A set of classical variables associated with the interacting-boson model is defined. It is shown that these variables can be put in one-to-one correspondence with Bohr's liquid-drop variables. The classical equilibrium "shapes" corresponding to the three limits of the interacting-boson model are analyzed and the nature of the "shape" phase transitions between them is studied.

Neutron spectra from ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}(p, n){}_{}{}^{90}{}_{}{}^{}\mathrm{Nb}$ at $E_p=120\mathrm{}$ MeV are measured in the angular range 0°-25°. Three giant resonances are seen and are interpreted as the $T=4\mathrm{}$ and $T=5\mathrm{}$ components of the Gamow-Teller strength and an $E1\mathrm{}$ resonance. Gamow-Teller matrix elements are extracted, and a large part of the expected strength is found.

After simple corrections for distortion effects, 120-MeV, 0° ($p, n$) cross sections are found to be proportional to the squares of the corresponding Fermi and Gamow-Teller matrix elements extracted from $\beta$-decay measurements. It is suggested that this proportionality can be used to extract Gamow-Teller matrix elements for transitions inaccessible to $\beta$ decay.

Alpha particles (3.5 MeV) from the deuterium-tritium reaction have been calculated to reflect from a high-$Z$, Fermi-degenerate shell surrounding the fuel of inertial fusion targets. This leads to a reduction in the minimum fuel $\rho R$ (density-radius product) needed to sustain a thermonuclear burn, and possibly to a reduction of the minimum input energy required to achieve thermonuclear ignition.

This paper reports experimental evidence that a convective loss occurs in a low-density plasma subjected to the ion-cyclotron rf field of $m=\pm 1$ azimuthal mode which is conventionally employed. By utilization of an $m=+1\mathrm{}$ circularly polarized rf field produced with a multiphase rf source, the convective plasma loss is eliminated, which results in an improvement in heating efficiency by more than 70%.

Three-dimensional, electromagnetic computer simulations are presented showing the evolution of colliding columnar plasmas. The interaction leads to a spiral configuration during which radiation is emitted.

Studies of surface-enhanced Raman scattering from pyridine adsorbed on Ag surfaces in ultrahigh vacuum show a strong dependence on both surface roughness and pyridine coverage. The observation of enhancement (${10}^4$) for physisorbed pyridine multilayers in addition to the first molecular layer implies that the enhanced effect is electromagnetic rather than chemical in origin.

The enhanced Raman scattering from a molecule adsorbed on a metal surface is calculated by use of classical electrodynamics. The metal response function is modeled with a local interband term plus a nonlocal free-electron term. The important effects are the image enhancement of the effective dipole and the roughness coupling of the near fields of the dipole and its image. These combine to give estimated gains ≈ ${10}^6$.

The inverse-square distance dependence of the gravitational force has been tested over a range of approximately 2 to 5 cm, by use of a test mass suspended from a torsion balance to probe the gravitational field inside a mass tube. The result supports an inverse-square law. Assuming a force deviating from inverse square by a factor [$1+\epsilon \ln \gamma$ (cm)] it is found that $\epsilon =(1\mathrm{}\pm 7)\times {10}^{-5\mathrm{}}$.

It is found that some decays of bottom and top mesons, such as $B_s\to \varphi \varphi$, can proceed only via diagrams conjectured to play an important role in $\mathrm{CP}$ nonconservation, $\Delta I=\frac{1}{2}$ dominance, and Cabibbo-suppressed charmed-meson decays. These new decays are estimated and predictions are presented for charmed-meson decays. All predictions depend crucially on the relative importance of certain strong corrections to weak process (penguins).

This Letter demonstrates the importance of two reactions with high threshold-fission of nuclei around the lead region and high-multiplicity nucleon emission-in studying the high-energy tail of the nuclear response function in muon capture. Conventional impulse approaches and the recently proposed absorption model of the nonimpulse variety are shown to give significantly different yields for these reactions.

