A continuous wave dye laser and a thermal atomic beam were used to measure the optical isotope shifts and hyperfine splittings for the 5547 Å, 5639 Å, 5652 Å, 5974 Å, and the 5989 Å transition of the seven stable isotopes of dysprosium. The hyperfine splitting of the odd-$A$ isotopes has been analyzed using the formalism of Sanders and Beck and the hyperfine anomaly has been extracted. Comparison with calculations using Nilsson wave functions is presented. The isotope shift measurements have been analyzed with published electronic and muonic x-ray isotope shifts to yield $\delta 〈r^2〉$ values and some estimates of the specific mass shift constant.

NUCLEAR STRUCTURE ${}_{}{}^{156-164}{}_{}{}^{}\mathrm{Dy}$. Measured optical isotope shifts and hyperfine splittings. Deduced $\delta 〈r^2〉$, $A\left(4\mathrm{}{f}^{12}6s6p\right)$, $B\left(4\mathrm{}{f}^{12}6s6p\right)$, and the hyperfine anomaly. Laser spectroscopy on atomic beams.

Compression modes are characterized as volume oscillations of the nucleus which do not contribute to the photonuclear sum rule but show up as concentrated strength in, e.g., inelastic hadronic scattering. Comparison of the nuclear response to different operators in the frame of a continuum random phase approximation is the theoretical technique used to search for such compression modes. Sharply concentrated strength is found only for the breathing mode and the isoscalar dipole mode. Large widths are expected for the isovector monopole, the isovector dipole compression mode, and the isoscalar quadrupole compression mode. For those modes whose escape width corresponds to a large fraction of the total width, one suggests the possibility of detecting them in coincidence experiments by observation of the decaying particle.

NUCLEAR STRUCTURE ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$; calculated compression mode sum rule strength. Random phase method, Landau-Migdal interaction.

We present a method for calculating matrix elements for a shell model Hamiltonian in the truncated shell model space of the interacting boson model for the case where the pairs are distributed with unequal amplitudes over several nondegenerate $j$ orbits. Explicit formulas are presented for generalized seniority zero and two.

NUCLEAR STRUCTURE Microscopic theory of the interacting boson model.

The long-mean-free path nuclear fluid dynamics is extended to include damping. First the damping stress is derived from the solution of the Boltzmann equation for a breathing spherical container filled with a Fermi gas. Then the corresponding damping force is incorporated into Euler equations of motion and energies and widths of low lying collective resonances are computed as eigenfrequencies of a vibrating nucleus under surface tension and Coulomb potential as well as the high lying isoscalar giant resonances as eigenfrequencies of an elastic nucleus. Maximum damping is obtained if the particle frequency approximately resonates with the wall frequency. Theoretical results are compared with experimental data and future improvements are indicated.

NUCLEAR STRUCTURE Nuclear giant resonances; calculated widths of isoscalar giant resonances. Elastic vibrations, Boltzmann equation, collision term, long-mean-free path dissipation.

The particle-rotor model with a single nucleon in a configuration with large fixed $j$ is treated by means of the Holstein-Primakoff expansion. The small-oscillation approximation yields relatively simple analytic expressions for energies, alignments, electromagnetic moments, and transition rates of decoupled bands, which are surprisingly accurate over a broad range of $\frac{C}{A}$.

NUCLEAR STRUCTURE Particle-rotor model; approximate analytic formulas; Holstein-Primakoff boson expansion.

Number-projected quasiparticles calculations in the heavy $N=82\mathrm{}$ isotones with $62\le Z\le 68$ have been performed. We discuss in some detail the results obtained for the energy spectra and electromagnetic decay properties of the even-mass isotones ${}_{}{}^{144}{}_{}{}^{}\mathrm{Sm}$, ${}_{}{}^{146}{}_{}{}^{}\mathrm{Gd}$, ${}_{}{}^{148}{}_{}{}^{}\mathrm{Dy}$, and ${}_{}{}^{150}{}_{}{}^{}\mathrm{Er}$ and the odd-mass isotones ${}_{}{}^{145}{}_{}{}^{}\mathrm{Eu}$, ${}_{}{}^{147}{}_{}{}^{}\mathrm{Tb}$, ${}_{}{}^{149}{}_{}{}^{}\mathrm{Ho}$, and ${}_{}{}^{151}{}_{}{}^{}\mathrm{Tm}$ and compare them with the results of a seniority-model calculation.

