The familiar minimum-uncertainty wave packets for masses are generalized in analogy with the two-photon coherent states of the radiation field. The free evolution of a subclass of these states, the contractive states, leads to a narrowing of the position uncertainty in contrast with the usual minimum-uncertainty wave packets. As a consequence the standard quantum limit for monitoring the positions of a free mass can be breached. Further implications on quantum nondemolition measurements are discussed.

A new and relatively simple method has been developed to focus and guide electron beams without the use of a magnetic field. The scheme relies on the electrostatic charging of a highly resistive wire in the presence of a beam. The beam is then strongly guided and focused by the oppositely charged wire. In addition, the highly anharmonic nature of the wire potential leads to rapid phase-mix damping of transverse beam displacements and radial pulsations.

The behavior of autocorrelation functions in a $K$ system (the stadium billiard) is studied, and the existence of long-time tails is demonstrated both analytically and numerically. The tails are shown to depend on the presence of arbitrary long segments of regular motion in the time evolution of the stochastic orbits. It is surmised that an analogous mechanism might be responsible for long-time tails in a large class of systems.

Results are presented from a search for fractional charges in water from a variety of natural sources. About 30 000 water drops have been measured, comprising 51 μg of water and dissolved materials. No evidence for fractional charge was seen.

The Fermilab 15-ft bubble chamber, filled with a heavy neon-hydrogen mix, was exposed to a narrow-band ${\nu }_{\mu }$ beam. Based on the observation of 830 charged-current ${\nu }_{\mu }$ interactions, the cross section was found consistent with a linear rise with the neutrino energy in the interval $10 \mathrm{GeV}<~E_{\nu }\lesssim 240 \mathrm{GeV}$. The average slope was determined to be $\frac{{\sigma }_{\nu }}{E_{\nu }}=(0.62\mathrm{}\pm 0.05)\times {10}^{-38\mathrm{}}$ ${\mathrm{cm}}^2$ ${\mathrm{GeV}}^{-1\mathrm{}}$.

The ${\overline{\nu }}_{\mu }$ charged-current total cross section has been measured with the Fermilab 15-ft bubble chamber plus the external muon identifier and internal "picket fence." Beam monitoring information used for the flux calculation was obtained from Blair et al., whose detector operated in the same dichromatic beam. The present result, averaged over ${\overline{\nu }}_{\mu }$ energies from 5 to 250 GeV, is $\frac{\sigma }{E}=(0.340\mathrm{}\pm 0.019\pm 0.022)\times {10}^{-38\mathrm{}}$ ${\mathrm{cm}}^2$/(GeV nucleon) for an isoscalar target.

The prompt ${\nu }_{\mu }$ and ${\overline{\nu }}_{\mu }$ flux produced by 400-GeV protons has been measured with a detector located 56 m from a tungsten target. The cross section for the hadronic production of charm is determined to be 27±4±5 μb/nucleon subject to the following assumptions: $D\overline{D}$ production only; $A^1$ variation of cross section; and a parametrization of the $D$-production cross section which is ${\mathrm{}(1-x)\mathrm{}}^4\exp (-2\mathrm{}{m}_{\perp })$. The ratio of prompt ${\overline{\nu }}_{\mu }$ flux to prompt ${\nu }_{\mu }$ is measured to be 1.12±0.24±0.17, consistent with predominantly $D\overline{D}$ production.

Furnishing Skyrme's chiral soliton with a quark-bag core appears to generate a qualitative advance in the phenomenology of nucleon structure.

Topologically stable solitonic solutions to Skyrme's chiral-invariant Lagrangian have been obtained numerically. The single parameter in these solutions has been determined with the Goldberger-Treiman relation. The identification of these objects with baryons leads to sensible statements regarding the sizes and energies of baryons as well as the two- and three-body interactions between baryons at zero separation.

It is shown that each isospin channel in the long-range approximation to the nucleon-nucleon potential (one-pion-exchange potential) corresponds to a realization of a quantum mechanical supersymmetric Hamiltonian. A functional relation between the coordinate-dependent coefficients of the spin-spin and tensor parts of the interaction predicted by supersymmetry is exactly fulfilled.

