The first physical-property measurements on laser-quenched amorphous Si are reported. The form of the vibrational spectrum and degree of structural order have been obtained by depolarized-Raman-scattering measurements. A thin layer prepared by 700-psec pulses of 3567-Å radiation is found to have a bond-angle variation equal to, but no greater than, that achieved in vapor-deposited pure amorphous Si. The results suggest a maximum allowed order that may be achieved in amorphous Si.

Texture transitions in superfluid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-$A$ are produced by a moving bellows system controlling mass flow. These texture changes are caused by the competition of magnetic, flow, and gradient energies. We have located the boundary of a region of stability with ${\overrightarrow{\mathrm{v}}}_s\parallel \hat{l}\parallel \hat{H}$. This boundary may be related to theoretical predictions of a transition to helical textures, but there is substantial disagreement with the theory over the maximum magnitude of the superfluid velocity in what we interpret as uniform textures.

Measurements of electron transmission spectra and work function $\phi$ of a Ni(111) surface held at $T=5.5\mathrm{}$ K during exposure to ${\mathrm{O}}_2$ provide direct evidence for a precursor adsorption preceding dissociative chemisorption. The form of the electron transmission spectra indicates that the precursor adsorption involves oxygen molecules. Subsequent warming of the oxygen-covered surface leads to the chemisorption state. An analysis of the kinetics of the increase in $\phi$ that accompanies this transition gives an activation energy of ∼ 13 meV for the reaction.

The low-frequency conductivity $\sigma \left(\omega \right)$ of an exactly solvable model of an incommensurate potential is calculated for several classes of commensuration parameter and compared with the random case. The conductivity is related to the degree to which the eigenstates of the model occur in resonating multiplets. It is found that $\sigma \left(\omega \right)\sim {\omega }^x$, where $x=2\mathrm{}$ for the random case, $x=\infty$ for generic commensuration, and $-1<x<\mathrm{}\infty$ for special commensurations. There are fewer resonances for large $x$, with no resonance at $x=\infty$.

First-principles total-energy calculations have been performed for NbH in the $\beta$- and $\gamma$- phase structures. Lattice constants, bulk moduli, and heats of formation as well as the frequencies and second harmonics of the optical vibrations of hydrogen and deuterium in the lattice have been calculated and found to be in excellent agreement with experiment. Our calculated electronic densities of states resolve the discrepancy between previous band calculations and photoemission experiments.

Direct measurements of fluctuations associated with flux flow in superconductors are made with a superconducting quantum interference device. This method avoids the complicated problems concerned with voltage probe locations in earlier work, and allows an unambiguous determination of some characteristic noise power spectra in different current regimes. Models of fluxoid motion are proposed to account for the experimental results.

We discuss properties of bound magnetic polarons in an antiferromagnetic semiconductor placed in an external magnetic field. When the strength of the exchange coupling between the electron spin and local moments is increased, there can be an abrupt transition between a large and a small bound magnetic polaron. Associated with the bound state is a large ferromagnetic moment; our theory provides a quantitative account of magnetization data on EuTe.

Doping superlattices, i.e., multilayer structures consisting of ultrathin ($50 \AA <~d<~400 \AA$) $n$-type, intrinsic, and $p$-type layers of $a$-Si: H (nipi structures), have been produced. Up to a tenfold increase in their infrared photoconductivity after band-gap illumination compared to unstructured $a$-Si: H is observed. The results are well described by a simple model for the carrier recombination kinetics that takes into account the spatial separation of electrons and holes due to the modulation of the band energies.

We have synthesized amorphous-semiconductor superlattices consisting of alternating layers of $n$-type and $p$-type doped, hydrogenated, amorphous silicon. These new amorphous semiconductor structures exhibit a long-lived ($\tau \sim \mathrm{days}$) excess conductivity after a brief light exposure at room temperature. This effect may be attributed to spatial separation of the photocarriers by the $\mathrm{pn}$ junction fields or, alternatively, to defect centers having a barrier against retrapping of photoexcited carriers.

Inelastic scattering of ${}_{}{}^{241}{}_{}{}^{}\mathrm{Am}$ 59.57-keV $\gamma$ rays from Cu and Fe was measured in coincidence with the $K$-fluorescence x rays. The spectrum due to the scattering by the $K$-shell electrons shows the coexistence of a Compton-type and a Raman-type scattering. Double-photon Thomson-type scattering is also identified, which is weaker than the usual Compton scattering by a factor of about 4 × ${10}^{-3\mathrm{}}$.

The size distribution $n_i\mathrm{}\left(t\right)\mathrm{}$ for systems with Smoluchowski aggregation kinetics is shown to have the dynamic scaling form $n_i\mathrm{}\left(t\right)\mathrm{}\sim t^{-\theta }g\left(\frac{1}{t^z}\right)$, with $\theta =2\mathrm{}$ and $z=1\mathrm{}$. This gives a light-scattering intensity $〈I〉\sim t^z$, and an effective hydrodynamic cluster radius $〈R〉\sim t^{\frac{z}{D}}$, where $D$ is the cluster fractal dimension. We find that human immunoglobulin (IgG) monomers exhibit Smoluchowski aggregation kinetics with $z=1\mathrm{}$, and $D=2.56\mathrm{}\pm 0.3$, upon heating to 47-62°C.

