We have observed a new excess dc current in the current-voltage characteristics of Sn-Sn oxide-Sn Josephson tunnel junctions with large length-to-penetration-depth ratio. This excess current has a magnetic field dependence similar to the absorption curve commonly observed for magnetic resonances. The magnitude of the excess current increases rapidly for bias voltages greater than $\frac{\Delta }{e}$, indicating that pair-breaking processes are involved.

Bulk Si valence charge densities calculated in a completely parallel manner for a traditional weak pseudopotential, a pseudopotential with a strongly repulsive core, and the full potential are compared. The second and third are in excellent agreement, while the first displays a somewhat modified bond-charge shape.

High-resolution electron energy-loss spectra show unexpected features of electronic excitations in stage-1 Fe${\mathrm{Cl}}_3$-intercalated graphite. A sharp 1-eV plasmon surprisingly exhibits positive quadratic dispersion and damping characteristic of a free three-dimensional electron gas. However, the dispersion coefficient is very large and the intensity falls unusually sharply with increasing momentum, indicating the likelihood of strong band-structure effects. An intense 5.9-eV energy loss is identified with a shifted $\pi$ plasmon in graphite consistent with only weakly perturbed carbon $\pi$ bands.

The plasmon modes of the electron-hole plasma in GaP are investigated by pulsed Raman scattering. The two branches of the coupled plasmon-phonon modes are undamped and are observed over a wide energy range, depending on the excitation density. From this variation it is deduced that the density of electron-hole pairs varies in the range of (1-4) × ${10}^{18}$ ${\mathrm{cm}}^{-3\mathrm{}}$.

Arguments are presented that the $T=0\mathrm{}$ conductance $G$ of a disordered electronic system depends on its length scale $L$ in a universal manner. Asymptotic forms are obtained for the scaling function $\beta \mathrm{}\left(G\right)=\frac{d\ln G}{d\ln L}$, valid for both $G\ll G_c\simeq \frac{e^2}{\hslash }$ and $G\gg G_c$. In three dimensions, $G_c$ is an unstable fixed point. In two dimensions, there is no true metallic behavior; the conductance crosses over smoothly from logarithmic or slower to exponential decrease with $L$.

For transition metals I report the dependence of the acoustic-wave-induced electric field gradient (EFG) on $N\left(0\right)\mathrm{}$, the electronic density of states at the Fermi-energy ${\epsilon }_{\mathrm{F}}$. It is shown that the EFG due to linear volume deformation of the unit cells of the crystal is proportional to $N_s\mathrm{}\left(0\right)\mathrm{}$, the $s$-electron density of states at ${\epsilon }_{\mathrm{F}}$, but does not correlate with $N\left(0\right)\mathrm{}$ which is in general largely due to $d$ electrons. However, the EFG due to longwavelength shear waves correlates linearly with $N_d\mathrm{}\left(0\right)\mathrm{}$, the $d$-electron density of states at ${\epsilon }_{\mathrm{F}}$.

By means of a stroboscopic positive-muon-spin rotation technique, the Knight shift of the local field at positive muons in Na, K, Rb, Cs and Be, Mg, Ca, Sr, Ba and in Cu has been measured to a high precision. The results are discussed in relation to recent theoretical calculations on the local electronic structure of hydrogen in metals.

We extend our previous method of proving the positive-mass conjecture to prove the positive-action conjecture of Hawking for asymptotically Euclidean metric. This result is crucial in proving the path integral convergent in the Euclidean quantum gravity theory.

Extremely sensitive readout of a stable "etalon of length" is achieved with laser frequency-locking techniques. Rotation of the entire electro-optical system maps any cosmic directional anisotropy of space into a corresponding frequency variation. We found a fractional length change $\frac{\Delta l}{l}=(1.5\mathrm{}\pm 2.5)\times {10}^{-15\mathrm{}}$, with the expected $P_2\left(cos\theta \right)$ signature. This null result represents a 4000-fold improvement on the best previous measurement of Jaseja et al.

