A Hartree-Fock oriented study of the effective interactions in the mass region $A=16-80\mathrm{}$ reveals that, quite contrary to the widely held belief, their like-particle parts have almost the same deformation-producing character as their neutron-proton parts. The result is consistent with the relatively recent observations concerning the dramatic onset of large deformations in the highly neutron-rich Zr isotopes.

NUCLEAR STRUCTURE Study of the deformation-producing tendency of the like-particle interactions; Hartree-Fock framework; absence of rotational features in neutron-excess nuclei in the $2s-1d$ and $2p-1f$ shells; role of single-particle energies; onset of large deformations in highly neutron-rich zirconium isotopes; cranked Hartree-Fock calculations in the nuclei ${}_{}{}^{100,102}{}_{}{}^{}\mathrm{Zr}$.

The giant resonance region of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ has been investigated by small angle scattering of 104 MeV $\alpha$ particles. No evidence was found for concentrated monopole strength. Monopole strength around $E_x=9.15\mathrm{}$ MeV ($\Gamma =1.8\mathrm{}$ MeV, 2.1% energy-weighted sum rule) recently observed in a ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ scattering experiment could not be confirmed.

NUCLEAR REACTIONS ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$($\alpha$,${\alpha }^{\prime }$); $E_{\alpha }=104\mathrm{}$ MeV. Measured $E_x$,$\sigma \left(\theta \right)$ for giant resonance region.

States in ${}_{}{}^{243}{}_{}{}^{}\mathrm{Am}$ have been investigated via Coulomb excitation by observing elastically and inelastically scattered 17-MeV ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ ions. Only the excitation of members of the ${\frac{5}{2}}^{-}\left[523\mathrm{}\downarrow \right]$ ground-state rotational band could be detected; these include the previously unknown ${\frac{11}{2}}^{-}$ and ${\frac{13}{2}}^{-}$ rotational states. With an intrinsic quadrupole moment, $Q_{20}$, of 12.02±0.09 eb, an adequate description of the excitation probabilities for all observed members of the ground-state rotational band was obtained. The deduced ground-state spectroscopic quadrupole moment is 4.29±0.03 eb.

NUCLEAR REACTIONS ${}_{}{}^{243}{}_{}{}^{}\mathrm{Am}$($\alpha$,${\alpha }^{\prime }$), $E=17\mathrm{}$ MeV; measured $\sigma (E_{{\alpha }^{\prime }};\theta =150\mathrm{}°)$; ${}_{}{}^{243}{}_{}{}^{}\mathrm{Am}$ levels; deduced $B\left(E2\right)$, $B\left(E4\right)$, $q$. Enriched target.

We have measured the cross sections for production of the astrophysically prominent 6.13-MeV gamma ray from the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$($p$,$p^{\prime }\gamma$)${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ reaction at $E_{\mathrm{lab}}^p=23.7\mathrm{} \mathrm{and} 44.6$ MeV to be 58.9 and 40.4 mb, respectively. Our results are compared to earlier measurements.

NUCLEAR REACTIONS ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$($p$,$p^{\prime }\gamma$)${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$. $E=23.7\mathrm{} \mathrm{and} 44.6$ MeV. Measured gamma-ray angular distributions and production cross sections. Implications for gamma-ray astronomy.

We have measured the deep inelastic scattering of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ + ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ at $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}=32.1\mathrm{}$ MeV and ${\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}=60-110\mathrm{}°$ using the kinematical coincidence technique with a large-angle detection system. We found no evidence for the existence of a low-$l$ window leading to deep inelastic scattering as predicted by time-dependent Hartree-Fock calculations.

NUCLEAR REACTIONS ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$(${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$*) ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$* deep inelastic scattering, $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}=32.1\mathrm{}$ MeV; coincidence measurement of both ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ fragments; measured $\sigma (Q,\theta )$.

The charge form factor of ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$ is calculated with a semimicroscopic method in which the Pauli principle is taken fully into account but the intercluster relative motion is parametrized in a way guided by cluster-model considerations. The results show that there is a large degree of $t+\alpha$ clustering in the ground state of ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$ and that specific distortion effects are fairly important in this system.

NUCLEAR STRUCTURE ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$; charge form factor with semimicroscopic approach.

Both coherent and incoherent final state rescatterings are needed to account for the observed ($p$,$2p$) angular distributions and the hitherto unexplained analyzing powers observed for high energy backwardly produced protons (the "cumulative" region).

NUCLEAR REACTIONS High momentum components; analyzing power; $p$,$2p$ reactions.

The solution of the Baer-Kouri-Levin-Tobocman many-body scattering equations by means of a finite basis expansion method has been carried out for a simple three-body system. Various versions of the Baer-Kouri-Levin-Tobocman formalism and approximations to it were compared. The distorted wave Baer-Kouri equations was the version that worked best. The finite basis method was found to yield accurate values for binding energies and transition amplitudes only when continuum intermediate state contributions were small.

