Production cross sections of $K^{+}$ and $K^{-}$ mesons have been measured in $\mathrm{C}+\mathrm{C}$ collisions at beam energies per nucleon below and near the nucleon-nucleon threshold. At a given beam energy, the spectral slopes of the $K^{-}$ mesons are significantly steeper than the ones of the $K^{+}$ mesons. The excitation functions for $K^{+}$ and $K^{-}$ mesons nearly coincide when correcting for the threshold energy. In contrast, the $K^{+}$ yield exceeds the $K^{-}$ yield by a factor of about 100 in proton-proton collisions at beam energies near the respective nucleon-nucleon thresholds.

The axial charge of the weak nucleon axial vector current extracted from the anisotropic β-ray angular distributions of spin aligned ${}^{12}\mathrm{B}$ and ${}^{12}\mathrm{N}$ was accounted for mainly in terms of the impulse value $y_{\mathrm{IA}}$ and the soft pion exchange effect term $y_{\mathrm{exch}}$. The experimental value, $y=4.66\mathrm{}\pm 0.06\left(\mathrm{stat}\right)\pm 0.13\left(\mathrm{syst}\right)$, was enhanced by 63% from the impulse value $y_{\mathrm{IA}}=2.85\mathrm{}$ which includes the core polarization effect. The experimental excess of 0.54 over the theoretical value $y_{\mathrm{IA}}{+y}_{\mathrm{exch}}=4.12\mathrm{}$ is accounted for by the in-medium mass reduction from the free nucleon value, if there is such an effect, of about $(12\pm 4)\%$ for the nucleons decaying in the $A=12\mathrm{}$ triad.

The deuteron elastic structure function $A\left(Q^2\right)$ has been extracted in the range $0.7\le Q^2\le 6.0(\mathrm{GeV}/c{)}^2$ from cross section measurements of elastic electron-deuteron scattering in coincidence using the Hall A Facility of Jefferson Laboratory. The data are compared to theoretical models, based on the impulse approximation with the inclusion of meson-exchange currents, and to predictions of quark dimensional scaling and perturbative quantum chromodynamics.

The $A\left(Q^2\right)$ structure function in elastic electron-deuteron scattering was measured at six momentum transfers $Q^2$ between 0.66 and $1.80(\mathrm{GeV}/c{)}^2$ in Hall C at Jefferson Laboratory. The scattered electrons and recoil deuterons were detected in coincidence, at a fixed deuteron angle of 60.5°. These new precise measurements resolve discrepancies between older sets of data. They put significant constraints on existing models of the deuteron electromagnetic structure, and on the strength of isoscalar meson exchange currents.

The breakup of ${}^{12}\mathrm{Be}$ into ${}^6\mathrm{He}{+}^6\mathrm{He}$ and ${}^4\mathrm{He}{+}^8\mathrm{He}$ has been studied using a 378 MeV ${}^{12}\mathrm{Be}$ beam inelastically excited by ${}^{12}\mathrm{C}$ and $({\mathrm{CH}}_2{)}_n$ targets. The measurements indicate that breakup occurs from rotational states in the 10 to 25 MeV excitation energy interval, with spins in the range of $4ħ$ to $8ħ$. The inferred moment of inertia is consistent with the cluster decay of an exotic molecular structure in ${}^{12}\mathrm{Be}$, which may be associated with an $\alpha -4n-\alpha$ cluster configuration.

The effect of dipole Coulomb coupling to breakup states in the elastic scattering of ${}^{11}\mathrm{Li}$ on ${}^{208}\mathrm{Pb}$ at 24 MeV is evaluated. Recently measured ${}^{11}\mathrm{Li}$ $B\left(E1\mathrm{}\right)$ distributions are used to obtain the dynamic polarization potential that describes the effect of this coupling. Sizable deviations from the Rutherford cross sections are obtained, which constitute a signature of dipole polarizability. The contribution of quadrupole Coulomb excitation is found to be negligible.

The use of chemically selective laser ionization combined with $\beta$-delayed neutron counting at CERN/ISOLDE has permitted identification and half-life measurements for 623-ms ${}^{61}\mathrm{Mn}$ up through 14-ms ${}^{69}\mathrm{Mn}$. The measured half-lives are found to be significantly longer near $N=40\mathrm{}$ than the values calculated with a quasiparticle random-phase-approximation shell model. Gamma-ray singles and coincidence spectroscopy has been performed for ${}^{64,66}\mathrm{Mn}$ decays to levels of ${}^{64,66}\mathrm{Fe}$, revealing a significant drop in the energy of the first $2^{+}$ state in these nuclides that suggests an unanticipated increase in collectivity near $N=40\mathrm{}$.

