The low-temperature tunneling levels observed in glasses are discussed in terms of the free-volume model. As the system falls out of thermodynamic equilibrium near its glass transition temperature $T_g$, liquid clusters are frozen in. This Letter proposes that voids are formed within the liquid clusters as they in turn freeze at lower temperatures. Approximately ${10}^{-4\mathrm{}}$ such centers form per atom, 1% of which contribute to the heat capacity below 1 K.

Magnetic-susceptibility, electrical-resistivity, and specific-heat measurements on ${\mathrm{Gd}}_{70}$${\mathrm{Y}}_{30}$ single crystals show Curie-Weiss behavior down to a $T_{\mathrm{C}}$ of 218.8 K along both $c$ and $a$ axes. Below 218.8 K the $a$-axis sample shows a second (hence the term "double") Curie-Weiss behavior down to 205.5 K while the $c$-axis sample exhibits a constant magnetic moment. A model is proposed which places the Gd moments on a cone about the $c$ axis at 218.8 K with the random basal-plane component ordering subsequently at 205.5 K.

Angle-resolved photoemission studies of H on the Nb(110) surface show H-related structures with photon-energy-dependent binding energies in normal emission. The development of these features with ${\mathrm{H}}_2$ exposure is pressure and energy dependent. These properties, together with a reversible temperature-dependent amplitude, are attributed to an initial adsorption regime followed by absorption of hydrogen into the near-surface substrate layers of Nb.

High-resolution low-energy electron-diffraction measurements of the (00) beam from Cu(001) are reported. Fine structure near the (11) beam threshold is explained by an interference between the directly reflected wave and a wave internally reflected at the surface potential barrier. With use of this interpretation, the observed lineshapes have been fitted by adjusting two parameters describing the shape of the potential. It is concluded that the long-range potential saturates to a value about one-half the crystal inner potential.

A new ac bridge technique allows detailed photoelectric studies on very small particles suspended in gases. The photoelectric yield $Y$ near threshold $\Phi$ still follows the Fowler-Nordheim law $Y=c{(h\nu -\Phi )}^2$; yet $c$ is generally much larger compared to surfaces of extended solids. For Ag particles of radius 20 Å in an airlike mixture of ${\mathrm{N}}_2$ and ${\mathrm{O}}_2$, $c\simeq 100c_0$, where $c_0$ applies to a macroscopic Ag surface in the same environment.

A major part of the giant Raman scattering by adsorbed molecules on a Ag-island film is shown to be due to the large increase in the electric field at the molecules and to the large electric dipole moment of the molecule-metal-island complex that result from the excitation of the transverse collective electron resonance of the film.

Raman experiments have been performed on single crystals of ${\mathrm{Ag}}_{0.33}$Ti${\mathrm{S}}_2$. New spectral features are observed for $T<\mathrm{}300\mathrm{}$ K. They are attributed to zone folding arising from the formation of a silver superlattice. A theory has been developed which predicts that the intensity of the zone-folded modes should vary with temperature as the square of the longrange-order parameter $\eta$. The experimental results are shown to be in agreement with the ${\eta }^2$ behavior obtained from a two-dimensional lattice-gas model.

High-pressure resistivity measurements on mixed-valence TmSe indicate a new electronic phase transition near 30 kbar at liquid-helium temperature. In the paramagnetic phase, the $\rho -T$ curve shows unexpectedly small pressure dependence, in contrast with the predictions of a simple valence-change model. The onset of the aniferromagnetic ordering triggers a metal-insulator transition for pressures in the range 0-30 kbar. The new high-pressure phase is characterized by a steep decrease of the resistivity below 3.7 K at 32.5 kbar.

Finely layered superconducting Nb/Ge composites have been fabricated with use of a novel deposition scheme and studied as model systems for quasi-two-dimensional superconductivity. Systematic variation of superconducting properties has been observed along with two- to three-dimensional crossover behavior in both the parallel critical fields below $T_c$ and the fluctuation conductivity above $T_c$.

Measurements of the magnetic susceptibility ($\chi$) of quinolinium ${\mathrm{}\left(\mathrm{tetracyanoquinodimethane}\right)\mathrm{}}_2$ are reported over the temperature range $0.45 \mathrm{mK}<T<\mathrm{}40\mathrm{} \mathrm{mK}$ with use of low-field ESR. Down to 7 mK, it is found that $\chi \propto T^{-\alpha }$ with $\alpha =0.81\mathrm{}$ characteristic of a random-exchange Heisenberg antiferromagnetic chain (REHAC). At lower temperatures, the susceptibility peaks, the ESR linewidth greatly increases, and an internal field rapidly builds up. These changes may be due to either hyperfine or dipolar interactions, signalling a crossover from one-dimensional REHAC to a three-dimensional behavior-possibly a dipolar spin-glass.