NUCLEAR REACTIONS Test of the finite basis expansion method for the BKLT equations.

Exact quantum-mechanical coupled-channels and classical-limit calculations are compared for the case of a very-heavy-ion reaction exciting strongly collective states via Coulomb and complex nuclear potentials. The calculations are in excellent agreement for transitions which are likely to be experimentally important and provide further support for the classical localization picture in very-heavy-ion collisions.

NUCLEAR REACTIONS HI coupled-channels inelastic scattering. Comparison of quantal and classical-limit theories.

A kinematically complete experiment has been performed to study $\alpha$-induced deuteron breakup under the same experimental conditions as in a previous experiment. With respect to the results of the latter experiment, our correlation cross sections are about one order of magnitude larger, while they are of the same order as those at higher energies. Our analysis indicates that the experimental spectra are rather well reproduced with models involving only two-body interactions. The hypothesis of three-body forces is, therefore, not required to interpret the data.

NUCLEAR REACTIONS ${}_{}{}^2{}_{}{}^{}\mathrm{H}(\alpha ,p\alpha )n$, $E=10.27, 11.3, \mathrm{and} 13$ MeV; measured $\sigma (E_p,{\theta }_p,{\theta }_{\alpha })$; solid target.

The simple treatment of Coulomb distortion in intermediate energy hadron-nucleus scattering developed in the analytic approximation of Amado, Dedonder, and Lenz is implemented. In three examples we compare the impact of the Coulomb distortion calculated with their analytic formula with that calculated by the standard numerical method. These calculations are compared with the data for 800 MeV $p$-${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ and 291 MeV ${\pi }^{\pm }$-${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ elastic scattering. We find that the analytic approximation accurately reproduces the effect of the Coulomb distortion as calculated numerically while illuminating the essentially simple physics involved.

NUCLEAR REACTIONS Analytic approximation for Coulomb distortion in intermediate energy hadron-nucleus scattering. Example calculations for 800 MeV $p$-${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ and 291 MeV ${\pi }^{\pm }$-${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ elastic scattering.

Leeman et al. measured ${}_{}{}^2{}_{}{}^{}\mathrm{H}\mathrm{}(d,pp)\mathrm{nn}$ cross sections at 80 MeV. They interpreted their results in terms of double spectator processes and had limited success in fitting their spectra. We obtain good fits to all their reported data by assuming final-state interactions between both final $n-p$ pairs and ignoring the double spectator process.

NUCLEAR REACTIONS ${}_{}{}^2{}_{}{}^{}\mathrm{H}\mathrm{}(d,pp)\mathrm{nn}$, $E=80\mathrm{}$ MeV; calculated $\sigma (E_1,E_2,{\theta }_1,{\theta }_2)$ assuming $n-p$ final-state interactions. Improved fits over original interpretation assuming double spectator process.

Angular distributions of photofission of ${}_{}{}^{232}{}_{}{}^{}\mathrm{Th}$ have been measured using bremsstrahlung γ beams in the (5.4-6.4) MeV range. With decreasing energy below 6 MeV the angular anisotropy decreases strongly and, moreover, a shelf appears in the isotropic component of the yield. These effects are interpreted in terms of a competition between prompt and delayed fission. Vibrational resonances in the $1^{-0\mathrm{}}$ and $2^{+0\mathrm{}}$ channels are detected.

NUCLEAR REACTIONS, FISSION Angular distributions and yields of subthreshold photofission of ${}_{}{}^{232}{}_{}{}^{}\mathrm{Th}$ in the (5.4-6.4) MeV range.

The vector and tensor analyzing powers of the continuum energy spectra following ${}_{}{}^3{}_{}{}^{}\mathrm{Nb}$($\overrightarrow{d}$,$d^{\prime }X$) and ${}_{}{}^{93}{}_{}{}^{}\mathrm{Nb}$($\overrightarrow{d}$,$\mathrm{pX}$) reactions were measured for the first time at $E_d=56\mathrm{}$ MeV. The vector analyzing powers obtained are surprisingly large and positive in the backward hemisphere. Nonvanishing tensor analyzing powers were observed up to an excitation energy of about 40 MeV. Simple distorted-wave Born-approximation calculations were made to compare the observed vector and tensor analyzing powers.

NUCLEAR REACTIONS ${}_{}{}^{93}{}_{}{}^{}\mathrm{Nb}$($\overrightarrow{d}$,$d^{\prime }X$) and ${}_{}{}^{93}{}_{}{}^{}\mathrm{Nb}$($\overrightarrow{d}$,$\mathrm{pX}$), $E=56\mathrm{}$ MeV; measured continuum spectra at angles between 20° and 137°; extracted $\frac{d^2\sigma }{d\Omega }\mathrm{dE}$, $A_y$, $A_{\mathrm{xx}}$, and $A_{\mathrm{yy}}$; compared with simple DWBA calculations.