NUCLEAR STRUCTURE Projected quasiparticles calculations. Heavy $N=82\mathrm{}$ nuclei with $62\le Z\le 68$. Energy spectra and electromagnetic decay properties.

The magnetic moment of the ground state of ${}_{}{}^{114}{}_{}{}^{}\mathrm{In}$ is determined as $2.817\left(11\right)\mathrm{} {\mu }_N$ using nuclear magnetic resonance on oriented nuclei. The implantation behavior of ${}_{}{}^{114}{}_{}{}^{}\mathrm{In}$ is discussed. A discussion and relation to nuclear structure is given for the magnetic moment.

NUCLEAR STRUCTURE ${}_{}{}^{114}{}_{}{}^{}\mathrm{In}$: isotope separation, implantation in Fe. NMR/ON: Si(Li) and Ge(Li) detectors. Measured $A_1$, $\mu$. Calculation configuration mixing theory.

The possibilities for the backbending effect to occur in actinide nuclei are studied using the pairing-self-consistent independent quasiparticle method. The Hamiltonian used is that of the deformed Woods-Saxon potential plus monopole pairing term. The results of the calculations explain why there is no backbending in most actinide nuclei and simultaneously suggest that in some light neutron deficient nuclei around ${}_{}{}^{224}{}_{}{}^{}\mathrm{Th}$ and ${}_{}{}^{22}{}_{}{}^{}\mathrm{Ra}$ a backbending effect may occur.

NUCLEAR STRUCTURE Collective structure in levels (including rotational bands); collective models.

The Woods-Saxon potential is employed to interpret the properties of single particle and high spin spectra of ${}_{}{}^{146}{}_{}{}^{}\mathrm{Gd}$. Spin orbit potential parameters are found which simultaneously reproduce the experimental yrast and yrare states up to $I\sim 18$ and generate the proton single particle energy gap ${\delta }_p=2.0\mathrm{}$ MeV. The spin-orbit potential parameters obtained are nearly identical for neutrons and protons and are close to the parameter values obtained previously by optimizing the potential to high spin spectra in the vicinity of ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$. Properties of the pairing correction method, the Bardeen-Cooper-Schrieffer approximation with blocking, and the particle number projection are discussed and illustrated. It is demonstrated that including the particle number projection term in the total energy formula improves considerably the average slope of the calculated yrast line. The possibility of the collective quadrupole vibrational states becoming yrast states is studied for $I\gtrsim 7\hslash$ using the random phase approximation but only a rather weak effect of collectivity is found in the spin-range studied.

NUCLEAR STRUCTURE ${}_{}{}^{146}{}_{}{}^{}\mathrm{Gd}$; Woods-Saxon single-particle levels, high spin excitations. Collectivity in the high spin states, RPA.

The idea that ${}_{\Lambda }{}^{12}{}_{}{}^{}\mathrm{C}_{}^{*}{}_{}{}^{}$ is a strangeness analog state is examined using the alpha particle model. Volkov, Gillet, and Brink-Boeker potentials are used for the nucleon-nucleon and lambda-nucleon interactions, to calculate the binding energies of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ and ${}_{\Lambda }{}^{12}{}_{}{}^{}\mathrm{C}_{}^{*}{}_{}{}^{}$. ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ is described by an equilateral triangle. When an allowance is made for the exchange character of the potentials used, the required potential strengths seem to be consistent with those obtained from low energy and light hypernuclear data, thus supporting the idea of a strangeness analog state.

NUCLEAR STRUCTURE ${}_{\Lambda }{}^{12}{}_{}{}^{}\mathrm{C}_{}^{*}{}_{}{}^{}$, binding energy calculated assuming strangeness analog state in alpha particle model.

The effect of angular momentum and parity projection on the energy and deformation of the oblate and prolate minimum in ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ has been studied. We discuss the approximations resulting from variation without, before, and after projection for a number of standard nucleon-nucleon interactions. We find that the intrinsic oblate and prolate minimum occur in reversed energetical order for most forces. The effect of angular momentum projection alone tends to resolve the discrepancy but this effect is reduced if the projected states are allowed to vary.