The nonspectator contributions to the $B$-meson decays are calculated with use of the measured ratio $\frac{{\tau }_{D^{+}}}{{\tau }_{D^0}}$ and the assumption $\frac{f_B^2}{f_D^2}=\frac{m_D}{m_B}$. We find $\frac{{\tau }_{B^{+}}}{{\tau }_{B^0}}=1.4\mathrm{} \mathrm{to} 1.8$. From the measured values of $B$-meson lifetime, the semileptonic branching ratio, the ratio $\frac{\Gamma (b\to \mathrm{ue}\nu )}{\Gamma (b\to \mathrm{ce}\nu )}$, and the $\epsilon$ parameter, the constraints on Kobayashi-Maskawa angles are evaluated and their implications for $m_t$, $\left|\frac{{\epsilon }^{\prime }}{\epsilon }\right|$, $B^0-{\bar{B}}^0$ mixing, and $K\to \pi \nu \bar{\nu }$ are presented.

Muon and electron production in association with prompt muons has been studied in a 200-GeV/c ${\pi }^{-}$-Be interaction at Fermilab. The prompt dimuon cross section was found to be 3.3 ± 0.6 μb per nucleon. The cross section for muon-electron production was found to be 0.12 ± 0.04 μb. The relative yields of prompt muons at low $x_{\mathrm{F}}$ and moderate $p_t$ from charm and electromagnetic sources are also reported.

A search has been performed for the muon-number-nonconserving decay $\mu \to e^{+}{e}^{+}{e}^{-}$. No candidate event has been found, the result yielding an upper limit for the branching ratio of $B_{\mu 3e}<1.3\mathrm{}\times {10}^{-10\mathrm{}}$ (90% C.L.). From part of the data taken with a trigger that enhanced ${\mu }^{+}\to e^{+}{e}^{+}{e}^{-}{\nu }_e{\bar{\nu }}_{\mu }$ events, eleven such events were observed. They agree in number and spectra with expectations based on standard electroweak theory.

We suggest a scenario according to which the $\mathrm{CP}$-nonconserving interactions responsible for both the generation of matter-antimatter asymmetry in the universe and the microscopic process of $K_L\to 2\pi$ decay have a common origin at high energies. Consistency with the decoupling theorem is discussed. The general characteristics of gauge models that bring out this connection are outlined and a specific SO(10) model is discussed, where $\frac{n_B}{n_{\gamma }}$ and $\epsilon$ are related.

The first calculations of $\bar{p}$-nucleus elastic scattering using the relativistic impulse approximation are presented and compared with the recent 46.8-MeV $\bar{p}$-${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ elastic scattering data. The calculated cross sections agree well with the data. The differences between relativistic and nonrelativistic impulse-approximation calculations using the same input are small.

A new class of low-lying collective modes in nuclei is discussed and experiments to detect these modes are suggested.

The nucleon effective mass was successfully used, as the only free parameter, to adjust the ratio $R\mathrm{}\left(A\right)\mathrm{}$ of structure functions measured in a nucleus of mass number $A$ and in the deuteron, for each $A$ value in the SLAC set of experimental data. The resulting $A$ dependence of the effective mass, being linear in $A^{-\frac{1}{3}}$, is consistent with the behavior expected from nuclear structure considerations. The extrapolated value of the effective mass for nuclear matter agrees with previous estimations.

Relative differential cross sections for charge-transfer scattering have been measured over the collision energy range $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}=45-75\mathrm{}$ eV. With linearly polarized light exciting $\mathrm{Na}\mathrm{}\left(3s\right)\mathrm{}$ to ${\mathrm{Na}}^{*}\mathrm{}\left(3p\right)\mathrm{}$, the dependence of the charge-transfer cross section on the predominant preparation of the $\Sigma$ or $\Pi$ excited states of the ionic quasimolecule ${\mathrm{Na}}_2^{+}$ has been studied. The results are compared to simple model calculations. It is found that the resonant charge exchange is most probable for the predominant preparation of the ${{\mathrm{Na}}_2}^{+}\left(2\mathrm{}{\Sigma }_{\mathrm{g},\mathrm{u}}\right)$ excited states.

Pressure shifts of the standing-wave saturated resonance have been measured in the 9-and 10-μm $P$ and $R$ lasing transitions of C${\mathrm{O}}_2$ with a heterodyne spectroscopic technique. At low pressures (≤100 m Torr) the measured shifts for four different isotopes were all blue, instead of red as predicted by semiclassical theory. Measurements at higher (> 1 Torr) pressures revealed red shifts. Perturber-gas data showed blue shifts for heavier perturber atoms or molecules, red shifts for He and ${\mathrm{H}}_2$.