The angular distribution for the breakup of ${}^8\mathrm{B}{\to }^7\mathrm{Be}+p$ on a ${}^{58}\mathrm{Ni}$ target has been measured at an incident energy of 25.75 MeV. The data are inconsistent with first-order theories but are remarkably well described by calculations including higher-order effects. The comparison with theory illustrates the importance of the inclusion of the exotic proton halo structure of ${}^8\mathrm{B}$ in accounting for the data.

The relevance of the partial dynamical symmetry concept for an interacting fermion system is demonstrated. Hamiltonians with partial SU(3) symmetry are presented in the framework of the symplectic shell model of nuclei and shown to be closely related to the quadrupole-quadrupole interaction. Implications are discussed for the deformed light nucleus ${}^{20}\mathrm{Ne}$.

The ratio of the proton's elastic electromagnetic form factors, $G_{E_p}{/G}_{M_p}$, was obtained by measuring $P_t$ and $P_{\ell }$, the transverse and the longitudinal recoil proton polarization, respectively. For elastic $\overrightarrow{e}p\to e\overrightarrow{p}$, $G_{E_p}{/G}_{M_p}$ is proportional to $P_t{/P}_{\ell }$. Simultaneous measurement of $P_t$ and $P_{\ell }$ in a polarimeter provides good control of the systematic uncertainty. The results for the ratio $G_{E_p}{/G}_{M_p}$ show a systematic decrease as $Q^2$ increases from 0.5 to $3.5{\mathrm{GeV}}^2$, indicating for the first time a definite difference in the spatial distribution of charge and magnetization currents in the proton.

We calculate the charge form factor and the longitudinal structure function for ${}^{16}\mathrm{O}$ and compare with the available experimental data, up to a momentum transfer of $4{\mathrm{fm}}^{-1\mathrm{}}$. The ground-state correlations are generated using the coupled-cluster [ $\exp \left(\mathbf{S}\right)$] method, together with the realistic $v18\mathrm{}$ $\mathrm{NN}$ interaction and the Urbana IX three-nucleon interaction. Center-of-mass corrections are dealt with by adding a center-of-mass Hamiltonian to the usual internal Hamiltonian, and by means of a many-body expansion for the computation of the observables measured in the center-of-mass system.

A Comment on the Letter by B. Harss et al., Phys. Rev. Lett. 82, 3964 (1999).

In an experiment at the SISSI/LISE3 facility of GANIL, we used the projectile fragmentation of a primary ${}^{58}{\mathrm{Ni}}^{26+}$ beam at 74.5 MeV/nucleon with an average current of $3\mu \mathrm{A}$ on a natural nickel target to produce very neutron-deficient isotopes. In a 10-day experiment, 287 ${}^{42}\mathrm{Cr}$ isotopes, 53 ${}^{45}\mathrm{Fe}$ isotopes, 106 ${}^{49}\mathrm{Ni}$ isotopes, and 4 ${}^{48}\mathrm{Ni}$ isotopes were unambiguously identified. The doubly magic nucleus ${}^{48}\mathrm{Ni}$, observed for the first time, is the most proton-rich isotope ever identified with an isospin projection $T_z=-4\mathrm{}$. It is probably the last doubly magic nucleus with “classical” shell closures accessible for present-day facilities. Its observation allows us to deduce a lower limit for the half-life of ${}^{48}\mathrm{Ni}$ of $0.5\mu \mathrm{s}$.

Four different combinations of ${}_{44}^{96}\mathrm{Ru}$ and ${}_{40}^{96}\mathrm{Zr}$ nuclei, both as projectile and target, were investigated at the same bombarding energy of $400A\mathrm{MeV}$ using a $4\pi$ detector. The degree of isospin mixing between projectile and target nucleons is mapped across a large portion of the phase space using two different isospin-tracer observables, the number of measured protons and the tritium to ${}^3\mathrm{He}$ yield ratio. The experimental results show that the global equilibrium is not reached even in the most central collisions. Quantitative measures of stopping and mixing are extracted from the data. They are found to exhibit a quite strong sensitivity to the in-medium ( $n,n$) cross section used in microscopic transport calculations.

