The rare-earth crystal structure sequence ${\mathrm{hcp}}^{\to }$ Sm-${\mathrm{type}}^{\to }$ double-${\mathrm{hcp}}^{\to }$ fcc observed for decreasing atomic number and increasing pressure is quantitatively correlated with the $d$-band occupancy through the $d$-band energy contribution to the total energy. Self-consistent calculations show that the number of $d$ electrons is very sensitive to the relative size of the ion core. The theory thus accounts for La's anomalous double-hcp structure and the apparent deviations from the electron-per-atom rules exhibited by certain rare-earth Laves phases.

The phase transition near the percolation threshold in an Ising model with random exchange is investigated. The mean-field theory of the transition is discussed. The cross-over exponent $\varphi$ and susceptibility are caluclated in $6-\epsilon$ dimensions using renormalization-group methods with the result $\varphi =1+O\left({\epsilon }^3\right)$. $\varphi$ is also shown to be 1 near one dimension.

An exactly solvable model for relativistic two-body interaction, consisting of two harmonic oscillators coupled via a massless scalar field is studied. It is shown that prescribing the asymptotic field does not lead to a normal Cauchy problem for the particles, whereas the formulation as a Cauchy problem for particle and field is consistent. Radiation damping of the system is also discussed.

A 680-kg, Weber-type, cylindrical, gravitational-wave detector has been operated at liquid helium temperature. The average vibrational energy in the lowest longitudinal mode at 1315.3 Hz was found to be consistent with the level of thermal noise at the antenna temperature. An effective noise temperature of 0.39 K for pulse excitation was measured. This is a factor of 20 below the lowest published values for room-temperature detectors.

We trigger a large-acceptance spectrometer by single muons and observe any additional muons with good efficiency. The effect of $\pi$ and $K$ decays is subtracted to obtain the prompt muon signal in the kinematic region $0.1<x<\mathrm{}0.4\mathrm{}$ and $p_T<1.0\mathrm{}$ GeV/c. We find 0.7 ± 0.2 of all prompt $\mu \text{'}\mathrm{s}$ are produced in pairs; the $\frac{\mu }{\pi }$ ratio decreases with $x$ but increases with $p_T$, averaging 3 × ${10}^{-5\mathrm{}}$.

A field-theoretic parton model is considered, using an exactly renormalizable field theory without a transverse-momentum cutoff. The probability to find a parton with large transverse momentum is controlled by the light-cone behavior of products of field operators. As a result, the cross section to produce massive $\mu$ pairs in hadron collisions is predicted to contain terms that fall off only as ${\left|{\overrightarrow{\mathrm{Q}}}_T\right|}^{-2\mathrm{}}$ and ${\left|{\overrightarrow{\mathrm{Q}}}_T\right|}^{-4\mathrm{}}$.

We report on a new measurement of the time-reversal-violating triple angular correlation between the nuclear spin and the positron and neutrino directions $D\hat{J}·({\overrightarrow{\mathrm{v}}}_{\beta }\times {\hat{q}}_{\nu })$. Our result for the decay process ${}_{}{}^{19}{}_{}{}^{}\mathrm{Ne}\to {}_{}{}^{19}{}_{}{}^{}\mathrm{Fe}_{}^{-}{}_{}{}^{}+e^{+}+\nu$ is $D=-0.0005\mathrm{}\pm 0.0010$, consistent with time-reversal symmetry.

Proton polarization in $\gamma d\to \mathrm{pn}$ has been measured at c.m. angle around 90° and photon energies from 325 to 725 MeV. The polarization increases sharply with the photon energy, reaching a high maximum of (-80±8)% around 500-550 MeV. Such a high polarization with a sharp energy dependence seems to indicate a new effect in the dibaryon system.

Being motivated by the observation of an anomaly in the polarization of protons in $\gamma d\to \mathrm{pn}$, we have investigated the possible existence of deeply bound dibaryon states. The nonrelativistic one-boson-exchange potential model ($\pi$, $\eta$, $\rho$, and $\omega$ exchanges) for two $\Delta$ isobars gives binding energies around 100 MeV for $I=0\mathrm{}$, $J=3\mathrm{}$, and $I=3\mathrm{}$, $J=0\mathrm{}$. Existence of this $I=0\mathrm{}$ dibaryon resonance reproduces experimentally observed cross sections in the $I=0\mathrm{}$, $\mathrm{NN}\to d\pi \pi$ and $\mathrm{NN}\to \mathrm{NN}\pi \pi$ channels.

The elastic scattering and one-proton transfer reactions induced by 312.6-MeV ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ ions on ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ are investigated and compared with data at lower incident energies. A conventional distorted-wave Born approximation analysis can account for the qualitative features of the energy spectra but overestimates the energy dependence of the observed absolute cross sections by almost an order of magnitude between 140 and 312.6 MeV.