NUCLEAR STRUCTURE ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$; alpha-cluster model variation after projection with finite-range forces. Calculated energies, quadrupole moments, rms radii.

The differential cross sections for the excitation of giant resonances in ${}_{}{}^{92}{}_{}{}^{}\mathrm{Zr}$ have been measured in the angular range 14 to 30° by inelastic scattering of 115 MeV protons. The low energy octupole region $E_x=5-10.5\mathrm{}$ MeV can be explained as due to excitation of $L=3\mathrm{}$ and $L=4\mathrm{}$ multipoles. The composition of the differential cross section for the giant resonance region ($E_x\simeq 10.5-20$ MeV) can be described in terms of the percentage energy-weighted sum-rule strength as ≃ 63% giant monopole resonance, ≃ 65% giant dipole resonance, ≃ 48% giant quadrupole resonance, and ≃ 20% $L=4\mathrm{}$ resonance.

NUCLEAR REACTIONS ${}_{}{}^{92}{}_{}{}^{}\mathrm{Zr}(p, p^{\prime })$, $E_p=115\mathrm{}$ MeV; measured $\sigma \left(\theta \right)$ for giant resonance excitation; calculated the percentage energy-weighted sum-rule strengths for $L=0\mathrm{} \mathrm{to} 4$ multipoles.

Cross sections for the primary pion beam monitor reactions ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}({\pi }^{\pm }, \pi N){}_{}{}^{11}{}_{}{}^{}\mathrm{C}$ (20.4 min) have been measured between 30 and 100 MeV by activation techniques. These cross sections are consistently lower, but within the uncertainties of our previously determined values. The experimental uncertainties of these new measurements are considerably smaller.

NUCLEAR REACTIONS ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}({\pi }^{\pm }, \pi N){}_{}{}^{11}{}_{}{}^{}\mathrm{C}$ measured cross sections by activation, $T_{\pi }=30-100\mathrm{}$ MeV. Plastic scintillator targets; pion flux determined with scintillator telescope.

Levels of ${}_{}{}^{83}{}_{}{}^{}\mathrm{Rb}$ and ${}_{}{}^{86}{}_{}{}^{}\mathrm{Rb}$ have been populated by bombarding natural krypton gas with protons of $E_p=2830\mathrm{}$ keV. Doppler shift attenuation measurements in gas were performed using the same krypton gas as stopper medium. Lifetimes or lifetime limits are determined for four levels in ${}_{}{}^{83}{}_{}{}^{}\mathrm{Rb}$ and for the first excited level in ${}_{}{}^{86}{}_{}{}^{}\mathrm{Rb}$. The collective properties of positive parity states in ${}_{}{}^{83}{}_{}{}^{}\mathrm{Rb}$ are confirmed.

NUCLEAR REACTIONS ${}_{}{}^{82}{}_{}{}^{}\mathrm{Kr}(p, \gamma )$, ${}_{}{}^{83}{}_{}{}^{}\mathrm{Kr}(p, n)$, ${}_{}{}^{86}{}_{}{}^{}\mathrm{Kr}(p, n)$, $E_p=2.8\mathrm{}$ MeV. Natural krypton gas target; $p={10}^4-{10}^7$ Pa. Doppler shift attenuation in gas. Measured: $\gamma$ transition energies, lifetimes.

An isospin coupled-channels analysis of sub-Coulomb-proton-absorption cross sections has been performed for ${}_{}{}^{92,94,96}{}_{}{}^{}\mathrm{Zr}$ and ${}_{}{}^{94,96,98,100}{}_{}{}^{}\mathrm{Mo}$. Introduction of coupling to the channel consisting of a neutron plus the isobaric analog of the target is shown to shift and damp the single-particle resonances, in addition to giving rise to isobaric-analog resonances. In spite of these effects due to the coupling, large variations in the absorptive potentials were still required to fit measured ($p, n$) cross sections. ${}_{}{}^{96}{}_{}{}^{}\mathrm{Zr}(p, n)$ and ${}_{}{}^{100}{}_{}{}^{}\mathrm{Mo}(p, n)$ cross sections were measured and analyzed with a standard optical model for this work. Other $\mathrm{Zr}(p, n)$ and $\mathrm{Mo}(p, n)$ cross sections were taken from previous results.

