We have made detailed measurements of the effective viscosity of dilute ${\mathrm{He}}^3$-${\mathrm{He}}^4$ solutions between 20 mK and 1 K, by observation of the damping of torsional oscillations of a quartz crystal. The results are strikingly different, in magnitude and in temperature dependence, from theoretical predictions and from previous preliminary results.

Quasielastic light-scattering studies from a solution of 1-μm-diam polystyrene spheres indicate that at sufficient dilution the homodyne autocorrelation function is not consistent with the common assumption that the concentration fluctuations are Gaussian stochastic processes. In this note we show that the non-Gaussian behavior at low concentrations arises because the particles in the scattering volume are Poisson distributed.

Measurements of the turbidity and of the intensity of light scattered by a cyclohexane-aniline mixture in the vicinity of the critical point allow us to verify that scaling laws correctly describe the observed phenomena and yield precise values of the critical exponents $\gamma$, $\nu$, and $\eta$, of the correlation length $\xi$, and of ${\left(\frac{\partial \mu }{\partial c}\right)}_{P,T}$.

A theory is presented for the nonlinearly saturated levels of Langmuir and acoustic waves produced by parametric instabilities. The theory accounts for the perturbation of particle orbits by waves. The results are quantitatively compared with recent simulations by Kruer and Dawson.

We investigate the effects of temperature gradient and magnetic shear on the radial dependence of the collisional trapped-particle mode. The former produces a reflecting layer at the edge of the plasma, while the latter introduces fine structure in the untrapped-particle terms. It is concluded, contrary to a published result, that unstable eigenmodes are likely to occur in large Tokamaks. Untrapped-ion resonances near the rational flux surfaces provided a stabilizing effect, however.

X-ray photoemission spectroscopy has been used to measure the valence band of CuNi alloys. The results are in good agreement with theoretical predictions based on the coherent-potential approximation.

We report the first observation of a ${\Gamma }_8$ (quartet) resonance in a metal (Au:Dy). The field for resonance determines the relative magnitude and sign of the crystal-field parameters, $\frac{B_4}{B_6}=1300\mathrm{}\pm 30$, to be compared with that found for Ag:Dy alloys, ≤340. The linewidth yields an exchange-coupling parameter $J_{\mathrm{fs}}=0.14\mathrm{}\pm 0.05$ eV, slightly larger than for Au:Gd and Au:Er alloys, and slightly smaller than for silver-based alloys.

We report on the polarization dependence of the transverse electroreflectance spectrum of the 4.5-eV (${E_0}^{\prime }$) structure in GaAs. An interpretation using Bottka-Fischer symmetry analysis shows that this transition has $\Delta$ symmetry, in contrast to the corresponding transition in Ge.

High-resolution $L_{\mathrm{I}\mathrm{I}\mathrm{I},\mathrm{I}\mathrm{I}}$ absorption spectra are presented for well-characterized films of amorphous and crystalline silicon. The crystalline spectrum shows features which are related to the detailed conduction-band structure of silicon. These features are not seen for the amorphous material presumably because of the lack of long-range order. The amorphous spectrum rises less steeply than the crystalline and has a broad peak near threshold.

We propose a phenomenological theory for the rotations of the $B{\mathrm{O}}_6$ octahedra in $\mathrm{AB}{\mathrm{O}}_3$ perovskites at structural transitions. The EPR linewidth behaves as ${\epsilon }^{-\nu (1\mathrm{}-2\eta )}$ and the ultrasonic attenuation as ${\omega }^2{\epsilon }^{-\nu (2\mathrm{}-\eta )}$ close to $T_c$. Further away a crossover to different power laws is predicted. We find an anomaly in the sound velocity.

The linewidth broadening of the paramagnetic resonance of the ${\mathrm{Fe}}^{3+}-V_{\mathrm{O}}$ center in SrTi${\mathrm{O}}_3$ near $T_c$ has been measured accurately and analyzed for $T\to {T_c}^{+}$. It is found that the order-parameter susceptibility $\chi (\overrightarrow{\mathrm{q}},T)$ is two-dimensionally anisotropic with an anisotropy parameter $\Delta =\frac{1}{60}$. The critical exponent of the correlation length $\xi$ is found to be $\nu =0.63\mathrm{}\pm 0.07$. The EPR linewidth is cusp shaped for $T\to {T_c}^{+}$ and finite at $T=T_c$.

An exact solution is obtained for some "three-dimensional" Ising models with a four-spin interaction. The spontaneous magnetization is vanishing for all temperatures. The temperature derivative of the susceptibility shows a divergence of the form ${(T_c-T)}^{\frac{-7\mathrm{}}{8}}$ below the critical point. The specific heat shows a logarithmic singularity. Several other related models are introduced with new types of singularities.

