Sum rules for the total- and scissors-mode $M1\mathrm{}$ strength in odd- $A$ nuclei are derived within the single- $j$ interacting boson-fermion model. We discuss the physical content and geometric interpretation of these sum rules and apply them to ${}^{167}\mathrm{Er}$ and ${}^{161}\mathrm{Dy}$. We find consistency with the former measurements but not with the latter.

$4\pi$ studies of multiple charged-particle emission in GeV ${\pi }^{-}$- and proton-induced reactions on a Au target have been performed with the ISiS detector array. Multiplicity, charge, and angular distributions yield nearly identical results for both $p$ and ${\pi }^{-}$ beams, suggesting an independence of hadron type in initiating the fast cascade and subsequent energy deposition in the struck nucleus. The excitation functions show little sensitivity to beam momentum, consistent with a saturation in deposition energy and the concept of limiting fragmentation. However, the intermediate mass fragment multiplicities and fragment charge distributions depend strongly on collision violence.

The reaction $\mathrm{pp}\to p{\pi }^{+}N$ has been studied at three energies ( $T_p=1520\mathrm{}$, 1805, and 2100 MeV) and six angles from 0° up to 17° (laboratory). Several narrow states have been observed in missing mass spectra at 1004, 1044, and 1094 MeV. Their widths are typically 1 order of magnitude smaller than the widths of $N^{*}$ or $\Delta$. Possible biases are discussed. These masses are in good agreement with those calculated within a simple phenomenological mass formula based on color magnetic interaction between two colored quark clusters.

Tilted-axis rotation, arising from Fermi-aligned configurations, has been observed for the first time to cause backbending in an odd-proton nucleus. In ${}^{181}\mathrm{Re}$, two $t$-bands are found to be energetically favored relative to the usual rotation-aligned $s$-bands, presenting an alternative form of cold nuclear rotation. Interactions between the bands are weak, and unambiguous comparisons with tilted-axis-cranking calculations can be made.

The isoscalar giant dipole resonance (ISGDR) in ${}^{208}\mathrm{Pb}$ has been investigated using inelastic scattering of 200 MeV $\alpha$ particles at and near 0° where the angular distribution of the ISGDR can be clearly differentiated from those of other modes. The “difference of spectra” technique was employed to separate the ISGDR from the high-energy octupole resonance (HEOR). These data provide the clearest evidence yet for the ISGDR adjacent to the HEOR. With these results, all expected isoscalar $\lambda \le 3$ resonances in ${}^{208}\mathrm{Pb}$ have been identified.

We present candidates for the global minimum energy solitons of charge 5 to 9 in the Skyrme model generated using sophisticated numerical algorithms. The solitons found are particularly symmetric; for example, the charge seven skyrmion has icosahedral symmetry, and the shapes are shown to fit a remarkable sequence defined by a geometric energy minimization (GEM) rule.

The Skyrme model of nuclear physics requires quantization if it is to match observed nuclear properties. A simple technique is used to find the normal mode spectrum of the baryon number $B=4\mathrm{}$ Skyrme soliton. We find 16 vibrational modes and classify them under the cubic symmetry group ${\mathrm{O}}_h$ of the static solution. The spectrum possesses a remarkable structure, with the lowest energy modes lying in those representations expected from an approximate correspondence between Skyrmions and Bogomolny-Prasad-Sommerfeld monopoles. The next mode up is the “breather”, and above that are higher multipole breathing modes.

Emission probability of bremsstrahlung in the $\alpha$ decay of ${}^{210}\mathrm{Po}$ was measured in $\alpha$- $\gamma$ coincidence measurements with Si and Ge detectors. It was found that the bremsstrahlung yields are much smaller than those predicted by a Coulomb acceleration model, in which $\gamma$ rays are emitted during acceleration outside the barrier. This suggests that the radiation amplitude in the barrier cannot be neglected, and the discussion based on a quasiclassical approach is given.

A magneto-optic trap (MOT) can provide a well-polarized, backing-free, localized source of radioactive atoms for $\beta$-decay experiments. We have trapped approximately 6000 atoms of ${}^{38}{\mathrm{K}}^m$ ( $t_{1/2}=0.925\mathrm{}\mathrm{s}$) and 2000 atoms of ${}^{37}\mathrm{K}$ (1.226 s) produced at the TRIUMF on-line separator TISOL in a vapor-cell MOT. We have measured optical isotope shifts and deduced the nuclear charge radii, which show an unusual lack of change at the neutron number $N=20\mathrm{}$ shell closure. Plans include a search for scalar contributions to the ${\beta }^{+}$- $\nu$ correlation in the $0^{+}\to 0^{+}$ decay of ${}^{38}{\mathrm{K}}^m$.

Peripheral fragmentation of a 240 MeV/nucleon beam of the halo nucleus ${}^6\mathrm{He}$ incident on carbon target has been studied in a kinematically complete experiment. It is found that one-neutron stripping to the unbound nucleus ${}^5\mathrm{He}$ is the dominant fragmentation mechanism and that it leads to a spin alignment of ${}^5\mathrm{He}$ in a plane perpendicular to the ${}^5\mathrm{He}$ momentum vector. This is expected to be a common feature for all neutron halo nuclei.

It is found that energy correlations within the bands of the good rotor odd- $A$ nuclei are well described by an anharmonic vibrator formula, which indicates an unexpected constancy of the moment of inertia. Based on a large collection of quasibands in all collective even-even and odd- $A$ nuclei, an empirical recurrence relation is proposed which allows one to calculate the excitation energies of any band starting from its lowest two. This simple two-parameter formula can be reduced approximately to that of a second order anharmonic vibrator.

