Both elastic and inelastic electron scattering have been used to characterize and investigate the electronic properties of As${\mathrm{F}}_5$-doped polyparaphenylene. Evidence is presented for the existence of a polaron state slightly above the top of the valence band at low doping levels. An increase in the doping level first leads to the formation of bipolaron states which broaden and finally form a band in the gap in agreement with recent theoretical predictions.

Measurements of the dielectric loss in triglycine sulfate are shown to yield information on the critical temperature dependence of the relaxation time, $\tau \mathrm{}\left(t\right)\mathrm{}$, where $t\equiv \frac{(T-T_c)}{T_c}$. The data indicate a power law ${\tau }^{-1\mathrm{}}\mathrm{}\left(t\right)\mathrm{}\sim t^x$, where $x=0.656+0.025\mathrm{}\simeq \frac{2}{3}$ for $7\times {10}^{-2\mathrm{}}<\Delta T<\mathrm{}1.5\mathrm{}°$C at $T>\mathrm{}{T}_c$. $\tau \mathrm{}\left(t\right)\mathrm{}$ does not diverge at $T_c$, in accordance with theoretical considerations. For $T<\mathrm{}{T}_c$ the data suggest a similar behavior. The role of logarithmic corrections is analyzed, and estimates of the correlation length amplitude ${\xi }_0\simeq 7.86$ Å and the dipole-dipole constant $g\simeq 3.44\times {10}^{-7\mathrm{}}$ ${\mathrm{\AA }}^{-2\mathrm{}}$ are obtained.

Nuclear magnetic resonance measurements are reported for liquid Na-NaBr, Cs-CsCl, and Cs-CsI solutions containing less than 10 mole% metal. Correlation of the resonance shifts, relaxation rates, and de electrical conductivity shows that the electronic mobility is independent of concentration in Na-NaBr, in sharp contrast with the cesium solutions. The results provide an explanation for the apparently anomalous electronic conductivity observed in liquid-sodium-sodium-halide solutions.

By Monte Carlo simulations it is shown that the magnetization $M(T, H)$ of the two-dimensional nearest-neighbor Edwards-Anderson model is proportional to $H^{1-x}$, essentially independent of temperature $T$, for fields $H<\mathrm{}{H_c}^{\mathrm{eq}}\mathrm{}\left(T\right)\mathrm{}$, with ${H_c}^{\mathrm{eq}}\mathrm{}\left(T\right)\mathrm{}\propto T^{\frac{1}{x}}$, the exponent being $x\approx 0.28\pm 0.06$. Irreversible behavior on a time scale $t$ sets in for a field $H_c\mathrm{}\left(t\right)\mathrm{}$ where $\frac{H_c\mathrm{}\left(t\right)\mathrm{}}{T_f\mathrm{}\left(t\right)\mathrm{}}$ nearly follows the De Almeida-Thouless line, although no static nonzero freezing temperature $T_f$ exists. Consequences for the interpretation of related experimental work are discussed.

The critical behavior of the low-field Hall effect in a three-dimensional metal-nonmetal composite near the percolation threshold has been determined for the first time from calculations on a reliable random-resistor-network model. The Hall coefficient $R_e$ is found to diverge as ${|p-p_c|}^{-g}$, where $g=0.29\mathrm{}\pm 0.05$.

The entropy and susceptibility of copper nuclear spins below 1 μK have been measured as a function of temperature both in the paramagnetic and in the antiferromagnetic states. The critical temperature is 63± 10 nK, about 30% of the mean-field estimate. The results are in agreement with calculations based on the spin-wave spectrum of the dipolar and the Ruderman-Kittel interactions in the fee lattice of copper.

Activationless hopping conductivity in a strong electric field is caused by downward jumps of localized carriers along the electric field. Here, the specific mechanism of energy release is considered, which involves an energy-transfer process when energy gained by a downward jump of one electron is radiationlessly transferred to another electron, allowing it to make an upward energy jump. An estimate shows that such processes may provide a noticeable contribution to the total hopping conductivity.

It is shown that Coulomb interactions among quasiparticles can play a determining role in the interband optical transitions of polyvalent metals. Explicit calculations for Mg metal made by configuration-interaction methods greatly improve upon the results of single-particle self-consistent-field calculations.

Recent Mössbauer studies of ${}_{}{}^{57}{}_{}{}^{}\mathrm{Fe}$ in a variety of biological systems, including proteins and membranes, reveal absorption spectra consisting of a narrow "elastic" part and a wide "inelastic part." These results are interpreted here by a model of bounded diffusion in which overdamped harmonically bound particles are in Brownian motion. Excellent fits to experimental data are obtained, which yield values of the mean square displacement $〈x^2〉$ and diffusion coefficient $D$ of the particles.