NUCLEAR REACTIONS ${}_{}{}^{96}{}_{}{}^{}\mathrm{Zr}$, ${}_{}{}^{100}{}_{}{}^{}\mathrm{Mo}(p, n)$; $E_p=2.0-6.5\mathrm{}$ MeV; measured total $\sigma \mathrm{}\left(E\right)\mathrm{}$. Lane-model coupled channels analysis ${}_{}{}^{92,94,96}{}_{}{}^{}\mathrm{Zr}$ and ${}_{}{}^{94,96,98,100}{}_{}{}^{}\mathrm{Mo}$ proton-absorption cross sections, deduced absorptive potential strengths.

Lifetimes of states of ${}_{}{}^{72}{}_{}{}^{}\mathrm{Br}$ produced by the reaction ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}({}_{}{}^{16}{}_{}{}^{}\mathrm{O}, np)$ have been measured by the recoil-distance Doppler-shift method. The transition rates deduced for the 353.3, 323.2, and 270.0 keV transitions are 66(15), 125(40), and 79(35) single particle units, respectively. The identification of the levels, deexcited by these transitions, as member of the $\pi g_{\frac{9}{2}}\otimes \nu g_{\frac{9}{2}}$ structure is discussed.

NUCLEAR REACTIONS ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}({}_{}{}^{16}{}_{}{}^{}\mathrm{O}, np)$ $E=50\mathrm{}$ MeV; measured Doppler shift, deduced, $T_{\frac{1}{2}}$.

The mean life of the $J^{\pi }=5^{-}$, $T=0\mathrm{}$ state at 4848 keV in ${}_{}{}^{18}{}_{}{}^{}\mathrm{F}$ has been measured to be 5.2±0.9 ps via the recoil-distance method. The corresponding $E2\mathrm{}$ transition strength of 14.8±2.6 Weisskopf units for decay to the $3^{-}$ level at 3791 keV establishes a strongly collective transition.

NUCLEAR REACTIONS ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}({}_{}{}^{11}{}_{}{}^{}\mathrm{B}, \alpha n){}_{}{}^{18}{}_{}{}^{}\mathrm{F}$, $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}=16.7\mathrm{}$ MeV; measured mean life of 4848-keV level; deduced transition strengths; recoil-distance method, Ge(Li) detector.

We have observed narrow nuclear magnetic resonances in polarized ${}_{}{}^{19}{}_{}{}^{}\mathrm{Ne}$ stored for several seconds in a Formvar cell. The nuclear polarization is monitored by observing the $\beta$-decay asymmetry while the atoms are subjected to an rf driving field. Due to the long observation times and motional averaging, narrow resonance widths are observed. Using this technique we find $\mu \left({}_{}{}^{19}{}_{}{}^{}\mathrm{Ne}\right)=-1.885\mathrm{}42\left(8\right)\mathrm{}{\mu }_N$. Possible application to other radioactive noble gas isotopes is discussed.

NUCLEAR STRUCTURE ${}_{}{}^{19}{}_{}{}^{}\mathrm{Ne}$; measured $\mu$. Observed motional averaging. Magnetic field stabilizer.

Precision measurements of orbit sizes indicate that the root mean square radius decreases almost linearly as the particle separation energy increases at the rate $\frac{\partial r}{\partial \epsilon }=-0.08\mathrm{}$ fm Me${\mathrm{V}}^{-1\mathrm{}}$.

NUCLEAR STRUCTURE Systematics of orbit sizes, implication for mean field theories.

We have constructed three rank-one energy-independent separable potentials for the pion-nucleon $P_{33}$ channel which reproduce the scattering volume and phase shift up to 350 MeV. The amplitudes were calculated from these potentials using the Blankenbecler-Sugar equation approach and are appropriate for relativistic three-body calculations of the $\pi \mathrm{NN}$ system. An interesting feature of resulting potentials is the appearance of two very different ranges in each. The low-momentum parts of the different potentials are essentially the same but there are significant differences in their high-momentum behavior. Information from $\mathrm{NN}$ pion-production supports the two-range feature of these potentials and favors one of the potentials over the others.

NUCLEAR REACTIONS $N(\pi , \pi )N$; separable potentials for $P_{33}$ channel; calculated $\delta \mathrm{}\left(E\right)\mathrm{}$, $E=0-350\mathrm{}$ MeV.