Using a sensitive SQUID (superconducting quantum interference device) detector and well-shielded dilution refrigerator, we have observed a broad resistance transition below about 1 K on samples of crystalline Bi lightly doped with either tin (0.02-0.23 at.% Sn) or tellurium (0.1 at.% Te). Between 30 mK, which is the lowest temperature available to us, and 60 mK, the resistance of samples containing 0.08-, 0.12-, and 0.16-at.% Sn actually disappears and the transition temperature increases with increasing amounts of Sn.

An impurity spin in one-dimensional spin-½ $X-Y$ and antiferromagnetic Heisenberg models is shown to induce decaying spatial oscillations of magnetization for finite magnetic field. The wavelength of oscillation changes with magnetic field. Since these systems can be described mathematically in terms of a degenerate gas of pseudofermions, their response to impurity perturbation is similar to the response of an electron gas to a localized static charge.

The electronic structure of the Pd(111) surface is calculated using a recently developed mixed-basis pseudopotential method. Fully self-consistent results, including surface states, work function, local densities of states, and electronic charge densities, are presented. The commonly observed adsorbate-induced changes in $d$-band structure in the photoemission spectra are interpreted in terms of the surface states. An $s-p$—like intrinsic surface-state band similar to the one observed on Cu(111) is also predicted.

Raman spectroscopy has been used to study the quasi-one-dimensional charge-density-wave (CDW) compound, Ta${\mathrm{S}}_3$. We determine for the first time both the temperature dependence of the CDW order parameter and the magnitude of the electronic gap $2\Delta \mathrm{}\left(T\right)\mathrm{}$ opened by the CDW at the Fermi surface. The transition to the CDW state appears to be continuous; our value of $2\Delta \mathrm{}\left(0\right)\mathrm{}\simeq 530$ ${\mathrm{cm}}^{-1\mathrm{}}$ is in agreement with both theory and transport measurements.

Electronic density of states, mean-square velocity, and Drude plasma energy are computed from previously reported energy bands for ${\mathrm{Nb}}_3$Ge and ${\mathrm{Nb}}_3$Al. These results, together with the empirical electron-phonon coupling constant deduced from the high superconducting $T_c$, are used to analyze resistivity. Extremely short phonon-limited mean free paths are found. Qualitative and quantitative ideas of saturating resistivity are consistent with our results.

The application of an external magnetic field, during the conversion of $o$-${\mathrm{H}}_2$ into $p$-${\mathrm{H}}_2$, mixes the catalyst paramagnetic impurity wave functions, opening, therefore, new $o-p$ transitions of different symmetry. The dynamical polarization of either the surface electronic spins or the ${\mathrm{H}}_2$ nuclear spins, induced by the ${\mathrm{H}}_2$ rotational system, strongly enhances the catalytic rates.

I construct an entropy function $S\left(t\right)\mathrm{}$ suitable for a system of hard spheres satisfying the (modified) nonlinear Enskog equation, and show that ${\partial }_{t}S\left(t\right)\mathrm{}>~0$. The equality sign holds only when the system has reached absolute equilibrium, in which case $S$ becomes the exact equilibrium entropy of the hard-sphere fluid.

We present two new solutions to the classical Yang-Mills field equations in the presence of a localized external source. These solutions totally screen the charge of the source. They have lower energy than the corresponding Coulomb solution.

We present measurements of $〈y〉$ for deep-inelastic charged-current distributions with incident neutrino and antineutrino energies ranging from 45 to 205 GeV. The neutrino values show little energy dependence, while the antineutrino data indicate a 10% rise over this energy range. Integrated structure functions obtained from our total-cross-section and $〈y〉$ results are also discussed.

It is argued that if multimuon events observed in deep-inelastic muon scattering are manifestations of associated charmed-meson production, then the latter may be responsible for a sizable fraction of observed scaling violations at small values of the scaling variable $x$.

We have studied correlations between two ${\pi }^0\text{'}\mathrm{s}$ produced at the CERN intersecting storage rings, utilizing detectors with large azimuthal acceptance. We find that the previously observed enhancement of two ${\pi }^0\text{'}\mathrm{s}$ produced at azimuthal difference near 180° can be made to vanish when certain kinematic effects are removed. However, we observe aligned configurations above 8 GeV of transverse energy unexplained by such kinematic effects.