A Comment on the Letter by W. D. M. Rae, A. C. Merchant, and B. Buck, Phys. Rev. Lett. 69, 3709 (1992). A Comment on the Letter by W. D. M. Rae and A. C. Merchant, Phys. Rev. Lett. 74, 4145 (1995).

The hyperfine structure (hfs) of electron levels of ${}_{92}{}^{238}{}_{}{}^{}U$ ions with the nucleus excited in the low-lying rotational $2^{+}$ state with an energy $E_{2^{+}}=44.91\mathrm{}$ keV is investigated. In hydrogenlike uranium, the hfs splitting for the ${1s}_{1/2}$ ground state of the electron constitutes $1.8$ eV. The hyperfine-quenched (hfq) lifetime of the $1s2p$ ${}^3{P}_0$ state has been calculated for heliumlike ${}_{92}{}^{238}{}_{}{}^{}U$ and was found to be 2 orders of magnitude smaller than for the ion with the nucleus in the ground state. The possibility of a precise determination of the nuclear $g_r$ factor for the rotational $2^{+}$ state by measurements of the hfq lifetime is discussed.

We study the neutron-proton pairing in nuclear matter as a function of isospin asymmetry at finite temperatures and the empirical saturation density using realistic nuclear forces and Brueckner-renormalized single particle spectra. Our computation of the thermodynamic quantities shows that, while the difference of the entropies of the superconducting and normal phases anomalously changes its sign as a function of temperature for arbitrary asymmetry, the grand canonical potential does not; the superconducting state is found to be stable in the whole temperature-asymmetry plane. The pairing gap completely disappears for density asymmetries exceeding ${\alpha }_c=({\rho }_n-{\rho }_p)/\rho \simeq 0.11$.

New vector analyzing-power data on $\overrightarrow{p}+d$ elastic scattering at $E_p=150\mathrm{}$ and $190\mathrm{MeV}$ have been measured. These are presented together with existing data and with recent $\overrightarrow{d}+p$ vector and tensor analyzing power data at $E_d=270\mathrm{}\mathrm{MeV}$. The strong negative extremum of both vector analyzing powers $A_y^p$ and $A_y^d$ at ${\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}\simeq 80°–120°$ is underestimated by Faddeev calculations using modern $\mathrm{NN}$ forces. Inclusion of the Tucson-Melbourne $3N$ force shifts the minima upwards, but with conflicting results for $A_y^p$, and leading to a good description for $A_y^d$. An $A_y^p$ puzzle, previously thought to exist at energies $E_N\le 30\mathrm{MeV}$ only, appears to exist also at intermediate energies.

The positioning of a bubble inside a many fermion system does not affect the volume, surface, or curvature terms in the liquid drop expansion of the total energy. Besides possible Coulomb effects, the only other contribution to the ground state energy of such a system arises from shell effects. We show that the potential energy surface is a rather shallow function of the displacement of the bubble from the center and in most cases the preferential position of a bubble is off-center. Systems with bubbles are expected to have bands of extremely low lying collective states, corresponding to various bubble displacements.

Measurements of magnetic moments and lifetimes of $2_1^{+}$ and $4_1^{+}$ states of ${}^{46,48}\mathrm{Ti}$ and ${}^{50,52}\mathrm{Cr}$ were performed with high accuracy via projectile Coulomb excitation and the technique of transient magnetic fields. The high quality of the data allows for the first time to establish stringent constraints on large scale shell model calculations. Whereas the global behavior of the data is well explained by full $\mathrm{fp}$ shell model calculations, distinct deviations in the $g$ factors and $B\left(E2\mathrm{}\right)$ values of ${}^{46,48}\mathrm{Ti}$ from theoretical predictions can be attributed to excitations of the ${}^{40}\mathrm{Ca}$ core. This suggestion is supported by recent Monte Carlo calculations which provide evidence that ${}^{48}\mathrm{Ca}$ is a better inert core.

