Chlorine spin-lattice relaxation has been studied in both powder samples and single crystals of ${\mathrm{K}}_2$Os${\mathrm{Cl}}_6$ in the cubic phase above the structural phase transition at 45 K. The data clearly reflect the condensation of the rotary-lattice-mode phonons as expected. In addition, the powder data suggest the presence of tetragonal-phase dynamic clusters with impurities acting as nucleation centers for their formation.

Using the molecular-dynamics technique we have studied a linear chain with quartic anharmonicity. Particular solutions of the equation of motion, representing clusters (domains), are shown to be relevant for a statistical description of the dynamics. A new excitation branch and the associated central-peak phenomenon are traced back to traveling cluster waves and their lifetime.

We have measured the growth of $F$-band absorption at 532 nm in pure KCl following two-quantum band-gap excitation by a 266-nm pulse. The rise time at $T\approx 25$ K is 11±9 psec. Spectral measurements confirm attribution of the early absorption to $F$ centers. This absorption reflects the generation of new Frenkel defects with the $F$ center created directly in its electronic ground state.

We have observed diffraction patterns in critical dc Josephson tunnel current versus magnetic field applied perpendicular to the junction plane. The patterns can be explained by assuming that the perpendicular field penetrates the edge of each film and channels through the junction parallel to the films. An "edge penetration depth," ${\lambda }_{\perp }$, gives a quantitative description of the patterns and their dependence on the angle of field direction. We have found ${\lambda }_{\perp }\mathrm{}\left(T\right)\mathrm{}\propto {(1-\frac{T}{T_c})}^{-\frac{1}{2}}$.

A limiting value for the supercurrent response of narrow superconductors upon flux passage has been deduced from measurements of the 9.2-GHz impedance of thin cylindrical films. The observed times are in good agreement with the predicted relation ${\tau }_1\simeq \frac{\hslash }{2\Delta \mathrm{}\left(T\right)\mathrm{}}$, where $2\Delta \mathrm{}\left(T\right)\mathrm{}$ is the BCS energy gap for the material.

Negative-muon spin rotation at the oxygen site in paramagnetic MnO has been observed at room temperature. A paramagnetic shift of (1.16 ± 0.21)% was observed, approximately one-third the shift observed for the ${}_{}{}^{17}{}_{}{}^{}\mathrm{O}$ NMR in MnO. The muon-spin relaxation time extrapolated to zero external field was determined to be ${1.5}_{-0.4\mathrm{}}^{+0.8\mathrm{}}$ μsec. Possible mechanisms for explaining these observations are presented.

A model based on noninteracting droplet fluctuations is used to describe the phase diagram for electron-hole liquid condensation in semiconductors. All liquid and gas densities are related to the liquid density at low $T$. Good agreement is obtained by fitting recent detailed measurements of the phase diagram for Ge, and an experimental estimate of droplet surface tension (∼1.0×${10}^{-4\mathrm{}}$ erg/${\mathrm{cm}}^2$) is obtained. Theoretical values of the critical temperature and density for Ge are given. A theoretical phase diagram for Si is presented.

The differential cross section of ${\pi }^{+}p$ elastic scattering has been measured in two high-statistics bubble-chamber exposures at laboratory beam momenta of 3.7 and 7.1 GeV/c. A new feature suggested by these data is a dip in $\frac{d\sigma }{\mathrm{du}}$ at $-u\simeq 3$ Ge${\mathrm{V}}^2$. This dip corresponds well to the third zero of $J_0\left(b\sqrt{-u^{\prime }}\right)$, where $\frac{\hslash c}{b}=1\mathrm{}$ fm. The effective $u$-channel Regge trajectory computed for these two energies has a slope of 0.22 ± 0.26.

Data from $e^{+}{e}^{-}$ annihilation into hadrons at 4.8 GeV center-of-mass energy were used to search for charmed mesons in the mass range 1.5 to 4.0 GeV/${\mathit{c}}^2$. We looked for narrow peaks in the invariant-mass distributions for $K^{\mp }{\pi }^{\pm }$, ${K_s}^0{\pi }^{+}{\pi }^{-}$, ${\pi }^{+}{\pi }^{-}$, $K^{+}{K}^{-}$, $K^{\mp }{\pi }^{\pm }{\pi }^{\pm }$, ${K_s}^0{\pi }^{\pm }$, ${K_s}^0{K}^{\pm }$, and ${\pi }^{+}{\pi }^{-}{\pi }^{\pm }$. We present upper limits for the inclusive production cross section times the branching ratio for charmed mesons having these decay modes.

Electron-${}_{}{}^{116}{}_{}{}^{}\mathrm{Sn}$ scattering spectra were obtained over an excitation energy range of about 100 MeV. The experimental transverse spectrum is in good agreement with the Fermigas model, but not the longitudinal spectrum. The quasielastic contribution was then obtained from the shape of the transverse spectrum. The residual amount interpreted to be the resonance part was divided into many multipoles.

