It is demonstrated by the example of the $E_x=16.28\mathrm{}\mathrm{MeV}$, $J^{\pi }{;T=1\mathrm{}}^{-};6\mathrm{}$ state in ${}^{90}\mathrm{Zr}$ that a high-resolution ${}^{90}\mathrm{Zr}({e,e}^{\prime }p{)}^{89}\mathrm{Y}$ experiment can provide a nearly model-independent full characterization of all relevant spectroscopic properties of an isobaric analog state. The proton angular correlation data and branching ratios determine the total and partial widths into radiative and particle decay channels. A phenomenological wave function is deduced from the form factor.

We have made improved measurements of the ${}^{142,144}\mathrm{Nd}(n,\gamma )$ cross sections and investigated the s-process nucleosynthesis in the Ce-Nd-Sm region. Recently discovered anomalies of the Nd isotopes in silicon carbide grains from the Murchison meteorite have been interpreted in terms of pure s-process material from an AGB star. With previous cross section data the s-process origin could not be confirmed, whereas our new data convincingly support the interpretation that these isotopic anomalies were carried into the early solar system inside carbon dust particles that condensed in outflowing winds of presolar AGB stars.

Halo nuclei are studied using a $G$-matrix interaction derived from the Paris and Bonn potentials and employing a two-frequency shell model approach. It is found that the core-polarization effect is dramatically suppressed in such nuclei. Consequently, the effective interaction for halo nucleons is almost entirely given by the bare $G$ matrix alone, which presently can be evaluated with a high degree of accuracy. The experimental pairing energies between the two halo neutrons in ${}^6\mathrm{He}$ and ${}^{11}\mathrm{Li}$ nuclei are satisfactorily reproduced by our calculation. It is suggested that the fundamental nucleon-nucleon interaction can be probed in a clearer and more direct way in halo nuclei than in ordinary nuclei.

We study the energy dependence of collective (hydrodynamic-like) nuclear matter flow in (400–1970)A MeV $\mathrm{Ni}+\mathrm{Au}$ and (1000–1970)A MeV $\mathrm{Ni}+\mathrm{Cu}$ reactions. The flow increases with energy, appears to reach a maximum, and then to decrease at higher energies. A way of comparing the energy dependence of flow values for different projectile-target mass combinations is introduced, which demonstrates a more-or-less common scaling behavior among flow values from different systems.

Elliptical energy flow in noncentral $\mathrm{Au}(11.7A\mathrm{GeV})$ on Au reactions is studied comparing results obtained in two different modes of the relativistic quantum molecular dynamics approach (mean field and cascade). The final azimuthal asymmetries in the central rapidity region are very sensitive to the pressure at maximum compression, because they involve a partial cancellation between early squeeze out and subsequent flow in the reaction plane. Analysis of elliptic flow may lead to much stronger constraints on the magnitude of pressure in ultradense nuclear matter than are available today.

Differential cross sections for p- ${}^6\mathrm{He}$ and p- ${}^8\mathrm{He}$ elastic scattering have been measured in inverse kinematics at small momentum transfers up to $|t|=0.05\mathrm{}(\mathrm{GeV}/c{)}^2$ and projectile energies of about 700 MeV/nucleon. Nuclear matter densities deduced from the data are consistent with the concept that ${}^6\mathrm{He}$ and ${}^8\mathrm{He}$ nuclei have an $\alpha$-like core and a significant neutron skin. The rms radii of the nuclear matter distributions were determined to be $R_m$ ${(}^6\mathrm{He})=2.30\mathrm{}\pm 0.07\mathrm{fm}$ and $R_m$ ${(}^8\mathrm{He})=2.45\mathrm{}\pm 0.07\mathrm{fm}$.

Collisions of ${}^{11}\mathrm{Li}+p$ at $68A\mathrm{MeV}$ have been studied by correlational measurements. An excited state of ${}^{11}\mathrm{Li}$ at $E^{*}\simeq 1.3\mathrm{MeV}$ was observed. The measured angular distributions show the dipole nature of the excitation of the 1.3-MeV peak. The structure of the excited states and the ground state of ${}^{11}\mathrm{Li}$ is discussed.

Yrast superdeformed bands for even-even nuclei of the mass-190 region are described by the projected shell model. Excellent agreement with available data for all isotopes is obtained. Our calculation of electromagnetic properties and pairing correlations provides a microscopic understanding of the observed gradual increase of dynamical moments of inertia with angular momentum in this mass region and suggests that for superdeformation it is not very meaningful to distinguish between Coriolis antipairing and gradual high- $j$ orbital alignment.

Transverse mass spectra of pions, kaons, and protons from the symmetric heavy-ion collisions 200 $A$ GeV $\mathrm{S}+\mathrm{S}$ and 158 $A$ GeV $\mathrm{Pb}+\mathrm{Pb}$, measured in the NA44 focusing spectrometer at CERN, are presented. The mass dependence of the slope parameters provides evidence of collective transverse flow from expansion of the system in heavy-ion induced central collisions.