The possibility considered is that a nonstatic ordered phase can be realized as a spin-isospin dependent breathing mode in the ground state of nuclei. A quantitative analysis, carried out within the framework of a macroscopic collective model and valid for light nuclei only, shows that such a mode is favored by the one-pion-exchange potential only if realized as a one-dimensional breathing oscillation and for large deformations and at densities much higher than normal nuclear density. The relevance of this result to precursor phenomena is emphasized.

NUCLEAR STRUCTURE One-pion-exchange contribution zero-point energy spin-isospin breathing mode.

The deuteron magnetic structure function $B\left(q^2\right)$ is calculated in the one-photon exchange approximation using the recently described approach based on the Bethe-Salpeter equation. In this approach contributions to the deuteron electromagnetic form factors when the spectator or the struck nucleon is on-mass-shell appear with equal weight. Results obtained without any free parameters and without including any meson-exchange currents are in good agreement with the available data. Predictions are made for $B\left(q^2\right)$ up to $q^2=8\mathrm{}$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$ and they show a minimum at $q^2\simeq 2 or 2.5$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$ depending on the choice of the $\mathrm{NN}$ interaction. This is in sharp contrast with the exchange-current calculations which do not exhibit a minimum for any $q^2<~8$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$.

NUCLEAR REACTIONS ${}_{}{}^2{}_{}{}^{}\mathrm{H}$($e$,$e$), $q^2<~8$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$, calculated $B\left(q^2\right)$, compared with experimental data.

At energies well above the Coulomb barrier, the slope of the angular distributions of excitation-energy bins extracted from the spectra of most outgoing products observed in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$-induced reactions is found to be a smooth function of the measured $Q$ value. A friction model is proposed which closely reproduces this dependence.

NUCLEAR REACTIONS $X({}_{}{}^{16}{}_{}{}^{}\mathrm{O},Y)$, $X={}_{}{}^{12}{}_{}{}^{}\mathrm{C},{}_{}{}^{27}{}_{}{}^{}\mathrm{Al},{}_{}{}^{60}{}_{}{}^{}\mathrm{Ni},{}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$, $Y=\mathrm{projectilelike}\mathrm{fragments}$ ($Z=3-9\mathrm{}$), $E=100-315\mathrm{}$ MeV. Correlation between slopes of $\sigma (E,Z,\theta )$ and energy-loss found. Friction model proposed. Deduced frictional coefficients, interaction times.

We consider the Schrödinger problem for a Coulomb plus short-range interaction with complex coupling parameter $\lambda$, and we study the poles of the $T$ operator for such a potential as functions of $\lambda$. The trajectories of these poles in the complex plane are to a great extent determined by saddle points. Assuming that the short-range interaction is separable, we derive accurate asymptotic formulas for the infinite number of saddle points and for the associated critical values of $\lambda$. In the particular case of the Coulomb plus Yamaguchi potential we obtain excellent agreement with previously published purely numerical results.

NUCLEAR REACTIONS Scattering theory, Coulomb level shifts, $S$-matrix poles, exotic atoms, coupled charged-particle channels.

Cross-section and analyzing-power data are presented for the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$($\overrightarrow{p}$,$p^{\prime }$)${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ reaction at a bombarding energy of 120 MeV. Calculations are made in the distorted-wave impulse approximation with an antisymmetrized on-shell $t$ matrix obtained from nucleon-nucleon scattering amplitudes at 140 MeV. The results are in much better agreement with the data for the cross sections than for the analyzing powers. Significant discrepancies with the data at large momentum transfers are found. Analysis of the contributions for the observed $2^{-}$ transitions shows strong sensitivity to the underlying configurations and appear to be well described by the shell-model wave functions of Millener and Kurath.

NUCLEAR REACTIONS ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$($\overrightarrow{p}$,$p^{\prime }$)${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, $E=120\mathrm{}$ MeV, measured $\sigma (E,\theta )$, $A_y\left(\theta \right)$; $\theta =6\mathrm{}°-60\mathrm{}°$, $E_x=0-17\mathrm{}$ MeV. DWIA analysis.

A series of distorted-wave impulse-approximation calculations is carried out for the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$($\overrightarrow{p}$,$p^{\prime }$)${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ reaction to the $1^{+}$, $T=1\mathrm{}$ state at 15.11 MeV. Consideration is given to variations in the parameters of the optical potential, the bound-state wave functions, the transition amplitudes, and the effective interaction. Most results are found to be stable against reasonable changes in the parameters and did not resolve the discrepancies between the calculations and the data at large momentum transfer. However, some improvements were found if the lowest partial waves are eliminated.

NUCLEAR REACTIONS ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$($\overrightarrow{p}$,$p^{\prime }$), $E=120\mathrm{}$ MeV, $E_x=15.11\mathrm{}$ MeV; DWIA calculations with parameter variations.