High-resolution inelastic electron-scattering cross sections from ${}_{}{}^{207}{}_{}{}^{}\mathrm{Pb}$ have been measured in the range of momentum transfer $0.37 {\mathrm{fm}}^{-1\mathrm{}}<~q<~2.30 {\mathrm{fm}}^{-1\mathrm{}}$. Form factors have been extracted for low-lying neutron hole states and some one-particle, two-hole states. Models for the induced charge of the neutron are compared with the data.

Measurements of the double-electron-transfer cross section ${\sigma }_{1-1}$ for the formation of ${\mathrm{N}}^{-}$ at 35 and 124 keV gave values less than ${10}^{-22\mathrm{}}$ ${\mathrm{cm}}^2$. The formation of this negative ion indicates that either it has a cross section much smaller than suggested by theory, or the ${\mathrm{N}}^{-}$ formed by gas-phase double electron transfer has a lifetime less than 50 ns.

Intense green emission bands are observed when potassium vapor in several amagats of xenon is illuminated with the 4067-Å line of a krypton-ion laser. The very pronounced dependence of this green band on temperature and xenon density is consistent with the behavior expected for $\mathrm{K}{\mathrm{Xe}}_n$ exciplexes with $n$ ranging from 1 to at least 4.

We have observed a well-resolved Condon diffraction pattern in the ${0_u}^{+}\left(\nu \approx 57\right)\to {0_g}^{+}\mathrm{}\left(\mathrm{unbound}\right)\mathrm{}$ fluorescence of ${\mathrm{Hg}}_2$. The upper state is excited by photoassociating mercury atoms with an ArF laser at 193 nm.

A model for the rate of density rise observed when neutral gas is fed into the plasma chamber is presented for regimes where known collisional transport processes do not provide an adequate explanation. A dense layer of cold plasma produced at the edge of the plasma column and the resulting ion-temperature gradient, sharper than the relative density gradient, can lead to the excitation of electron temperature fluctuations driven by ion drift modes. These can induce a net inflow of electrons and ions under realistic conditions.

Measurement of spatial profiles of self-generated magnetic fields in Nd: glass-laser-produced pla$\stackrel{\mathrm{`}}{\mathrm{s}}$mas have been made with high temporal and spatial resolution (30 ps, 1.5 μm) by simultaneous Faraday rotation and interferometry using a Raman-shifted second-harmonic probe beam.

A new branch of solutions of the finite-beta drift-wave radial eigenmode equations has been found. The branch is heavily damped in the low-beta regime and identified with the shear Alfvén wave. This branch and the usual electrostatic branch are damped in a collisionless plasma. Including trapped electron effects introduces an instability which is potentially harmful to plasma confinement.

The large zero-sound attenuation just below the transition temperature $T_c$ to a superfluid state in liquid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ is anticipated above the transition by an excess attenuation over that for a normal Fermi liquid. The excess is greatest at $T_c$ but can be readily discerned at temperatures several percent above $T_c$. The excess is largest near melting pressure and exists adjacent to both ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-$A$ and ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-$B$.

We have observed a variety of thermorotation effects, effects involving thermal counterflow in rotating superfluid helium. In particular, the temperature and chemical-potential gradients associated with the motion of vortex lines have been measured.

Using mean-field theory we compute the frequency-integrated neutron cross section $I(q,T)\mathrm{}$ for spin-glasses. We find, as observed experimentally, that the temperature of the maximum of $I(q,T)\mathrm{}$ depends on the momentum transfer $q$ and is different from the freezing temperature $T_c$ at which the susceptibility $\chi \mathrm{}(q,T)\mathrm{}$ has a cusp. These results suggest that recent neutron scattering experiments are consistent with a sharp phase transition at a single temperature $T_c$ in spin-glasses.

Well-characterized transforming (T) and nontransforming (NT) ${\mathrm{V}}_3$Si single-crystal samples have been investigated under hydrostatic pressures up to 29 kbar. Above the critical pressure $P_c$, the superconducting transition temperature $T_c$ of the T sample was found to increase continuously with pressure, with only a reduction in $\frac{\partial T_c}{\partial P}$. The value of $\frac{\partial T_c}{\partial P}$ for the T sample above $P_c$ is similar as to that for the NT sample. A pressure-induced phase transition in the NT sample at 28.6 kbar was observed. The results are discussed and compared with some of the predictions of various models on $A15$ high-$T_c$ superconductors.

