We have measured the carbon $K$ edge in graphite using inelastic-electron-scattering spectroscopy. The extended x-ray absorption fine structure is in good agreement with theory for the first-neighbor atoms at a distance of 1.42 Å. The momentum dependence of the edge structure is in qualitative agreement with a simple band-structure picture. A comparison of the signal counting rates for electron-energy-loss and photoabsorption experiments shows that the energy-loss method is competitive with synchrotron radiation sources up to about 1000 eV.

The observed condensation of DNA in salt solution in the presence of a second polymer of lower molecular weight is treated by straightforward statistical mechanics. We neglect the details of DNA structure and represent it by a simple polymer of large molecular weight interacting via single-contact repulsive forces with a large number of smaller polymers. In this approximation, the derivative of free energy with respect to the size of the large polymer shows a singularity at a critical concentration of smaller polymers.

We calculate in quantum-chromodynamic perturbation theory the spin-spin asymmetries for the fundamental 2→2 scattering processes involving quarks and gluons. Using simple, reasonable assumptions concerning the distribution functions for definite-helicity quarks and gluons in a spinning proton we find that the idea that large-$p_T$ events arise from the hard scattering of quarks and gluons leads to a measurable asymmetry for inclusive hadron production at large $p_T$ from a polarized beam and target.

Nuclear charge, mass, and kinetic energies were measured for fragments from the reactions of ${}_{}{}^{86}{}_{}{}^{}\mathrm{Kr}$+ ${}_{}{}^{124}{}_{}{}^{}\mathrm{Sn}$ at 440- and 720-MeV bombarding energies. From these data it was deduced that the internal excitation energy of the strongly damped products divides proportionally with the mass.

Under suitable conditions, relativistic corrections to the interaction of a photoelectron with its parent ion are enhanced, giving rise to large anisotropic final-state effects which can be observed in the photoelectron angular distribution. The particular example of $5s\to \epsilon p$ photoionization of Xe is considered in detail. It is shown that the angular asymmetry parameter $\beta$ is reduced by a factor of 9 from its nonrelativistic value of 2 near the $5s$ "Cooper minimum," so that the energy dependence of $\beta$ becomes a sensitive test of atomic correlation theories.

The isothermal density dependence of both the shift and width of the Raman $Q$ branch in oxygen gas have been found to exhibit anomalous behavior under near-critical conditions. The observed effects are interpretable in terms of molecular-cluster formation, and it is concluded that the Raman effect is a potentially valuable probe of density fluctuations in the critical region.

We show how the target-thickness dependence of heavy-ion-induced x-ray production cross sections can be used to normalize the measured $K$ REC (radiative electron capture) intensity to the fraction of incident ions with $K$ vacancies. Experimental REC cross sections for Cl ions on Cu targets are in good agreement with the free-electron theory of Bethe and Salpeter if it is assumed that all of the $M$- and $N$-shell electrons in Cu contribute to the REC process.

An extensive study has been made of the large magnetic fields in the plasma near the focus of a high-irradiance Nd-laser beam. The dependence of the magnetic field on many experimental conditions is noted—particularly timing and the presence of a preformed plasma. The data were obtained with a Raman-shifted, three-channel Faraday-rotation diagnostic system.

Flash heating by a laser pulse has been used to desorb loosely bound species from a spot on the tokamak wall. Spectral analysis of the suddenly increased impurity radiation from the plasma in front of the laser-heated spot gives information on the species and the amount of impurity atoms present on the surface at a specific point in time of the tokamak discharge. Loosely bound chromium has been found on the stainless-steel surface.

Evidence is presented from differential thermal analysis to show that mercury is extruded from the linear-chain mercury compounds ${\mathrm{Hg}}_{2.86}$As${\mathrm{F}}_6$ and ${\mathrm{Hg}}_{2.91}$Sb${\mathrm{F}}_6$ when cooled below 200 K. The anisotropic superconductivity observed recently in ${\mathrm{Hg}}_{2.86}$As${\mathrm{F}}_6$ is shown to result from extruded mercury.