The reaction ${}^{16}\mathrm{O}\left({e,e}^{\prime }\mathrm{pp}\right)$ has been studied at a transferred four-momentum $(\omega ,|\mathbf{q}|)=(210\mathrm{MeV},300\mathrm{}\mathrm{MeV}/c)$. Evidence has been obtained for direct knockout of proton pairs from the 1p shell. The excitation-energy spectrum of the residual nucleus and the missing-momentum densities indicate that knockout of a ${}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}$ pair dominates the reaction, while there is also a noticeable contribution from knockout of ${}^{3}P$ pairs.

We present new break-up and coherent data for $\eta$ meson photoproduction on the deuteron, using a deuterium target and tagged bremsstrahlung photons up to 1 GeV. The differential cross sections for the coherent process were measured from threshold to 800 MeV. They are much smaller than those previously reported. The break-up channel provides a direct measurement of the neutron to proton differential cross section ratios. At the $S_{11}\left(1535\right)$ resonance peak, ${\sigma }_n/{\sigma }_p=0.68\mathrm{}\pm 0.06$ leading to an isoscalar to isovector amplitude ratio of $A_s{/A}_{\upsilon }=0.096\mathrm{}\pm 0.02$.

High-precision mass measurements of proton-rich isotopes in the range of $60\le Z\le 84$ were performed using the novel technique of Schottky spectrometry. Projectile fragments produced by ${}^{209}$Bi ions at 930A MeV were separated with the magnetic spectrometer FRS and stored and cooled in the experimental storage ring (ESR). A typical mass resolving power of 350 000 and a precision of 100 keV were achieved in the region $A\approx 200$. Masses of members of $\alpha$ chains linked by precise $Q_{\alpha }$ values but not yet connected to the known masses were determined. In this way it is concluded that ${}^{201}$Fr and ${}^{197}$At are proton unbound.

The $\left({n,n}^{\prime }\gamma \right)$ reaction has been used to search for two-phonon $\gamma$-vibrational states in ${}^{166}\mathrm{Er}$. Levels at 1943 and 2028 keV have been observed with collective transitions to the $\gamma$ band. The latter, which has $B(E2;2028\mathrm{}\to 2_{\gamma }^{+})=7.4\mathrm{}\pm 2.5$ W.u. (Weisskopf unit) is interpreted as the ${I,K}^{\pi }{=4,4\mathrm{}}^{+}$ two- $\gamma$-phonon state. The former, for which the data indicate spin 0, has $B(E2;1943\mathrm{}\to 2_{\gamma }^{+})=21\mathrm{}\pm 6$ W.u. and is interpreted as the ${I,K}^{\pi }{=0,0\mathrm{}}^{+}$ two- $\gamma$-phonon state. This is the first observation of the $K^{\pi }{=0\mathrm{}}^{+}$ two- $\gamma$-phonon state in a well-deformed nucleus, and its identification places stringent limits on the nuclear models.

A microscopic description of heavy-cluster decay using a single particle basis suited to describe the continuum part of the spectrum is presented. The role of pairing correlations and quadrupole deformations is analyzed. The stability of the results as a function of the number of major shells included in the calculation is attested.

The spectrum of excited states in the hypernucleus ${}_{\Lambda }^{13}\mathrm{C}$ was studied at the Brookhaven Alternate Gradient Synchrotron using the $(K^{-},{\pi }^{-})$ reaction on an enriched ${}^{13}\mathrm{C}$ target. $\gamma$ rays coincident with the $p_{1/2\Lambda }$ state were observed using two large sodium iodide detectors. We interpret them as arising from the $p_{1/2\Lambda }\to s_{1/2\Lambda }$ transition in ${}_{\Lambda }^{13}\mathrm{C}$. This represents the first direct observation of a $\gamma$ ray associated with the transition of a hyperon between major nuclear shells.

Put forward more than three decades ago as an alternative to conventional shell-model calculations, the Kerman-Klein method has proved feasible previously only when applied to unrealistically small configuration spaces or when phenomenological simplifications have been superposed. Starting from a spherical shell-model Hamiltonian, we describe a fully microscopic calculation, free of the above limitations, of the properties of the ground-state band of a typical deformed rare-earth nucleus, ${}^{158}$Gd.

Parity-even time reversal violation (TRV) in the nucleon-nucleon interaction is reconsidered. The TRV $\rho$-exchange interaction on which recent analyses of measurements are based is necessarily also charge symmetry breaking (CSB). Limits on its strength ${\overline{g}}_{\rho }$ relative to regular $\rho$ exchange are extracted from recent CSB experiments in neutron-proton scattering. The result ${\overline{g}}_{\rho }\le 6.7\times {10}^{-3\mathrm{}}$ (95% C.L.) is considerably lower than limits inferred from direct TRV tests in nuclear processes. Properties of $a_1$ exchange and limit imposed by the neutron electric dipole moment are briefly discussed.

Transverse flow has been studied as a function of impact parameter for pions and protons from the reaction $1.15A\mathrm{GeV}$ ${}^{197}\mathrm{Au}{+}^{197}\mathrm{Au}$. We observe an “antiflow” behavior for both ${\pi }^{+}$ and ${\pi }^{-}$ in peripheral collisions.