The anharmonic vibrator and rotor regions in nuclei are investigated in the framework of the interacting boson model using an ensemble of random one- and two-body interactions. We find a predominance of $L^P{=0\mathrm{}}^{+}$ ground states, as well as strong evidence for the occurrence of both vibrational and rotational band structures. This remarkable result suggests that such band structures represent a far more general (robust) property of the collective model space than is generally thought.

We argue that spontaneous microchannel $S$-matrix correlations and slow spin decoherence result in a sensitivity of the cross sections for strongly dissipative heavy-ion collisions to an arbitrarily small perturbation. Such a sensitivity implies that atomic electrons should influence energetic $\left(\simeq 100\mathrm{MeV}\right)$ heavy-ion reactions. The atomic-electron effects are predicted to be $\simeq 100\%$ of the magnitude of the non-self-averaged oscillating component of the nucleus-nucleus cross sections.

The structure of the halo nucleus ${}^{11}\mathrm{Be}$ has been studied using the reaction ${}^9\mathrm{Be}{(}^{11}\mathrm{Be}{,}^{10}\mathrm{Be}+\gamma )X$ at 60 MeV/nucleon. The ground state structure of ${}^{11}\mathrm{Be}$ is determined by comparing the experimental cross sections to a calculation combining spectroscopic factors from the shell model with $l$-dependent single-particle cross sections obtained in an eikonal model. This experiment shows the dominant $1s$ single-particle character of the ${}^{11}\mathrm{Be}$ ground state and indicates a small contribution of $0d$ admixture in the wave function. After correction for the approximately $22\%$ intensity to excited levels, a clean and precise distribution of parallel momentum for knockout from the $1s$ halo wave function is obtained for the first time.

In deep-inelastic collisions of 8 MeV/nucleon ${}^{70}\mathrm{Zn}$ projectiles with ${}^{198}\mathrm{Pt}$, we have found an $8^{+}$ isomer with $T_{1/2}=23\mathrm{}\left(1\right)\mathrm{ns}$ at 4208 keV in ${}^{68}\mathrm{Ni}$; the $\nu g_{9/2}$ $E2\mathrm{}$ effective charge was determined to be $1.5\left(1\right)e$. In ${}^{69}\mathrm{Cu}$, a $19/2^{-}$ isomer with $T_{1/2}=22\mathrm{}\left(1\right)\mathrm{ns}$ at 3691 keV was identified and its decay data were calculated quite accurately by a parameter-free shell model calculation using empirical input parameters. Proton $2p$- $1h$ excitation, fed by another $T_{1/2}=39\mathrm{}\left(6\right)\mathrm{ns}$ isomer at 3827 keV, induces large collectivity in ${}^{69}\mathrm{Cu}$.

For central collisions of $\left(17–115\right)A\mathrm{MeV}$ ${}^{40}\mathrm{Ar}+\mathrm{Cu}$, Ag, Au, an overall balance is determined for the average mass, energy, and longitudinal momentum. Light charged particles and fragments are separated into forward-focused and isotropic components in the frame of the heaviest fragment. Energy removal by the isotropic component reaches 1–2 GeV. For such high deposition energies, statistical multifragmentation models predict much more extensive nuclear disassembly than is observed.

Light nuclei can be produced in the central reaction zone via coalescence in relativistic heavy-ion collisions. Experiment 864 at BNL has measured the production of ten light nuclei with nuclear number $A=1\mathrm{}$ to $A=7\mathrm{}$ at rapidity $y\simeq 1.9$ and $p_T/A\le 300\mathrm{MeV}/c$. Data were taken with a Au beam of momentum of $11.5A\mathrm{GeV}/c$ on a Pb or Pt target with different experimental settings. The invariant yields show a striking exponential dependence on nuclear number with a penalty factor of about 50 per additional nucleon. Detailed analysis reveals that the production may depend on the spin factor of the nucleus and the nuclear binding energy as well.