Complete fusion excitation functions for ${}^9\mathrm{Be}{+}^{208}\mathrm{Pb}$ have been measured to high precision at near barrier energies. The experimental fusion barrier distribution extracted from these data allows reliable prediction of the expected complete fusion cross sections. However, the measured cross sections are only 68% of those predicted. The large cross sections observed for incomplete fusion products support the interpretation that this suppression of fusion is caused by ${}^9\mathrm{Be}$ breaking up into charged fragments before reaching the fusion barrier. Implications for the fusion of radioactive nuclei are discussed.

We present measurements of the multiplicity of charged particles ( $N_c$) and intermediate mass fragments (IMFs) for ${}^{58}\mathrm{Fe}{+}^{58}\mathrm{Fe}$ and ${}^{58}\mathrm{Ni}{+}^{58}\mathrm{Ni}$ at incident energies of 45 to 105 MeV/nucleon. We find that the neutron-rich system emits more IMFs as a function of $N_c$ at low incident energies while at the highest energy we observe a much smaller difference between the two systems. Expanding emitting source and statistical multifragmentation simulations reproduce the difference between the two systems at low energies while a charge percolation simulation describes the results at the highest energy.

The liquid-gas phase transition in finite systems is studied within a lattice gas model in the canonical ensemble. In the coexistence region, the existence of conservation laws is shown to result in anomalies in the associated equation of state leading, for example, to negative compressibility due to surface effects. The associated partitions exhibit scaling behavior inside the coexistence zone. When the thermodynamical limit is taken this scaling disappears while the anomaly of the equation of state becomes the usual nonanalytical behavior. Therefore, in the fragmentation of small systems such as nuclei the experimentally observed critical behavior is demonstrated to be compatible with a first order phase transition because of finite size effects.

The effects of isospin mixing on the observables for parity-violating electron scattering are investigated within the framework of the nuclear shell model for ${}^{12}\mathrm{C}$, ${}^{16}\mathrm{O}$, and ${}^{28}\mathrm{Si}$. Contributions due to mixing with low-lying states as well as admixtures of $1p-1h$ configurations are accounted for. The consequences regarding precision tests of the standard model are addressed.

The nuclei ${}^{48}\mathrm{Ca}$ and ${}^{90}\mathrm{Zr}$ were investigated in $180°$ high-resolution inelastic electron scattering for momentum transfers $q\simeq 0.35–0.8$ ${\mathrm{fm}}^{-1\mathrm{}}$. The complete $M2\mathrm{}$ strength could be extracted in both nuclei up to excitation energies of about 15 MeV. Second-random-phase approximation calculations successfully describe the strong fragmentation of the experimental strength distributions. Contrary to previous experimental findings, suggesting a severe reduction, the deduced quenching of $M2\mathrm{}$ spin matrix elements is comparable to the $M1\mathrm{}$ case. A quantitative reproduction of the data requires the presence of appreciable orbital strength which can be interpreted as a torsional elastic vibration (“twist mode”).

The spontaneous ultraviolet luminescence reported [G. M. Irwin and K. H. Kim, Phys. Rev. Lett. 79, 990 (1997); D. S. Richardson et al., ibid. 80, 3206 (1998)] from ${}^{233}\mathrm{uranium}$ compounds and ascribed to an ultraviolet gamma-ray emission from the metastable ${}^{229}\mathrm{thorium}$ daughter is actually ${\mathrm{N}}_2$ discharge emission induced in the air surrounding the sample by the sample radioactivity. The UV spectrum from high elemental and isotopic purity ${}^{233}{\mathrm{UO}}_3$ reported here also exhibits a line at 391.3 nm that does not appear to be due to electric discharge ${\mathrm{N}}_2$ emission.

A microscopic approach to fragment momentum distributions in diffractive breakup of Borromean two-neutron halo nuclei is developed, taking into account the correlated structure of the halo continuum. The crucial role of the low-lying three-body resonances and soft modes in determining distribution characteristics is demonstrated.