Precision measurements of the analyzing powers for the reaction $p_{\mathrm{pol}}+p\to d+{\pi }^{+}$ have been made at ≃ 550, 600, 650, 700, and 800 MeV. The data have been analyzed in terms of Legendre polynomials. It is found that excitation functions for both even and odd Legendre coefficients exhibit very similar resonant behaviors. It is concluded that the triplet amplitudes are as strongly dominated by the $\Delta \mathrm{}\left(1232\right)\mathrm{}$ as the well-known singlet amplitude, ${}_{}{}^1{}_{}{}^{}D_2^{}{}_{}{}^{}$, and that the data do not exhibit any anomalous behavior suggestive of dibaryon resonances.

The authors construct, in the static potential approximation, the number operator for excess pions present in nuclei due to the pion-exchange forces between nucleons. Expectation values are calculated with use of variational wave functions obtained from a realistic Hamiltonian. Results are presented for systems ranging from the deuteron to nuclear matter: For example ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}$ is estimated to have ∼7 extra pions, over and above the pion clouds associated with the individual nucleons.

As a result of photoionization of rare-gas atoms by x rays emitted from a laser-produced plasma, high densities (> ${10}^{16}$ ${\mathrm{cm}}^{-3\mathrm{}}$) of hot (∼ 45-eV) electrons are produced in a pulse of ∼600 ps duration. Following excitation by means of this electron source, the deexcitation rate constant from the $\mathrm{Li}\mathrm{}\left(1s2s2p\right)\mathrm{}{}_{}{}^4{}_{}{}^{}P°$ level is measured to be 3×${10}^{-7\mathrm{}}$ ${\mathrm{cm}}^3$ ${\mathrm{s}}^{-1\mathrm{}}$ at an electron density of ∼${10}^{15}$ ${\mathrm{cm}}^{-3\mathrm{}}$.

The hyperfine structure of high Rydberg states of ${}_{}{}^{87}{}_{}{}^{}\mathrm{Sr}$ was studied for principal quantum numbers $80<~n<~150$. The hyperfine interaction causes a strong singlet-triplet mixing between levels with the same total angular momenta $F$ but different quantum numbers $n$. Semiempirical calculations show excellent agreement with experiment.

A theory is presented for construction of sequences of phase-shifted radiation pulses for coherently inverting populations over a broad band of transition frequencies. Such sequences have applications in nuclear magnetic resonance and coherent optics. Examples of sequences are derived, together with computer simulations of their inversion properties.

A powerful calculational low-energy electron-diffraction scheme is introduced for super lattices with unit cells of any size: beam-set neglect. It is applied in the first structural analysis from low-energy electron-diffraction intensities of a large molecule, benzene, adsorbed on a single-crystal metal surface, Rh(111). In a $\left(\{3,1\}\{1,3\}\right)$ lattice, benzene is found to lie flat on the surface, centered over hcp-type hollow sites. A planar, possibly distorted ${\mathrm{C}}_6$ ring is found with Rh-C bond lengths of 2.35±0.05 Å.

In this Letter evidence is provided for a roughening transition in adsorbed xenon multilayers on palladium. The layer-distinctive Xe $5p$ photoemission is used to measure adsorption isotherms as well as the relative equilibrium population of individual Xe layers. Below the roughening temperature $T_R$ xenon adsorbs layer by layer. Above $T_R$ simultaneous population of different layers takes place.

A layer of nematic liquid crystal that has undergone an electrohydrodynamic instability (and contains nonequilibrium structures with period $l_0$) is subjected to a spatially periodic electric field with periodicity $l_1$. The competition between these two length scales is found to result in novel ordered phases similar to those found in equilibrium condensed-matter systems. A simple model is proposed that accounts for most of the observations.

Two-dimensional ${\mathrm{O}}_2$ physisorbed on graphite shows a structural and magnetic phase transition from the paramagnetic to the antiferromagnetic state. A high-resolution specific-heat measurement is presented which reveals that there are two successive phase transitions: first a three-state Potts transition, producing a distorted lattice being still paramagnetic, and second an elastically driven Ising transition from the paramagnetic to the antiferromagnetic state.

The existence of a surface roughening under far-from-equilibrium conditions is demonstrated. Roughening is critically controlled by surface kinetic processes, such as the atomic migration rate. Monte Carlo simulations are presented for a model of molecular-beam epitaxial growth of tetrahedrally bonded compound semiconductors. It is proposed that the roughening reported for GaAs/AlAs(100) growth, if intrinsic, corresponds to the kinetic surface roughening predicted here rather than that predicted by Burton, Cabrera, and Frank for surface-vapor equilibrium.