The first measurements on low-temperature-deposited thin-film $a$-I are reported. In situ Raman spectra indicate that $a$-I is a onefold-coordinated semiconductor in contrast to other amorphous solids studied to date. The spectra surprisingly differ from those of molecular systems, indicating appreciable intermolecular coupling. Considerable structural disorder is indicated by a fivefold increase in intramolecular bandwidth relative to $c$-I. Delocalized bonding rather than weak directional covalent interactions is suggested for intermolecular coupling in $a$-I.

Electron-surface collisions have been observed to result in the emission of optical radiation from desorbed atoms and molecules. The first resonance lines of Na and Li from alkali-halide targets, the Balmer lines of hydrogen, and OH molecular radiation are among the optical lines detected. These are the first observations of discrete line and molecular radiation originating from adsorbed particles ejected from the surface due to electron-stimulated desorption.

The metal-insulator transition in granular aluminum has been observed. The resistivity has been varied over six orders of magnitude from metallic to a material where the conduction is via variable-range hopping. As the transition is approached from the metallic side, tunneling measurements have shown a $V^{\frac{1}{2}}$ dependence of the density of states, in agreement with recent theories.

Annealing a foil of a dilute Au: Er alloy at 400 C produced a near-surface layer approximately 0.5 μm thick, with properties different from those of the bulk. These results were obtained using the electron-paramagnetic-resonance (EPR) technique. A theory for the EPR line shape was developed which showed that the $\frac{A}{B}$ ratio of a paramagnetic impurity in a metal can vary when a near-surface layer exists. The theoretical results may explain anomalous $\frac{A}{B}$ ratios observed in EPR experiments on other dilute metal alloys.

Second-harmonic generation at a silver-air interface was enhanced by a factor of ${10}^4$ by surface roughness. The local-field enhancement is believed to be responsible for the effect. An unusually broad luminescence background extending far beyond the anti-Stokes side of the second harmonic was also observed.

The Kosterlitz-Thouless theory applied to two-dimensional superconducting films suggests that vortex unbinding can explain their gradual resistive transitions. An experiment which directly probes the dynamics of unbinding is reported. The results indicate that, if vortex unbinding does occur in our superconducting films, the dynamic theory overestimates the relaxation time by almost two orders of magnitude.

Variations of the rotational energy distributions of NO molecules scattered at a Pt(111) surface have been determined by means of laser-induced fluorescence. Scattering of a rotationally cold (32 K) supersonic molecular beam at a NO-covered surface results in full rotational accommodation due to trapping/desorption. No Boltzmann distribution of the rotational energies is observed if the molecules are directly (specularly) scattered at a graphitic overlayer.

Damage annealing of a silicon wafer covered by a Ti layer has been obtained by irradiation with a ruby-laser 20-ns pulse of 1 J/${\mathrm{cm}}^2$ energy density. The thickness of the metal film was chosen so as to ensure complete absorption of the light in order to avoid the formation of a photoexcited electron-hole plasma in Si. The results show a good annealing of the Si damage and a titanium diffusion coefficient consistent with an epitaxial growth from the melt.

Starting from a genuine discrete version of the Feynman path-integral representation for the partition function, calculations have been made of the energy, specific heat, and the static density-density correlation functions for a one-dimensional lattice model at nonzero temperatures. A Monte Carlo technique has been used to calculate the temperature-dependent properties. The results are compared with exact calculations for short chains, the Hartree-Fock approximation, and a classical model.

Upper limits to astronomical photon backgrounds are used to derive constraints on the radiative lifetime of neutrinos. With the assumption that the radiative decay dominates the decay routes available, comparisons with predicted fluxes exclude radiative lifetimes between ${10}^{13}$ and ${10}^{22}$-${10}^{23}$ sec for neutrinos which decay to lighter neutrinos and 5-50-eV photons. For $m_{{\nu }_L}\ll m_{{\nu }_H}$, this photon-energy range corresponds to a parent-neutrino-mass range of 10-100 eV/${\mathit{c}}^2$.

An enhancement has been observed in the inclusive cross section for direct single electrons produced in $e^{+}{e}^{-}$ annihilations at the $\Upsilon \mathrm{}\left(4S\right)\mathrm{}$. This is interpreted as evidence for a new weakly decaying particle, the $B$ meson. A branching ratio for $B\to \mathrm{Xe}\nu$ of [13±3 (±3)]% is inferred, where the first set of errors is statistical and the estimated systematic error is enclosed in parentheses.