We report on a first measurement of tensor analyzing powers in quasielastic electron-deuteron scattering at an average three-momentum transfer of $1.7{\mathrm{fm}}^{-1\mathrm{}}$. Data sensitive to the spin-dependent nucleon density in the deuteron were obtained for missing momenta up to $150\mathrm{MeV}/c$ with a tensor polarized ${}^2\mathrm{H}$ target internal to an electron storage ring. The data are well described by a calculation that includes the effects of final-state interaction, meson-exchange and isobar currents, and leading-order relativistic contributions.

$E0\mathrm{}$ strength distributions in ${}^{90}\mathrm{Zr}$, ${}^{116}\mathrm{Sn}$, ${}^{144}\mathrm{Sm}$, and ${}^{208}\mathrm{Pb}$ have been measured with inelastic scattering of 240-MeV $\alpha$ particles between $0°\le {\theta }_{\mathrm{lab}}\le 6°$ to greater precision than previously available. In Sn, Sm, and Pb, $E0\mathrm{}$ strength was concentrated in approximately symmetric peaks, whereas in ${}^{90}\mathrm{Zr}$ it had a significant high energy tail. Comparing with microscopic calculations using the Gogny interaction, these and our previously reported results for ${}^{40}\mathrm{Ca}$ are consistent with a nuclear matter incompressibility of $231\pm 5\mathrm{MeV}$. Previous data gave an average of 215 MeV and the value for different nuclei disagreed by up to 40 MeV.

A sample of $6.3\times {10}^{14}$ nuclei of the 4-quasiparticle isomer of ${}^{178}\mathrm{Hf}$ having a half-life of 31 yr and excitation energy of 2.446 MeV was irradiated with x-ray pulses from a device typically used in dental medicine. It was operated at 15 mA to produce bremsstrahlung radiation with an end point energy set to be 70 or 90 keV. Spectra of the isomeric target were taken with a high purity Ge detector. Intensities of selected transitions in the normal decay cascade of the ${}^{178}\mathrm{Hf}$ isomer were found to increase by about $4\%$. Such an accelerated decay is consistent with an integrated cross section of $1\times {10}^{-21\mathrm{}}\mathrm{cm}{}^2\mathrm{keV}$ for the resonant absorption of x rays to induce gamma decay.

The fission fragment anisotropies for ${}^{12}\mathrm{C}{+}^{198}\mathrm{Pt}$ populating ${}^{210}\mathrm{Po}$ are found to be systematically higher than that for ${}^{12}\mathrm{C}{+}^{194}\mathrm{Pt}$, the difference decreasing over the energy range $1.0\le E/V_B\le 1.4$. The parameters required for a statistical model analysis of the data were constrained by fission cross section data and by measuring evaporation residue cross sections. While the measured anisotropies for ${}^{12}\mathrm{C}{+}^{194}\mathrm{Pt}$ are in agreement with the saddle point model calculations, those for ${}^{12}\mathrm{C}{+}^{198}\mathrm{Pt}$ are considerably larger. The data are suggestive of a significant shell effect in the anisotropies of fission fragments emitted from ${}^{210}\mathrm{Po}$ with neutron magic number, $N=126\mathrm{}$.

The ${}^{18}\mathrm{N}$ ground state magnetic moment $|\mu |=0.135\mathrm{}\left(15\right){\mu }_N$ has been measured using a modified $\beta$ nuclear magnetic resonance technique. The value is compared to shell-model calculations. Spin-aligned ${}^{18}\mathrm{N}$ projectile fragments were produced in the fragmentation of ${}^{22}\mathrm{Ne}$ at 60.3 MeV/nucleon. Polarization of the nuclear spins was resonantly induced by a combined magnetic dipole, electric quadrupole, and radio frequency interaction. This is the first application of a new method that allows production of polarized nuclei from spin-aligned projectile fragments, allowing one to measure $\beta$ asymmetries. The method opens a new range of applications to study static dipole and quadrupole moments of exotic nuclei near the drip lines.

The properties of the lowest two-phonon states in ${}^{208}\mathrm{Pb}$ built on the collective octupole vibration are studied within the quasiparticle phonon model. Calculations including up to three-phonon coupling yield a strong fragmentation of the $6^{+}$ member of the multiplet, explaining the failure of recent heavy ion Coulomb excitation experiments used to observe this state. Some splitting of the $2^{+}$ strength is predicted while the $0^{+}$ and $4^{+}$ members remain relatively pure. The present results also question the proposed signature for the two-octupole states of enhanced $E1\mathrm{}$ decays to one-phonon states.