Systematic experimental evidence is presented for the decay of nuclear matter from toroidal geometries using reactions of ${}^{86}\mathrm{Kr}{+}^{93}\mathrm{Nb}$ at incident energies ranging from 35 to 95 MeV/nucleon. The decay of noncompact geometries is established through two charge-related observables, and the distinction between toroidal and bubblelike geometries is achieved through event shape analysis. Indications of these exotic geometries appear for beam energies between 60 and 75 MeV/nucleon.

Lifetimes of states in four of the $M1\mathrm{}$ bands in ${}^{198,199}\mathrm{Pb}$ have been determined through a Doppler-shift attenuation method measurement performed using the Gammasphere array. The deduced $B\left(M1\mathrm{}\right)$ values, which are a sensitive probe of the underlying mechanism for generating these sequences, show remarkable agreement with tilted axis cranking (TAC) calculations. The results represent clear evidence for a new concept in nuclear excitations: “magnetic rotation.”

We report measurements of $\sigma \left(\theta \right)$, $A\left(\theta \right)$, and polarization transfer for the ${}_{}{}^{28}{}_{}{}^{}S\mathrm{i}(\overrightarrow{p},{\overrightarrow{p}}^{\prime }){}_{}{}^{28}{}_{}{}^{}S\mathrm{i}$ reaction to the $6^{-},T=1\mathrm{}$ state at 14.36 MeV initiated with 198 MeV polarized protons. Normalization of the transition strength in the distorted-wave impulse approximation (DWIA) to inelastic electron scattering overpredicts the spin-longitudinal cross section by more than a factor of 2, while the spin-transverse cross section is nearly correct and the spin-orbit cross section is underpredicted. A reduced in-medium $\rho$-meson mass reproduces some of these features, while strong relativistic mean field or Pauli blocking effects are too small.

The eigenstates of a Woods-Saxon axially deformed potential are calculated by solving the corresponding coupled channel Schrödinger equation with outgoing boundary condition at large distances, thus providing both the bound states and the outgoing resonances. The level energies and conditions for bound states to become narrow resonances, and vice versa, are investigated as a function of the deformation. These studies may be important to interpret future measurements with nuclei close to the nucleon drip line.

The ratio of pre-equilibrium neutrons to protons from collisions of neutron-rich nuclei is studied as a function of their kinetic energies. This ratio is found to be sensitive to the density dependence of the nuclear symmetry energy, but is independent of the compressibility of symmetric nuclear matter and the in-medium nucleon-nucleon cross sections. The experimental measurement of this ratio thus provides a novel means for determining the nuclear equation of state of asymmetric nuclear matter.

The breakup temperatures for central $\mathrm{Au}+\mathrm{Au}$ collisions at $35A\mathrm{MeV}$ have been determined from the relative populations of excited states of ${}^5\mathrm{Li}$, ${}^4\mathrm{He}$, and ${}^{10}\mathrm{B}$ fragments and nine double ratios involving the yields of elements with $1\le Z\le 6$. Unlike results reported at significantly higher energies, all thermometers yield temperatures that are consistent within the experimental uncertainties. Extrapolation of the data to zero impact parameter yields $T_{\mathrm{em}}=4.6\mathrm{}\pm 0.4\mathrm{MeV}$, somewhat lower than the temperature assumed in statistical multifragmentation model calculations which describe most of the other features of this reaction.

Excitation functions of proton-proton elastic scattering cross sections have been measured in narrow steps for projectile momenta $p_p$ (energies $T_p$) from $1100$ to $3300\mathrm{MeV}/c$ (500 to 2500 MeV) in the angular range $35°\le {\Theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}\le 90°$ with a detector providing $\Delta {\Theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}\approx 1.4°$ resolution. Measurements have been performed continuously during projectile acceleration in the cooler synchrotron COSY with an internal ${\mathrm{CH}}_2$ fiber target, taking particular care to monitor luminosity as a function of $T_p$. The advantages of this experimental technique are demonstrated, and the excitation functions obtained are compared to existing cross section data. No evidence for narrow structures was found.

A Comment on the Letter by S. Gardner, C. J. Horowitz, J. Piekarewicz, Phys. Rev. Lett. 75, 2462 (1995). The authors of the Letter offer a Reply.

A Reply to the Comment by Simon Capstick and B. D. Keister.

An exact solution of the time-dependent Dirac equation for ionization and pair production induced by ultrarelativistic heavy ion collisions is presented. Exact transition probabilities, equivalent to those that would be obtained in an untruncated basis coupled channels calculation, are presented. Exact bound-electron positron pair production probabilities are calculated to be mostly smaller than those calculated with the same potential in perturbation theory at impact parameters small enough for differences to occur.

Deuterium molecules were obtained by recombination, on a copper surface, of deuterium atoms prepared in specific hyperfine states. The molecules were stored for about 5 ms in an open-ended cylindrical cell, placed in a 23 mT magnetic field, and their tensor polarization was measured by elastic scattering of 704 MeV electrons. The results of the measurements are consistent with the deuterium molecules retaining the tensor polarization of the initial atoms.