With computer experiments we investigate the behavior of large-amplitude, high-phase-velocity plasma oscillations in an electron-ion plasma. The experiments show that such a wave, when above a given threshold amplitude, produces an instability that results in its anomalous damping. The results are in agreement with theory. This is one mechanism by which large-amplitude electrostatic oscillations generated by an instability (for example, by the two-stream instability) can be dissipated.

A dynamic theory, based on the electron-phonon interaction, of the cubic-to-tetragonal transformation in the $\beta$-tungsten structure is presented. The theory explains why ${\mathrm{Nb}}_3$Sn behaves differently from ${\mathrm{V}}_3$Si and shows that the lattice softening does not influence the superconducting transition.

Measurements of the onset of the resistive transition and the current-voltage characteristics of "one-dimensional" single-crystal tin whiskers have been extended to a sensitivity of ${10}^{-15\mathrm{}}$ V. The thermally activated quantum phase slips proposed by Langer and Ambegaokar have been observed directly and their theory for the voltage, determined by the rate of phase slippage, has been verified together with the modification of the attempt frequency proposed by McCumber and Halperin.

High-frequency localized vibrational modes of impurities in a III-V compound have been observed by Raman scattering. Three lines from the GaP samples closely correspond to some local modes previously reported in infrared studies, and depolarization measurements tend to confirm their proposed assignments. We describe several attractive features of this method for the study of semiconductor impurities.

The first measurement of light scattering from rotations, as contrasted to strains, is reported in solids. Brillouin-scattering cross sections in rutile, previously expected to be equal in intensity, were found to differ by ∼${10}^3$. The difference between the deduced photoelastic coefficients confirms quantitatively the recent prediction of this effect.

It is shown that Raman scattering from polycrystalline piezoelectric solids contains all of the essential features of Raman single-crystal spectra even when the crystal spectrum is quite anisotropic. As an illustration of the Raman powder technique, the ceramic ferroelectric-antiferroelectric system PbTi${\mathrm{O}}_3$-PbZr${\mathrm{O}}_3$ has been investigated and the "soft" $E\left(\mathrm{TO}\right)$ optical phonon modes measured in the tetragonal ferroelectric region.

Certain lattice-dynamical properties of dilute Fe impurities in cubic transition-metal hosts are found from Mössbauer-effect studies to be correlated in a simple and unexpected way with the host properties and the impurity mass. The correlation is consistent with the hypothesis that the effective force constant associated with impurities is proportional to the geometric mean of the force constants for the impurity in bulk and for the host lattice in bulk. This result has applicability to testing of the McMillan theory of superconductivity.

The diffraction of thermal beams of helium and deuterium has been observed from a carbide overlayer on tungsten (110). The diffraction grating derived from the atomic and molecular diffraction agrees with that determined by electron diffraction. Peaks through second order have been resolved and helium peaks are characterized by extremely high intensities and narrow half-widths. Use of atomic diffraction to study species which adsorb in a regular array is suggested.

The experimental magnetoelastic properties of antiferromagnetic Mn${\mathrm{F}}_2$ are found in certain specific instances to be completely inconsistent with the usual small-strain magnetoelastic theory. Rigorous application of finite-deformation magnetoelastic theory including the effect of the rotational component of the shear deformation leads to results which are in excellent agreement with experiment.

Evidence is presented which demonstrates that the larger part of the anomaly above $T_c$ in the $c$-axis electrical resistivity of gadolinium arises not from spin-disorder scattering but rather from the anomalous lattice contraction near $T_c$. The portion of the resistance anomaly attributable to spin-disorder scattering is monotonic in temperature and of the general form specified by the Fisher-Langer model.

The thermal and electrical conductivities of several transition alloys have been measured at low temperatures at high magnetic fields. The Permalloys 70Ni-30Fe and 81Ni-19Fe show a 3% magnon conductivity at 4 K. The temperature dependence of the magnon conductivity for these two alloys implies that the magnons are scattered by the electrons through the $s-d$ exchange.

