This Letter investigates the phonon scattering in Si${\mathrm{O}}_2$ glass at frequencies above 100 GHz by phonon spectroscopy with superconducting tunnel junctions. By analyzing the frequencies of the scattered phonons with two independent techniques, evidence is obtained for strong inelastic phonon scattering in glass. Furthermore, the phonon mean free path is determined as a function of the phonon frequency.

New experimental results for second-sound damping near the superfluid transition in ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ are reported. They are a factor of about 5 smaller than previous data, but in good agreement with recent theoretical estimates. These results eliminate a major discrepancy between experiment and renormalization-group-theory predictions for the dynamics of continuous phase transitions.

An ac technique has been used to measure the heat capacity of 8OCB at 1 atm along several high-pressure isobars. The $C_p$ data near the essentially second-order nematic-smectic-$A$ (N-$\mathrm{Sm}A$) transition are inconsistent with the logarithmic singularity expected from the $d=3\mathrm{}$, $n=2\mathrm{}$ model of de Gennes but agree with a power-law divergence with $\alpha ={\alpha }^{\prime }$ in the range 0.2-0.3. This behavior and an unexpected exponential decrease in the magnitude of the critical N-$\mathrm{Sm}A$ heat capacity with increasing pressure are also confirmed in octylcyanobiphenyl (8CB).

A technique is described which graphically displays the anisotropic propagation of non-equilibrium phonons in crystals at low temperatures. Ballistic phonons emanating from a localized heat pulse are channeled preferentially along various crystal directions due to elastic anisotropies. A spatial map of phonon intensities in Ge is collected by continuous scanning over the propagation directions. The data have precipitated a new approach to analyzing the theory of phonon focusing in solids.

Three new Raman lines appearing below the antiferromagnetic ordering temperature of V${\mathrm{I}}_2$ are attributed to zone-boundary-phonon Raman scattering induced by the elastic ("Bragg") magnetic scattering from the spin superstructure. The spin-dependent electron-phonon coupling is explained in terms of a modulation of the exchange interactions by selected zone-boundary phonons.

It is shown that the experimentally observed band narrowing, the large quasiparticle damping, the small exchange splitting, and the existence of satellites can be reproduced semiquantitatively with use of the low-density approximation to describe correlations between Ni $3d$ electrons. The exchange splitting of $t_{2g}$ states (~0.37 eV) is found to be considerably larger than that between $e_g$ states (~0.21 eV). A new satellite is predicted about 2 eV below the main "6-eV" satellite.

The quantum spin-½ Heisenberg antiferromagnet in one dimension with randomly distributed coupling constants is solved approximately. Ground-state energies and low-temperature properties are obtained for several distributions of coupling constants (including both singular and nonsingular distributions). Power-law temperature dependence in specific heat and in susceptibility are found for all distributions studied.

Measurements of the surface composition of a Cu-Ni alloy using Auger electrons with different average escape depths reveal sputter-induced subsurface compositional changes at elevated temperatures which are larger than those produced directly at the surface by preferential sputtering. The compositional gradients which are produced extend to significantly greater depths than have been considered previously.

The magnetic excitations of the incommensurate spin-density wave in pure chromium have been ivestigated with use of inelastic neutron scattering. We have observed the spin wave modes originating from the incommensurate magnetic Bragg reflections. The polarizations of these modes are found to be highly anisotropic. We have also observed a new magnetic excitation centered at a commensurate wave vector. This new excitation is interpreted as a feature specific to a transverse incommensurate spin-density wave.

The temperature dependence of the saturation magnetization of an epitaxial ${\mathrm{Gd}}_{2.3}$ ${\mathrm{Bi}}_{0.7}$-${\mathrm{Fe}}_{4.5}$ ${\mathrm{Ga}}_{0.5}$ ${\mathrm{O}}_{12}$ garnet film irradiated with 180-MeV Xe ions of different doses has been investigated experimentally and analyzed theoretically in terms of molecular-field theory. The magnetic ordering inside the nuclear tracks turns out to be destroyed as a result of the large degree of disorder. The effective nuclear track diameter is estimated to be 15 nm. The molecular-field coefficients deduced from the magnetization curves depend on dose.