We have performed heat-pulse propagation measurements in amorphous Si${\mathrm{O}}_2$ over the temperature range 50 mK to 3.8 K on the submicrosecond time scale (some two to three orders of magnitude faster than previous measurements). No evidence for deviations from the dc heat capacity have been observed at low temperatures. Between 1 and 2 K, we see evidence for "ballistic" phonon propagation, induced by saturation of the scattering centers.

The dependence of the superfluid density ${\rho }_s$ on velocity $v_s$ (with $v_n\simeq 0$) has been measured for the first time by observing the shift with amplitude of the resonant frequency of a superfluid Helmholtz resonator. The results agree within experimental and calibration error with the theoretical prediction of Khalatnikov.

The influence of the presence of cylindrical voids on the linear magnetoresistance of indium wires is studied experimentally. We show that the voids increase the linear magnetoresistance drastically in accordance with a theoretical model.

We present evidence that in carbon-polyvinylchloride composites, consisting of aggregates of carbon spheres (100-400 Å) dispersed in the insulating matrix, the electrical conductivity can be ascribed to a novel mechanism of tunneling with potential-barrier modulation by thermal fluctuations. Theoretical consideration of the tunneling-probability modification by thermal fluctuating electric field across tunnel junctions yields expressions for the temperature and the field dependences of the conductivity in excellent accord with experimental results.

Recent measurements of the temperature-dependent electrical resistivity ${\rho }_T$ of potassium down to 1.1 K have indicated the presence of a possible new term $A{T}^n$, with $2>n>\mathrm{}1\mathrm{}$ and $A\propto {\rho }_0$, the residual resistivity. We have measured ${\rho }_T$ down to ≅ 0.5 K in order to confirm the existence of this term and to examine it more closely. We indeed find $A\propto {\rho }_0$ and $n\simeq 1.5$. We speculate that it arises from the electron-electron interaction modified by a size effect and possibly dislocation scattering.

It is demonstrated that the spin-lattice relaxation rate for thallium nuclei in the glassy semiconductor ${\mathrm{Tl}}_2$Se${\mathrm{As}}_2$${\mathrm{Te}}_3$ between 130 and 300 K is limited by spin diffusion and is a thermally activated (Arrhenius) process. These facts indicate that the dominant relaxation mechanism is provided by thermally activated localized electronic states in the gap whose density can be estimated from the measured spin-lattice relaxation time.

A self-consistent pseudopotential calculation of the diamond-metal interface is used to examine interface states and empirical correlation for the dependence of the Schottkybarrier height and interface index, $S$, on ionicity. The properties of diamond are crucial because of its large gap and zero ionicity. Predictions based on experimental extrapolations give $S\approx 0$. Our calculations give $S=0.4\mathrm{}$ and a barrier height of 2.2 eV; the latter is in good agreement with experiment.

Open-orbit electrons are shown to generate an ultrasonic wave throughout a metal when the conditions for an open-orbit resonance are satisfied.

Results are presented from an experiment conducted at Fermilab to measure the polarization parameter in $p-p$ elastic scattering at momenta between 20 and 200 GeV/c at $\mathrm{}\left|t\right|\mathrm{}$ values between 0.3 and 1.0 GeV/${\mathit{c})}^2$. Recoil protons from the interaction of the circulating Fermilab beam and a hydrogen gas jet were spin analyzed in a carbon polarimeter and significant polarizations were observed. The results are compared with the predictions of exchange models.

We examine tests of quantum chromodynamics in the production of lepton pairs in hadronic collisions. We emphasize the need for detailed experimental studies of the transverse spectra of lepton pairs. As a further test, we calculate the production of real photons at high transverse momentum. $\frac{\gamma }{\pi }$ ratios at the 10% level are predicted for $p_T=4-6\mathrm{}$ GeV, with $(pp\to \gamma X)\simeq (pp\to \pi X)$ at $p_T\simeq 10$ GeV.