Data and calculations for ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}(p, p^{\prime }){}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ reactions at 122 MeV are discussed with respect to predictions and implications of precritical phenomena near pion-condensation thresholds. The evidence is largely unsupportive of the expectations of precritical behavior.

Threshold-energy peaks are observed for electron impact excitation of ${\mathrm{N}}_2$ and ${\mathrm{H}}_2$ to high-Rydberg states. These peaks are attributed to the direct excitation of high-$l$ states near threshold consistent with the prediction of Fano.

The results of double-laser experiments in which ${\mathrm{Na}}_2^{+}$ and ${\mathrm{Na}}^{+}$ are produced in crossed alkali beams under single-collision conditions in the presence of strong optical fields are reported. Structure in the mass-selected product ion intensity as a function laser frequency is observed when the optical field is strongly focused and tuned far off atomic or dimer transitions. These measurements are the first to show that the nuclear motion of the quasimolecular collision intermediate plays an important role in laser-induced collisional ionization.

The major disruption has been studied in detail on the TOSCA tokamak with the use of approximate helical coils. The $m=3\mathrm{}$, $n=2\mathrm{}$ and $m=5\mathrm{}$, $n=3\mathrm{}$ modes have been clearly observed for the first time before a major disruption. The amplitude of the $m=2\mathrm{}$, $n=1\mathrm{}$ mode at the rational surface is about 4% and the $m=3\mathrm{}$, $n=2\mathrm{}$ mode amplitude ∼ 4.5% before a major disruption. When the $m=2\mathrm{}$, $n=1\mathrm{}$ and $m=3\mathrm{}$, $n=2\mathrm{}$ approximate helical coils are energized with large coil currents, a major disruption occurs.

X-ray emission spectra, produced by irradiation of neon-filled aluminum-coated glass microballoon and plane aluminum targets, with 100-ps Nd-glass laser pulses, have been time resolved with an x-ray streak camera. The time evolution of the $\mathrm{Ne}\times L\alpha$ and Si xiii $1{}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}-3\mathrm{}{}_{}{}^1{}_{}{}^{}P_1^{}{}_{}{}^{}$ linewidths has been recorded. The implosion delay time of microballoon targets and the emission histories of the Al xiii $1{}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}-2\mathrm{}{}_{}{}^1{}_{}{}^{}P_1^{}{}_{}{}^{}$ line and its satellites from plane targets have been measured.

Polymer-coated glass microspheres filled with DT fuel and argon seed gas were irradiated with the SHIVA 1.06-μm laser using 4-kJ, 200-ps (full width at half maximum), Gaussian pulses. Measured light absorption, x-ray spectrum, neutron yields, and x-ray continuum images compared favorably with detailed computer simulations. Pusher neutron activation and argon line imaging diagnostics were utilized to measure fuel density. Fuel densities of 1-3 g/${\mathrm{cm}}^3$ or 5-15 times liquid DT density were inferred.

In the rotamak concept, a rotating magnetic field is used to drive the toroidal current in a compact torus device. A rotamak device is described and initial experimental results are presented. Toroidal currents in the range 6-10 kA have been produced. Magnetic probe and power measurements, together with zero-dimensional, time-dependent plasma model calculations, indicate that a compact torus configuration has been generated for which the Ohmic power input is balanced by line radiation.

With use of bromine atoms, deposited on the surface of a silicon single crystal, the presence of x-ray standing waves above the crystal surface has been detected under conditions of strong Bragg diffraction.

A model for the reconstructions of the W(100) surface is presented. Four types of distortions are obtained, along $〈011〉$, $〈001〉$, $〈100〉$ (commensurate), and (× 10) (incommensurate). The $〈011〉$ distortion, corresponding to the observed $(\sqrt{2}\times \sqrt{2})45\mathrm{}°$ clean surface, is worked out in detail. A distortion magnitude of ∼ 0.35 Å is found, and a surface coherence length $\xi \simeq 15°$ Å close to experiment. The full vibrational spectrum, the distortion penetration, and the anisotropic surface anharmonic energies are also obtained.