Cosmological considerations imply that the Weinberg-Salam Higgs boson mass $m_{\mathrm{H}}\gtrsim 9$ GeV. If this bound were violated, the symmetry-breaking phase transition would occur only after extreme supercooling, resulting in too high a ratio of entropy to baryon number.

A vertical-horizontal symmetric ${\left[\mathrm{SO}\mathrm{}\right(10\left)\right]}_V\otimes {\left[\mathrm{SO}\mathrm{}\right(10\left)\right]}_H$ flavor unifying scheme characterized by a natural generation structure is presented. No-go theorems associated with SO(10) embeddings are trivially avoided. All the fermions are assigned to a single irreducible representation, and the intergenerational structure is dictated by the presence of a hypercolor subgroup for which SU(4) is the only tenable candidate. The theory predicts exactly four generations and suggests a color (Pati-Salam) -hypercolor symmetry at medium energies.

The diagrammatic approach to scale breaking, which allows for the fact that the target quark in a hadron is necessarily offshell, is employed to demonstrate that Nachtmann moments do not generally absorb all $\frac{{M_{\mathrm{hadron}}}^2}{Q^2}$ corrections.

Condensation of the operator ${\left({G_{\mu \nu }}^a\right)}^2$ in quantum chromodynamics is shown by constructing the effective potential through the trace anomaly equation. Effects of Wilson loop on the condensation are also studied.

In a study of ${\psi }^{\prime }$ (3684) radiative decays with the Mark II detector at SPEAR, the decay sequence ${\psi }^{\prime }\to \gamma {\eta }_c$ (2980) is observed, with the ${\eta }_c$ (2980) decaying into several completely reconstructed hadronic modes. A mass $M=2980\mathrm{}\pm 8$ ${\mathrm{M}\mathrm{e}\mathrm{V}/\mathit{c}}^2$ and a width $\Gamma <40\mathrm{}$ ${\mathrm{M}\mathrm{e}\mathrm{V}/\mathit{c}}^2$ (90%) confidence level) are obtained, and estimates of some of the decay branching ratios are presented.

An ${\eta }_c$ candidate state has been observed with a mass $M=2978\mathrm{}\pm 9$ MeV and a natural line width $\Gamma <20\mathrm{}$ MeV (90% confidence level) using the Crystal Ball NaI(T1) detector at SPEAR. Radiative transitions to this state are observed from ${\psi }^{\prime }\mathrm{}\left(3684\right)\mathrm{}$ and $\frac{J}{\psi }\mathrm{}\left(3095\right)\mathrm{}$ in the inclusive photon spectra. The branching fraction to this state from the ${\psi }^{\prime }$ is (0.43±0.08±0.18)%, where the errors are statistical and systematic, respectively. In addition, evidence is presented for the decay of this new state into $\eta {\pi }^{+}{\pi }^{-}$ and an upper limit is presented on the decay into ${\pi }^0{K}^{+}{K}^{-}$.

Elastic scattering cross sections for ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$ + ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$ have been measured at 70°, 80°, and 90° (c.m.) in the energy range between 6 and 35 MeV (c.m.). Strongly pronounced, rather regular, gross structure is observed which, at 90°, peaks at 15.5, 19.5, 24, and 28 MeV. The angular distributions suggest a dominance of $l=12, 14, 16, \mathrm{and} 18$, respectively, at these energies. Intermediate structure is observed in the single and mutual $3^{-}$, 6.73-MeV inelastic channels above 20 MeV (c.m.).

A modified heliocentric coordinate system is found for the dynamics of $n+1\mathrm{}$ particles that is barycentric, diagonalizes the kinetic energy, and is symmetric in $n$ of the particles. The $n$ planetary vectors are based on Radau's canonical point between the center of mass and the heliocenter. These coordinates, described by Radau in 1868 and forgotten, are especially valuable for describing centrosymmetric molecular fragments $A{B}_n$, and useful also for the mass polarization in atoms.

Angular distribution and spin polarization of photoelectrons produced by linearly polarized light from the $7{}_{}{}^2{}_{}{}^{}P$ excited states of Cs have been measured. Combination with earlier cross-section measurements of other authors allows a complete determination of the transition matrix elements describing the photoionization process for the $7{}_{}{}^2{}_{}{}^{}P_{\frac{1}{2}}^{}{}_{}{}^{}$ state.

Parameters are introduced to characterize the electron-photon coincidence rate for atoms where spin-orbit interaction is present in the radiating target state. It is shown that two of these parameters (called $\Delta$ and $\epsilon$) obey rigorous selection rules which require that they go to $\frac{\pi }{2}$ at 0° and 180° electron scattering angles in the presence of spin-orbit coupling while their limit in the $\mathrm{LS}$-coupled case is 0. Numerical results are presented.