An enhancement in the inclusive cross section for single muons produced in $e^{+}{e}^{-}$ annihilation at the $\Upsilon \mathrm{}\left(4S\right)\mathrm{}$ is observed, confirming the interpretation that a new bare flavor ($B$ mesons) is produced at the $\Upsilon \mathrm{}\left(4S\right)\mathrm{}$. A branching ratio for $B\to X\mu \nu$ of (9.4±3.6)% is obtained. The two-muon decay, $B\to X{\mu }^{+}{\mu }^{-}$ is not observed, providing a 90%-confidence-level upper limit for the branching ratio for that decay of 1.7%. Combining this with our previously reported limit of 5% for $B\to X{e}^{+}{e}^{-}$, we obtain 1.3% as an upper limit for $B\to X{l}^{+}{l}^{-}$.

With use of the LENA detector at the DORIS $e^{+}{e}^{-}$ storage ring, the hadronic cross section and the $\mu$-pair decay branching ratio of the $\Upsilon \mathrm{}\left(9.46\right)\mathrm{}$ resonance have been measured. ${\Gamma }_{\mathrm{ee}}=1.23\mathrm{}\pm 0.10 (\pm 0.14)$ keV, $B_{\mu \mu }=[3.5\mathrm{}\pm 1.4 (\pm 0.4\left)\right]$%, and ${\Gamma }_{\mathrm{tot}}={35}_{-10\mathrm{}}^{+25\mathrm{}} \left(\{+9\mathrm{}\}\{-7\mathrm{}\}\right)$ keV have been obtained. The first set of errors gives the statistical uncertainty. The numbers in parentheses represent systematic errors arising from the uncertainty in the total hadronic cross section.

The measured $d(\gamma ,p)X$ cross section shows a rapid variation around a photon energy $k=390\mathrm{}$ MeV, not explained up to now by pion or nucleon rescattering processes. It is suggested that this and other related results could be explained by the existence of a dibaryonic resonance at a mass of 2.23 ${\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c}}^2$.

It is shown (by means of a perturbation series) that for a class of potentials $V\left(x\right)\mathrm{}$ the stationary distribution of the solution $x\left(t\right)\mathrm{}$ of the quantum Langevin equation approaches in the weak-coupling limit ($f\to 0$) the quantum mechanical canonical distribution of the displacement of the oscillator, subject to the potential $V\left(x\right)\mathrm{}$, if and only if $E\left(t\right)\mathrm{}$ is the operator version of the purely random Gaussian process so that, in particular, higher symmetrized averages ${〈E\left(t_1\right)\cdots E\left(t_n\right)〉}_s$ are expressible in terms of pair correlations, in the usual way.

A study has been made of the breakup of 70-MeV ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$ into the $\alpha +t$ channel. For reactions on a ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ target the ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$ breakup proceeds sequentially through its 4.63-MeV, ${\frac{7}{2}}^{-}$ state. For reactions on a ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ target, there is evidence both for sequential breakup and for an additional breakup process which does not proceed through an excited state of ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$. This latter process is attributed to direct projectile breakup in the nuclear field of the target.

Differential cross sections and vector analyzing powers for the deuteron elastic and inelastic scattering from ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$ and ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ have been measured at 56 MeV. The coupled-channels analysis has been performed to obtain the simultaneous fits to the elastic- and inelastic-scattering data. The dependence of the coupled-channels calculations on the shape of nuclei has been investigated in comparison with the proton inelastic scattering.

The theory is presented for one-photon free-free absorption by electrons scattering from high-$Z$ atoms. The absorption cross section provides sufficient information to resolve the unpolarized-electron total cross section, ${\left|f\right(\theta \left)\right|}^2+{\left|g\right(\theta \left)\right|}^2$, into its individual components for spin-nonflip, ${\left|f\right(\theta \left)\right|}^2$, and spin-flip, ${\left|g\right(\theta \left)\right|}^2$, scattering. The observation of a spin-polarization effect for a spin-independent process (free-free absorption) is analogous to the Fano effect for bound-free absorption.

Photoelectron studies of molecular autoionization resolved into position within the resonance profile, photoelectron ejection angle, and final vibrational state are reported. By using the first members of prominent window and absorption series converging to ${\mathrm{N}}_2^{+}$ $B{}_{}{}^2{}_{}{}^{}{\Sigma }_{\mathrm{u}}_{}^{+}{}_{}{}^{}$ as an example, striking variations of vibrational branching ratios and photoelectron asymmetry parameters within autoionizing profiles are demonstrated. Such triply differential data represent a very detailed characterization of the rovibronic interactions governing molecular autoionization.

A nonneutral ${}_{}{}^7{}_{}{}^{}\mathrm{Li}_{}^{+}{}_{}{}^{}$-ion plasma is described in which ion Langmuir waves are observed for the first time. The properties of these waves near the Brillouin density limit are investigated.