We have measured the $\gamma$-ray branching ratios of the lowest $T=\frac{3}{2}$ levels in ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^{13}{}_{}{}^{}\mathrm{N}$, and the absolute strength of the ${\gamma }_0$ transition in ${}_{}{}^{13}{}_{}{}^{}\mathrm{N}$. The mirror electromagnetic selection rule is obeyed by the $M1\mathrm{}$ (${\gamma }_0$ and ${\gamma }_2$) transitions. However the $E1\mathrm{}$ (${\gamma }_1$) transitions exhibit a surprisingly large charge asymmetry. Charge-dependent differences in the radial wave functions do not account for a similar asymmetry in strong $T=\frac{1}{2}\to T=\frac{1}{2}$ $E1\mathrm{}$ transitions in mass 13.

Particles produced at high energies are channeled into narrow forward cones. This channeling is tight enough so that particles produced in an aligned single crystal have a non-negligible chance of interacting with downstream nuclei. The interaction probability including lattice vibrations is estimated. "Super multiple scattering" in single crystals is considered and shown to make this technique less suitable for charged particles. Applications are suggested including the possibility of charmed-particle-interaction experiments.

Resonance ionization from the ($2s2p$) ${}_{}{}^1{}_{}{}^{}P$ and ($2p^2$) ${}_{}{}^1{}_{}{}^{}D$ levels of helium has been observed in an ($e, 2e$) experiment, in which the kinematics of all electrons in fully determined, at incident energies of 200 and 400 eV and a scattering angle of 10°. The results show that as the angle of emission approaches the direction $-\overrightarrow{\mathrm{Q}}$, where $\overrightarrow{\mathrm{Q}}$ is the momentum transfer to the helium atom, the resonance profile becomes more symmetric and the resonance cross section increases sharply.

We show that $K$-shell photoionization spectra of diatomic molecules can exhibit strong shape resonances near threshold. The molecular field is decisive in this phenomenon. It induces the resonant contraction of high-$l$ components of the ionization channels, and it couples these components with low-$l$ components produced in the atomic cores by $K$-shell photoionization. We demonstrate the effect for ${\mathrm{N}}_2$ by using the multiple-scattering model. Clear evidence for this phenomenon exists for ${\mathrm{N}}_2$, CO, and NO.

"Turbulent" electrostatic shocks with imploding cylindrical wave fronts were produced in a modified double-plasma device. The growth rate of turbulence is found to be less than for planar shocks produced in the same device. This behavior is attributed to the fact that for sufficiently small radii of curvature only cylindrically symmetric ion-acoustic modes will exhibit substantial growth while in the planar case maximum growth can occur for off-axis (three-dimensional) modes.

The nonlinear saturation and evolution of the parametric instability which occurs near the critical density (microwave frequency, ${\omega }_0$, equals plasma frequency, ${\omega }_{\mathrm{pe}}$) is studied experimentally. A strong anomalous heating of electrons is observed after the instability saturates. For high powers, a large fraction of the absorbed energy is given to suprathermal electrons. The results may be explained in terms of quasilinear diffusion of electrons in parametrically induced turbulence.

Repeated creation and annihilation of positive and negative pulses of spatially trapped particles are numerically observed as a result of nonlinear interactions in an extremely unstable macroplasma. Positive and negative pulses are successively created at opposite trapping boundaries and propagate toward each other with nearly constant speeds. Each pair of pulses collides and disappears at the center. New pulses are generated at shorter spacing, but propagate faster so that the time interval is nearly conserved.

A model for anomalous diffusion in the bcc phase of group-$\mathrm{IV}B$ transition metals is proposed, based on the identity of structure of the activated complex for diffusion and the basal plane of the low-temperature metastable $\omega$ phase. An expression for the diffusion coefficient is derived from a phenomenological free energy of formation of an $\omega$ embryo. Excellent agreement is obtained with experimental data for bcc Zr.

Highly resolved satellite peaks due to acoustoelectrically amplified phonons are observed on the wings of double-crystal x-ray diffraction peaks in InSb single crystals. The frequencies of the observed phonon peaks range between 0.9 and 6.3 GHz, depending on carrier concentration. Second- and third-order satellites are also visible in all profiles, showing the generation of second and third harmonics of the fundamental frequencies of the amplified phonons and, possibly, the existence of multiphonon scattering.

The main peaks of the angular distribution of atoms inelastically reflected from a crystal surface are shown to be associated with analytical critical points of the surface phonon dispersion curves, particularly those of Rayleigh and Lucas modes. Because of such a relation, the frequencies and wave vectors of these modes could be measured by analyzing the shift of the peaks under a change of the angle of incidence.