A thick-target time-of-flight technique has been employed to measure neutron energies for ($p,n$) resonance levels near threshold in medium-weight nuclei. Combining the results with proton energy measurements of these resonances, the following ground state $\mathrm{}(p,n)\mathrm{} Q$ values have been deduced: ${}_{}{}^{41}{}_{}{}^{}\mathrm{K}$, -1203.8±0.5 keV; ${}_{}{}^{45}{}_{}{}^{}\mathrm{Sc}$, -2843.6±4.0 keV; ${}_{}{}^{51}{}_{}{}^{}\mathrm{V}$, -1533.7±1.5 keV; and ${}_{}{}^{57}{}_{}{}^{}\mathrm{Fe}$, -1618.2±2.0 keV.

We have measured the time distribution of the ${\pi }^{+}{e}^{-}\nu$ and ${\pi }^{-}{e}^{+}\nu$ modes from initial $K^0\text{'}\mathrm{s}$ in a spark-chamber experiment performed at the Bevatron. From 1079 events between 0.2 and $7 {K_S}^0$ lifetime, we find $\mathrm{Re}X=-0.069\mathrm{}\pm 0.036$, $\mathrm{Im}X=+{0.108}_{-0.074\mathrm{}}^{+0.092\mathrm{}}$. This result is consistent with $X=0\mathrm{}$ (relative probability = 0.25), but more than 4 standard deviations from the existing world average, +0.14 -$0.13i$.

Measurements have been made on Compton scattering for photon energies between 5 and 17 GeV and $t$ values from -0.06 to -1.1 ${\left(\frac{\mathrm{GeV}}{c}\right)}^2$. The data were obtained by performing a coincidence between the Stanford Linear Accelerator Center 1.6-$\frac{\mathrm{GeV}}{c}$ spectrometer and a Lucite shower counter. The scattering appears diffractive out to high $t$ values, but the cross sections seem not to be in good agreement with the prediction of a strict vector-meson-dominance model.

The production of $\Delta \mathrm{}\left(1236\right)\mathrm{}$ by linearly polarized photons at 2.8 and 4.7 GeV was studied using a hydrogen bubble chamber. At 2.8 GeV the cross sections for $\gamma p\to {\Delta }^{++}{\pi }^{-}(\gamma p\to {\Delta }^0{\pi }^{+},{\Delta }^0\to p{\pi }^{-})$ were found to be 3.7 ± 0.4 μb (0.5 ± 0.2 μb); at 4.7 GeV, 1.0 ± 0.1 μb (0.16 ± 0.09 μb). Measurement of the parity asymmetry, $P_{\sigma }$, for ${\Delta }^{++}$ production with $\mathrm{}\left|t\right|<0.5\mathrm{}$ Ge${\mathrm{V}}^2$ yielded the values -0.27 ± 0.12 and -0.53 ± 0.15 at 2.8 and 4.7 GeV, respectively, whereas pure one-pion exchange would lead to $P_{\sigma }=-1\mathrm{}$.

An enhancement in the $2{\pi }^0$ mass spectrum in the region $M_{\pi \pi }<1\mathrm{}$ GeV has been observed in ${\pi }^{-}+p\to {\pi }^0+{\pi }^0+n$ at 10 $\frac{\mathrm{GeV}}{c}$. This is interpreted as a broad isospin-0, $s$-wave resonance at 600±100 MeV with width 400±100 MeV. Because of limited mass resolution, we cannot rule out several narrower resonances with these quantum numbers.

We study the scale dimensions of current components and Schwinger terms. We state and prove necessary and sufficient conditions for the spatial and temporal components of hadronic currents to have the same dimension. The incompatibility of well-defined $c$-number Schwinger terms with universal dimensionality of current components is demonstrated. Experimental implications are discussed.

We compute the spectral distribution for double light scattering by a pair of optically isotropic molecules in a gas. We obtain a good fit with experimental data in C${\mathrm{H}}_4$ when we use a Lennard-Jones potential to calculate classical relative trajectories of the two particles. Observed depolarized intensities are compared with calculated ones.

Two coupled equations describing the nonlinear interaction of ion sound waves and lowfrequency electromagnetic waves are derived for the case where the two phase velocities are close to each other. These equations form a hyperbolic system, thus describing the formation of discontinuities, and can be relevant to the magnetic energy conversion problem in the physics of solar flares.

The Hastie-Taylor guiding-center stability criterion for magnetic-well equilibria of the "mod-B" type is extended to include the effect of quasirigid external currents such as those of an Astron $E$ layer.