The effect of electron-electron Coulomb correlation on orbital-electron capture by the nucleus has been treated by the multiconfigurational Hartree-Fock approach. The theoretical ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$ $\frac{L}{K}$ capture ratio is found to be 0.086, and the ${}_{}{}^{37}{}_{}{}^{}\mathrm{Ar}$ $\frac{M}{L}$ ratio, 0.102. Both ratios are smaller than the independent-particle predictions. Measurements exist for the Ar $\frac{M}{L}$ ratio, and agreement between theory and experiment is excellent.

Excitation functions for the reaction ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}({}_{}{}^{16}{}_{}{}^{}\mathrm{O}, \alpha ){}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$ have been measured from $E_{\mathrm{lab}}\left({}_{}{}^{16}{}_{}{}^{}\mathrm{O}\right)=62\mathrm{} \mathrm{to} 110$ MeV using a counter telescope at ${\theta }_{\mathrm{lab}}=7.5\mathrm{}°$. Selective population of relatively few states at very high excitation energies in ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$ [$E_x\left({}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}\right)>\mathrm{}20\mathrm{}$ MeV] is seen. A possible correspondence is found between these states and the narrow resonances reported in ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$+${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ reactions. In addition, a possible correspondence between averaged yields in ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}({}_{}{}^{16}{}_{}{}^{}\mathrm{O}, \alpha ){}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$ and gross structure seen in several ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$+${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ reaction channels is cited.

Experimental values of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ (${}_{}{}^4{}_{}{}^{}\mathrm{He}$) elastic structure functions up to momentum transfer $q^2=4.0\mathrm{} \mathrm{}\left(2.4\right)\mathrm{}$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$ are presented. They are compared to calculations using three- and four-body wave functions and to asymptotic models.

Double-differential cross sections have been measured for protons, deuterons, tritons, ${}_{}{}^3{}_{}{}^{}\mathrm{He}$, and ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ at laboratory angles of 60°, 90°, and 120° from targets of Al, Ag, and Ta bombarded with 720-MeV $\alpha$ particles. At a given angle the high-energy $\frac{d^2\sigma }{d\Omega \mathrm{dE}}$ spectra are very similar in shape, independent of fragment and target. The nuclear fireball and coalescence models are somewhat less consistent with these data than with high-energy heavy-ion data obtained with the Bevalac.

At 618 MeV bombarding energy, large fission probabilities have been observed for recoil fragments heavier than the target. The probability of sequential fission seems to depend very strongly upon angular momentum as well as upon excitation energy. The out-of-plane widths of the fission fragments together with the above observations imply that a nearly random depolarization of the heavy-fragment angular momentum may occur during the deep-inelastic processes.

We present data for the reaction ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}(p, 2p){}_{}{}^{39}{}_{}{}^{}\mathrm{K}$ at 148.2 MeV. Energy sharing cross sections for the ${\frac{3}{2}}^{+}$ ground state and ${\mathrm{½}}^{+}$ excited state are well described by distorted-wave impulse-approximation calculations. An explicit comparison of the results of the factorization approximation with these experimental results provides considerable support for the usual distorted-wave impulse-approximation treatment.

We report the first observation of positron creation in high-energy ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ + ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ collisions and establish that a dominant fraction of the positron yield is from nonnuclear origins. The excess positron intensity observed over nuclear emission and its projectile energy dependence is consistent with recent predictions for pair-creation processes in the strong time-varying electric fields produced by the combined nuclear charges of the quasimolecular system formed in the collision.

We demonstrate a new technique for the measurement of state-resolved differential cross sections for elastic and inelastic collision processes involving molecules with small level spacing. Lasers are used to label a specific rovibronic level by modulation of its population via optical pumping and to probe the population of neighboring levels by laser-induced fluorescence. First results on ${\mathrm{Na}}_2$ + Ne (He) collisions show that beyond the center-of-mass scattering angle ${\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}=50\mathrm{}°$ nearly all collision events are inelastic.

The NASA Lewis bumpy torus experiment confines and heats a toroidal plasma by the simultaneous application of strong dc magnetic fields and electric fields. Digitally implemented spectral analysis techniques were used to investigate experimentally the frequency-dependent fluctuation-induced transport across the toroidal magnetic field. It was observed that when the electric field pointed radially inward, the fluctuation-induced ion flux was inward and a significant enhancement of the plasma density resulted.