We have measured total hadronic photoproduction cross sections on carbon, copper, and lead. Tagged-photon energies ranged from 20 to 185 GeV for copper and from 45 to 82 GeV for carbon and lead. The energy and $A$ dependence of shadowing were computed by comparing these results to the hydrogen cross section as measured nearly simultaneously with the same apparatus. We observed somewhat more shadowing than did most experiments at lower photon energies.

An examination of 3.6×${10}^{10}$ ${\mu }^{+}$ decays yields an improved upper limit for the branching ratio $\frac{\Gamma ({\mu }^{+}\to e^{+}\gamma )}{\Gamma ({\mu }^{+}\to e^{+}{\nu }_e{\overline{\nu }}_{\mu })}<1.9\mathrm{}\times {10}^{-10\mathrm{}}$ with 90% confidence.

Projectile residues have been studied in coincidence with fragments resulting from fission of the target residue for reactions induced by 315-MeV ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ ions on a ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ target. A kinematical analysis shows that the forward linear momentum transferred to the target nucleus is significantly smaller than that expected for simple transfer reactions, but larger than that expected for pure projectile fragmentation processes.

The narrow experimental width of the $Z$ distribution at fixed mass asymmetry in heavyion reactions is interpreted in terms of a giant dipole mode whose damping increases with excitation energy. Further theoretical predictions and relevant experiments are discussed.

A nonresonant diffraction-model calculation is found adequate to describe the gross-structure behavior thus far observed in the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ + ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ + ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ inelastic scattering excitation functions.

We find evidence for strong, collision-averaged excitation coherence between $2s$ and $2p_0$ amplitudes in charge transfer by fast protons ($v_i\approx 2-3$ a.u.) undergoing single collisions in He, Ar, and ${\mathrm{O}}_2$. Quantum beat difference signals in $\mathrm{Ly}\alpha$ (Eck beats) induced by reversible electric fields have amplitudes very similar to those seen earlier in C targets, supporting a "last-layer" (gas-layer?) hypothesis.

We have measured the mobility of positive ions in ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ vapor for temperatures between 1.3 and 2.0 K and for saturation ratios between 0.1 and 1.0. We present a model which relates the size of a charged droplet to its mobility and find good quantitative agreement with our data when we calculate the size of the droplet which forms about the ion with classical macroscopic thermodynamic arguments. The radius thus obtained ranges from 7 to 9 Å.

We report results of computer simulations of a binary alloy on an fcc lattice, equivalent to an Ising system with a nearest-neighbor antiferromagnetic interaction $J>\mathrm{}0\mathrm{}$ and a next-nearest-neighbor ferromagnetic interaction $-\alpha J$, $\alpha >0\mathrm{}$. Our data indicate the existence of a discontinous change in energy and in sublattice magnetization as a function of temperature, for small $\alpha$. For $\alpha \gtrsim 0.25$, the transition appears to be continuous, suggesting a tricritical point at some intermediate $\alpha$.

The properties of the sound wave propagating in a superfluid two-phase system (liquid helium and its vapor) are investigated. At a frequency sufficiently low so that the superfluid helium and its vapor are in quasistatic equilibrium, there can propagate only one sound mode whose wave-guide-like velocity depends strongly on the vapor properties as well as the velocity of second sound. Near the $\lambda$ point, the mode probes the critical properties of the specific heat of the superfluid.

A parameter-free calculation of the equation of state for KCl and NaCl is presented which gives an accurate prediction of the equilibrium lattice constant over wide-ranging values of pressure and temperature. The results also show a lattice instability which is consistent with melting.

Using the time-of-flight atom-probe field-ion microscope, we have obtained an absolute composition depth profile of a Ni-Cu(5%) alloy, with single-atomic-layer resolution. The first-layer Cu composition is found to be (54.1±4.7)% on the (111) plane at 550°C. The Cu concentration of the near-surface layers is slightly lower as compared to the bulk. The composition returns to bulk value in about 5 atomic layers. Comparison of our result with those from other macroscopic techniques and existing theoretical models is also presented.