to ${\mathrm{\beta }}^{\mathrm{-}}$ and ${\mathrm{\beta }}^{+}$ spectra with the effective Gamow-Teller operator σ̃t=0.77σt. The predicted ${\mathit{T}}_{1/2}$=1.9×${10}^{19}$ yr differs by a factor of 2 from the present experimental limit of ${\mathit{T}}_{1/2}$>3.6×${10}^{19}$ yr. We also compare the matrix elements obtained at various levels of the truncation in the shell-model space.

Excited states in the neutron-rich nucleus ${}_{}{}^{142}{}_{}{}^{}\mathrm{Xe}$ have been determined by observing prompt γ rays in fragments from ${}_{}{}^{248}{}_{}{}^{}\mathrm{Cm}$ spontaneous fission. Estimates of the lowest excited-state energies in ${}_{}{}^{142}{}_{}{}^{}\mathrm{Xe}$ based on normal systematics differ considerably from those derived from the ${\mathit{N}}_{\mathit{p}}$${\mathit{N}}_{\mathit{n}}$ scheme. Experimental values are in good agreement with the ${\mathit{N}}_{\mathit{p}}$${\mathit{N}}_{\mathit{n}}$ scheme and illustrate its predictive power in this mass region.

With the use of an on-line isotope separator, the α activity of ${}_{}{}^{186}{}_{}{}^{}\mathrm{Au}$ was identified for the first time. Only one α group (${\mathit{E}}_{\mathrm{\alpha }}$=4653±15 keV) was observed. This transition was found not to be in coincidence with γ rays so that it probably proceeds either to the ${}_{}{}^{182}{}_{}{}^{}\mathrm{Ir}$ ground state or to a low-lying level whose deexciting γ rays could not be detected. The α-decay branching was determined to be (8±2)×${10}^{\mathrm{-}4}$% from which a hindrance factor of 1.9±0.9 was deduced. The 4653-keV α transition must therefore connect the $3^{\mathrm{-}}$ ${}_{}{}^{186}{}_{}{}^{}\mathrm{Au}$ ground state with a ${}_{}{}^{182}{}_{}{}^{}\mathrm{Ir}$ level with the same spin and configuration.

We propose to study inside the nuclei the leptonic decay (${\mathit{e}}^{+}$${\mathit{e}}^{\mathrm{-}}$) of light meson vector ρ, to detect the effect of coupling of nuclear field with a qq¯. If the effect exists we must observe a downward shift (≃120 MeV) in the invariant mass spectrum of the lepton pair. We give a prediction of the distribution expected in future experiments.

Analyzing powers have been measured for elastic and inelastic scattering of 500-MeV protons from ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$. These data for the first $0^{+}$, $2^{+}$, and $4^{+}$ states and the corresponding cross-section data have been analyzed with both Schrödinger and Dirac equation phenomenological coupled-channels methods. Good, qualitatively similar, results are achieved with the two methods.

We show how the incorporation of the canonicity condition, which relates the generator of coordinate and momentum, gives the correct Lagrange multiplier needed to complete the proof that the solution of the adiabatic time-dependent Hartree-Fock theory with the consistency condition fulfills the constrained variation principle designating the valley and thus the canonicity condition is, in principle, a normalization requirement rather than a restriction on the adiabatic time-dependent Hartree-Fock path.