The background contribution to recently reported proton-induced x-ray spectra from selected monazite has been reevaluated in a systematic manner. The anomalies persist above both the background and the contribution from the reaction ${}_{}{}^{140}{}_{}{}^{}\mathrm{Ce}(p, n\gamma )$.

A tunable 5-μm spin-flip Raman laser and a carbon monoxide laser were used in a narrow wave guide to perform multiphoton absorption spectroscopy in NO. Coherent two-photon Doppler-free absorption and stepwise multiphoton absorption were observed. From this data the $\Lambda$-doubling constants $p$ and $q$ are found to have a vibrational dependence of $\Delta p=-2.2\mathrm{}\pm 1.0$ MHz and $\Delta q=-0.12\mathrm{}\pm 0.1$ MHz. The use of a wave guide has made it possible to obtain high intensities over long interaction lengths necessary for the experiment.

We point out that the $K\alpha$ satellite spectra of Al target x rays exhibit strong polarizazation in ion-atom collisions. The $K{\alpha }^{\prime } ({}_{}{}^1{}_{}{}^{}P_1^{}{}_{}{}^{}\to {}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{})$, $K{\alpha }_3 ({}_{}{}^3{}_{}{}^{}P_{2,1,0}^{}{}_{}{}^{}\to {}_{}{}^3{}_{}{}^{}P_{2,1,0}^{}{}_{}{}^{})$, and the $K{\alpha }_4 ({}_{}{}^1{}_{}{}^{}P_1^{}{}_{}{}^{}\to {}_{}{}^1{}_{}{}^{}D_2^{}{}_{}{}^{})$ transitions are, respectively, (+52 ± 5)%, (-9 ± 5)%, and (+9 ± 5)% linearly polarized following 1.9-MeV ${\mathrm{He}}^{+}$ bombardment and (+28 ± 5)%, (-6 ± 5)%, and (+6 ± 5)% linearly polarized following 1.9-MeV ${\mathrm{H}}^{+}$ bombardment.

The results of a new calculation of the $O\left(\alpha \right)$ corrections to the decay rate of orthopositronium are presented. The rate is $\Gamma ={\Gamma }^0[1-(\frac{\alpha }{\pi }\left)\right(10.348\mathrm{}\pm 0.070\left)\right]=(7.0379\pm 0.0012)\times {10}^6$ ${\sec }^{-1\mathrm{}}$. This is substantially below all measured rates as well as previous theoretical estimates. We provide further justification for the computational techniques employed.

Electron temperature perturbations produced by internal disruptions in the center of the Oak Ridge Tokamak (ORMAK) are followed with a multichord soft-x-ray detector array. The space-time evolution is found to be diffusive in character, but the conduction coefficient determined from a heat-pulse-propagation model is larger by a factor of 2.5-15 than that implied by the measured gross energy-containment time.

A simple formula is derived for the static magnetic field generated by resonance absorption of light in an inhomogeneous plasma. It is shown that this field evolves adiabatically in time with the high-frequency-wave amplitudes and that steady state is achieved by a balance between radiation-induced stresses and frictional or convective losses, the latter effects having been neglected in all previous work on this subject. Comparison is made with computer simulation and experiment.

A self-consistent three-dimensional nonlinear Schrödinger equation is derived for dispersive media such as plasmas by using the Krylov-Bogoliubov-Mitropolsky multiple space-time method. The necessary and sufficient conditions for the occurrence of modulational instability and the collapse of Langmuir as well as ion-acoustic waves are obtained. In weakly turbulent systems, collapse is not possible.

The heat capacity of the ordering transition of helium films is studied on a new graphite substrate whose microcrystallite allignment and lateral size are ten times that for Grafoil. Transition peaks are considerably sharper than those observed on Grafoil allowing determination of critical parameters $\alpha \cong 0.36$ and $\frac{A^{+}}{A^{-}}\cong 0.65$. The $\alpha$ is substantially larger than recent three-state Potts-model calculations in two dimensions (of which the ordering transition is the only example), raising the possibility that the ordered state belongs to a new university class.

We compute up to order ${\epsilon }^2$ all dynamics transients (subleading exponents) for helium and symmetric antiferromagnets. We also discuss the relevance for helium of a fixed point which leads to a "weak" dynamic scaling.

The characteristic dissipation process for conventional superfluid flow is phase slip-page: motion of quantized vortices in response to the Magnus force, which allows finite chemical potential differences to occur. Topological considerations and actual construction are used to show that in liquid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-$A$, textures with vorticity but no vortex core can easily be constructed, so that dissipation of superfluid flow can occur by motion of textures alone without true vortex lines, dissipation occurring via the Cross viscosity for motions of $\hat{l}$.