A peak was observed in the $I-V$ characteristic of silicon $p-i-n$ diodes at liquid-helium temperatures when the voltage was changed rapidly in the reverse-bias direction. The size and structure of the peak were dependent upon the integrated incident light, or forward injection. The intrinsic rise time of the peak was found to be less than 0.3 nsec.

The electronic charge density for ${\mathrm{Nb}}_3$Ge and ${\mathrm{Nb}}_3$Al is calculated using a self-consistent pseudopotential technique. Results indicate that there is charge transferred from Nb and Ge to the interstitial region, suggesting a metallic bonding description of these compounds. The charge transfer from Ge to Nb is not prominent as suggested by the Bongi model. Calculated charge densities for states near the Fermi level suggest that $R$ and $M$ are more sensitive to atomic displacements along the chain than the points $\Gamma$ and $X$ chosen previously to explain $A-15\mathrm{}$ Martensitic transitions.

The first ultraviolet photoemission spectra of the valence electrons of rare-gas atoms, implanted by ion bombardment into an amorphous Ge matrix, are presented here. The positions of the peaks in the observed spectra are shifted relative to gas-phase spectra, consistent with a final-state screening-energy shift which varies inversely with the radius of the particular implant, as predicted by a linear-response relaxation model described herein.

In the presence of interactions which violate both $P$ and $T$ invariance, a ferroelectric crystal with electric polarization $\overrightarrow{\mathrm{P}}$ and appreciable nuclear spin polarization, suspended in a magnetic field $\overrightarrow{\mathrm{H}}$, will experience a torque of the form $\overrightarrow{\mathrm{P}}\times \overrightarrow{\mathrm{H}}$. The maximum torque density in PbTi${\mathrm{O}}_3$ compatible with existing limits on such interactions is estimated at a few times ${10}^{-6\mathrm{}}$ erg/${\mathrm{cm}}^3$. Some obvious "nuisance" effects are estimated and the theoretical sensitivity of such an experiment discussed.

In the ionic molecular crystal ${\mathrm{K}}^{+}$C${\mathrm{N}}^{-}$, excitonic properties characteristic of both ionic and molecular crystals are observed at different photon energies. Various molecular exciton interactions are manifested in the low-energy part of the spectrum. A resolved Davydov-type splitting is observed for the first time in an ionic crystal and is explained by a weak-interaction model. Charge-transfer excitons occur at higher energies.

We have observed the cosmic-ray ${\mathrm{Be}}^7$/Be ratio to be 0.6 below 500 MeV/nucleon, as expected from spallation reactions, but then to drop sharply to 0.4 by 1500 MeV/nucleon. This measurement suggests that primary cosmic rays traverse some material at their sources, producing ${\mathrm{Be}}^7$ which picks up electrons and decays by $K$ capture during or after the acceleration to relativistic energies. All cosmic rays then enter interstellar space, where further pickup is negligible.

The method of Bäcklund transformations is employed to derive in 2 + 1 and 3 + 1 dimensions exact solutions of the sine-Gordon equation $[{\nabla }^2-c^{-2\mathrm{}}(\frac{{\partial }^2}{\partial t^2}\left)\right]\chi =sin\chi$. A formula is developed in 3 + 1 dimensions which permits us to generate without additional quadratures an infinite class of new time-dependent solutions.

Quantitative estimates of the single-$\gamma$ and $-\pi$ emission rates for transitions between bound states of the nucleon-antinucleon system are presented. Quantum-number assignments in the context of potential and baryonium models are suggested for new mesons recently seen in monoenergetic $\gamma$ emission from the $\overline{p}p$ atom. It is shown that $\pi$ transitions are important in distinguishing between alternative models.

The differential decay rates of $\mu \to e\gamma \gamma$ for the most general local interaction are presented. It is shown that recently published data on $\mu \to e\gamma$ imply an upper limit on the branching ratio for $\mu \to e\gamma \gamma$ of 5 × ${10}^{-8\mathrm{}}$ with 90% confidence. This is almost two orders of magnitude better than the existing experimental limit. Gauge models which allow a larger rate for $\mu \to e\gamma \gamma$ than for $\mu \to e\gamma$ are discussed.