A new master equation describing the irreversible process of a quantum mechanical Brownian particle is proposed. The master equation is shown to obey the symmetry of detailed balance leading to a quantum analog of the reciprocity relations, and the fluctuation-dissipation theorem is obtained. The method is applied to the damped harmonic oscillator. The relation to previous approaches is discussed.

The embedding of $\mathrm{SU}{\mathrm{}\left(k\right)\mathrm{}}_{\mathrm{HC}}$ composite schemes within flavor-chiral color-asymptotically-free $\mathrm{SU}\mathrm{}\left(N\right)\mathrm{}$ grand unifying theories is examined. It is shown that unless $k=3\mathrm{}$, the associated spectator-composite structure conspires to be real under the residual gauge interactions. The exceptional $n$-preon SU${\mathrm{}\left(3\right)\mathrm{}}_{\mathrm{HC}}$ scheme is capable of supporting a nonexotic quark/lepton spectrum only if $n=4, 5$. The SU(8)-embeddable $n=5\mathrm{}$ case leads to a multigenerational Georgi-Glashow SU(5) picture.

The one-loop Kaluza-Klein anomaly is evaluated explicitly for gauge theories in six, eight, and ten dimensions. The result is well defined and unique, despite the nonrenormalizability of the theory.

General consistency requirements on anomalies in $D=2n$ dimensions are derived with topological techniques. It is shown that for a non-Abelian gauge theory the group-theoretic piece of the anomaly is an overall multiplicative factor for any even $D>~4$.

The authors have formulated supersymmetry at finite temperature, generalizing the recent observations by Van Hove. They find that in a two-dimensional model broken supersymmetry is not restored at high temperature.

This paper reports the result of a search for baryon-number-nonconserving neutron-antineutron transitions in oxygen using a 300-ton water Cherenkov detector located in the Homestake gold mine at a depth of 4200 meters of water equivalent. The 90%-confidence-level upper limit for the neutron partial lifetime for this process is found to be 1.4×${10}^{30}$ yr. According to a recent calculation of neutron-antineutron oscillations in oxygen, this result corresponds to a lower limit on the free-neutron oscillation time of 2×${10}^7$ sec.

Differential electron-scattering cross sections for inelastic excitation of an ion have been measured for the first time. Experiments were carried out in a crossed electron-ion-beam geometry for the $4{}_{}{}^2{}_{}{}^{}S\to 4{}_{}{}^2{}_{}{}^{}P$ transition in ZnII at 75 eV. In addition, differential cross sections were calculated at energies between 15 and 100 eV in a five-state close-coupling approximation in which $4s$, $4p$, $3d^{9}4s^2$, $5s$, and $4d$ states were included. Agreement in shape between theory and experiment at 75 eV is excellent.

A relativistic many-body technique which includes particle-hole excitations of the atomic core is developed to describe the photoexcitation of alkali atoms. The technique is used to study the photoionization of cesium near threshold, where the dipole amplitudes are sensitive to both relativistic and correlation effects. The predicted photoionization amplitudes are free from the gauge ambiguities of Dirac-Fock calculations and are in good agreement with semiempirical calculations and with measurements.

Experimental results are reported for the selection of axial wavelengths of Taylor vortices in a system where the Reynolds number, $R$, is "ramped" spatially from above to below the critical value, $R_c$, for the onset of vortex flow. It is found that a sufficiently slow ramp connecting the supercritical region (containing vortices) to a subcritical region (of purely azimuthal flow) results in the selection of a unique wavelength. A more rapid ramp results in a small $R$-dependent band of allowed wavelengths which grows in width as $R\to R_c$ from above.

Blue shifts of ∼85-60 mÅ have been observed for the first five members of the C vi Lyman series emitted from a laser-produced plasma plume at an electron density near ${10}^{21}$ ${\mathrm{cm}}^{-3\mathrm{}}$. These shifts are much larger than density-dependent effects associated with electron collisions and inhomogeneities in ion-produced electric microfields and opposite to plasma polarization shifts according to the linearized Debye model. A nonlinear Debye-type model is consistent with the measurements.

New low-energy electron-diffraction intensity measurements and dynamical calculations indicate that oxygen in a $c(2\mathrm{}\times 2)$ overlayer resides 0.80±0.025 Å above the top layer of Ni atoms and is displaced 0.30±0.1 Å from the fourfold hollow position along a $〈110〉$ direction. This produces a structure having $C_{2V}$ symmetry with two inequivalent nearest-neighbor Ni-O bond distances of 1.75±0.05 and 2.14±0.08 Å.