This Letter represents a theory of transport in random metal alloys which focuses on certain model-independent features of the electron-phonon dynamics which have been previously neglected. It is found that the adiabatic phonon approximation breaks down in the high-resistivity regime producing an anomalous negative temperature coefficient of resistivity. Model numerical calculations suggest that this mechanism could be the source of the Mooij correlation between the resistivity and its temperature coefficient.

This Letter investigates the conditions for Bose-Einstein condensation of an ideal relativistic Bose gas in different spatial dimensions. It is shown that the thermodynamical properties of the critical particle density are qualitatively different for massive and massless relativistic Bose particles.

It is discovered that the 1-eV positrons formed on an MgO-coated moderator with use of positrons from a ${}_{}{}^{58}{}_{}{}^{}\mathrm{Co}$ source are polarized with degree of polarization $P={0.22}_{-0.02\mathrm{}}^{+0.04\mathrm{}}$. Improved design could increase $P$ to 0.40 with a flux of ${10}^5$-${10}^6$/sec. Applications of this discovery are discussed.

Renormalization-Group methods are used to calculate the critical distribution functions for large groups of ordering coordinates in two- and three-dimensional systems undergoing structural phase transitions. In two dimensions the distribution function shows clear evidence of well-defined clusters of precursor order, and cluster walls: The asymptotic collective behavior is always that of an order-disorder rather than a displacive system. In three dimensions the order-disorder component of the asympototic behavior is markedly weaker.

A Van de Graaff accelerator facility has been used as a supersensitive mass spectrograph in a search for free $+\frac{1}{3}\mathrm{}\left|e\right|\mathrm{}$ and $+\frac{2}{3}\mathrm{}\left|e\right|\mathrm{}$ charged ions in helium gas. No such ions were found at a level of sensitivity better than 1 part in 3.9× ${10}^{14}$ He atoms. The mass ranges spanned were 0.13 to 7.5 amu for $+\frac{1}{3}\mathrm{}\left|e\right|\mathrm{}$ ions and 0.27 to 15.0 amu for $+\frac{2}{3}\mathrm{}\left|e\right|\mathrm{}$ ions.

This Letter proposes, on the basis of the Massachusetts Institute of Technology bag model of hadrons, that extended, massive, multiquark states possessing great strangeness may be metastable. Such novel states of matter would have strangeness to baryon-number ratio $\frac{\mathrm{}\left|S\right|\mathrm{}}{A}\simeq 2$ with $A\gtrsim 10$ and estimated lifetime ≳ ${10}^{-4\mathrm{}}$ sec.

The target dependence of jet production at large transverse momentum observed in $\pi$-Al collisions can be explained in terms of contamination of double-quark jets. Qualitative explanations are given for the difference between pion- and proton-induced jet production.

A particle x-ray coincidence experiment for the compound nuclear reaction ${}_{}{}^{112}{}_{}{}^{}\mathrm{Sn}$($p$,$p^{\prime }$) at 12 and 10 MeV proton energy is presented. A mean nuclear lifetime of 3.4×${10}^{-17\mathrm{}}$ s for ${}_{}{}^{113}{}_{}{}^{}\mathrm{Sb}$ at 15 MeV excitation, and of 4.0×${10}^{-17\mathrm{}}$ s at 13 MeV is deduced.

The measured correlation of charged-particle energies and angles with $\gamma$-ray multiplicities indicate that the average angular momentum transferred in the capture of ${}_{}{}^4{}_{}{}^{}\mathrm{He}$, ${}_{}{}^8{}_{}{}^{}\mathrm{Be}$, and ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ from 153-MeV ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ projectiles by a ${}_{}{}^{154}{}_{}{}^{}\mathrm{Sm}$ target increases linearly with captured mass. These incomplete-fusion processes are shown to originate from undamped peripheral collisions.

This Letter discusses inner-shell excitation in collisions of very heavy ions ($Z_1+Z_2\gtrsim 140$) in the framework of the quasimolecular model. The importance of multistep excitations and of coupling between continuum states is demonstrated. The $1s\sigma$ vacancy probabilities resulting from coupled-channels calculations exceed perturbation theory by a factor 3-5, thus giving good agreement with recent experimental results.