The weak $\beta$-delayed proton emitter ${}_{}{}^{23}{}_{}{}^{}\mathrm{Al}$, with a half-life of 470 ± 30 msec, was produced by the reaction ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}\mathrm{}(p,2n)\mathrm{}{}_{}{}^{23}{}_{}{}^{}\mathrm{Al}$. We observed delayed protons with a center-of-mass energy of 870 ± 30 keV and a maximum production cross section $\approx 220$ nb.

We have measured the differential cross sections for the elastic scattering of 10.83-MeV photons by U, Th, and Bi targets and for inelastic scattering to the first excited states of the residual nuclei over a range of scattering angles. The inelastic scattering is found to be significantly weaker than predicted by currently accepted models of the giant dipole resonance.

Cross sections for the reaction $\mathrm{ep}\to \mathrm{ep}{X}^0$, measured by detecting both the scattered electron and the proton, are given for missing masses $m_x$ between 0 and $1 \frac{\mathrm{GeV}}{c^2}$. Enhancements are observed at $m_x=0\mathrm{}$ and in the region of the $\rho$ meson at $q^2=0.1\mathrm{} \mathrm{and} 0.5 {\left(\frac{\mathrm{GeV}}{c}\right)}^2$. The electroproduction of all states with $m_x$ between 0.7 and $0.83 \frac{\mathrm{GeV}}{c^2}$ varies like $e^{-7.5t}$ for $q^2=0.1\mathrm{} {\left(\frac{\mathrm{GeV}}{c}\right)}^2$, similar to missing-mass photoproduction, but for $q^2=0.5\mathrm{} {\left(\frac{\mathrm{GeV}}{c}\right)}^2$ it varies like $e^{-3.5t}$. In this mass region the resolution tail of the large bremsstrahlung peak at $m_x=0\mathrm{}$ is small.

In a scintillation-counter experiment, we have observed two narrow, neutral mesons in addition to the well-established ${\eta }^{\prime } \mathrm{}\left(958\right)\mathrm{}$ in the reaction ${\pi }^{-}p\to M^{0}n \mathrm{at} 2.4 \frac{\mathrm{GeV}}{c}$. We observe a mass of 940.5 ± 1.7 MeV, $\Gamma <10.4\mathrm{}$ MeV for the $M^0\mathrm{}\left(940\right)\mathrm{}$, and a mass of 962.9 ± 1.7 MeV, $\Gamma <5.9\mathrm{}$ MeV for the ${\delta }^0$.

A search has been made for the rare decay mode $K^{+}\to {\pi }^{+}\gamma \gamma$ using a heavy-liquid bubble chamber. No events were found. A test was made of the Fujii model which uses an off-mass-shell extrapolation of the $K_{\pi 2}$ amplitude to make predictions for this decay. The experimental upper limit on the branching ratio is reported to be 2.2 × ${10}^{-5\mathrm{}}$, and this result is consistent with the Fujii model. This result is inconsistent with the branching ratio predicted by the Fujii model.

We have observed anomalous transparency in bound-free transitions of ${\mathrm{Cl}}_2$ in pure ${\mathrm{Cl}}_2$ and in ${\mathrm{Cl}}_2$-He and ${\mathrm{Cl}}_2$-Ar mixtures. From the dependence of transmitted laser energy on pressure, we have estimated the following collision diameters for ${\mathrm{Cl}}_2$-${\mathrm{Cl}}_2$, ${\mathrm{Cl}}_2$-Ar, and ${\mathrm{Cl}}_2$-He collisions, respectively: 4.9, 4.4, and 1.5 Å.

The excitation spectrum of ${\mathrm{N}}^{+}$ has been observed by examining the energy lost by a 50- keV ${\mathrm{N}}^{+}$ beam passing through a He target. The spectrum exhibits dramatic features with large cross sections. Determination of the approximate ratio of metastable to ground-state ions in the primary ion beam has permitted measurement of excitation cross sections from both ground-state and metastable ${\mathrm{N}}^{+}$ ions colliding with He target atoms.

It is shown that the Fredholm determinant for the Lippmann-Schwinger equation may be computed for complex energies using only $L^2$ basis functions. Analytic continuation to the real axis in the $E+i\epsilon$ limit gives elastic scattering phase shifts over a continuous range of energies, showing that it is not necessary to explicitly enforce asymptotic boundary conditions for numerical scattering computations, and suggesting that elastic electron-atom or -ion scattering information may be obtained using standard bound-state configuration-interaction methods.