We suggest a solution to the question of why isolated quark-partons are not observed. It is argued that gauge theories can have the light-cone behavior of quark fields without quark production in deep-inelastic reactions. Our ideas are illustrated in the exact solution of quantum electrodynamics in one space and one time dimension. The theory's crucial physical property is the extreme polarizability of its vacuum. Predictions for deep inelastic final states are presented.

The production of three pions in carbon via $I=0\mathrm{}$ exchange has been studied using the process ${\pi }^{-}\mathrm{C}\to {\pi }^{+}{\pi }^{-}{\pi }^{-}{\mathrm{C}}^{*}$, where $\mathrm{C}*$ is the $I=0\mathrm{}$, $J^P=2^{+}$ excited state of the carbon nucleus at 4.44 MeV. Preliminary results on the $3\pi$ mass distribution, the $t$ distribution, and the spin and parity states within the $3\pi$ system are reported.

A model in which partons scatter diffractively from hadrons is suggested which gives excellent fits to real and virtual photoabsorption and to the rise in the total $\mathrm{pp}$ cross-section. We discuss why a well-known sum rule diverges and show how it can be used to estimate $F_2\mathrm{}\left(0\right)\mathrm{}$.

Strong polarization effects have been observed in optical radiation from excited $J\ne 0$ states arising from low-energy ${\mathrm{Na}}^{+}$ -Ne collisions. In one case where radiation originates from a $J=1\mathrm{}$ to $J=0\mathrm{}$ transition, oscillations in the excitation function are found to be due exclusively to the polarization component of the radiation perpendicular to the beam direction. These are the first experimental observations of strong sublevel-state selection associated with collisional quantum-mechanical phase-interference phenomena.

The cross sections of projectile $K\alpha$ x radiation have been measured from energetic collisions of Ni and Br ions with targets throughout the periodic table. A strong enhancement in cross section is found when the binding energy of the $K$ or $L$ shell of the projectile matches approximately the $K$- or $L$-shell binding energy of the target atom. The data show that even at 1.6 MeV/nucleon, Coulomb excitation processes do not overwhelm molecular-orbital effects.

From photoelectron spectroscopic studies at 584 Å, the ${}_{}{}^2{}_{}{}^{}D_{\frac{5}{2}}^{}{}_{}{}^{}:{}_{}{}^2{}_{}{}^{}D_{\frac{3}{2}}^{}{}_{}{}^{}$ intensity ratios of Zn, Cd, and Hg have been determined, and the latter two were found to be significantly larger than the statistical value $\frac{\mathrm{}(l+1\mathrm{})\mathrm{}}{l}$. Earlier experiments on Ar, Kr, and Xe have yielded ${}_{}{}^2{}_{}{}^{}P_{\frac{3}{2}}^{}{}_{}{}^{}:{}_{}{}^2{}_{}{}^{}P_{\frac{1}{2}}^{}{}_{}{}^{}$ ratios smaller than statistical. We present Dirac-Slater calculations of the partial photoionization cross sections for the $J=l\pm \frac{1}{2}$ components of an atomic orbital which show that the ratio is larger or smaller than the statistical value depending on whether the partial cross sections are rising or falling.

We show that the Thomas-Fermi theory is exact for atoms, molecules, and solids as $Z\to \infty$.

High-resolution x-ray spectra have been used to obtain the relative intensities of transitions in fluorine ions that result from single collisions of ${\mathrm{F}}^{7+}$, ${\mathrm{F}}^{8+}$, and ${\mathrm{F}}^{9+}$ at 34.8 MeV in argon gas. Intensities of transitions resulting from direct electron capture to excited states have been compared to those produced by excitation processes. The importance of electron exchange in collisions in which inner-shell excitation occurs is indicated by the strong $(1s,2p)2{}_{}{}^3{}_{}{}^{}P_1^{}{}_{}{}^{}\to \left(1\mathrm{}{s}^2\right)1\mathrm{}{}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}$ transition obtained with incident two-electron ions.

The propagation of phonons in He II at 0.1 K, in the frequency range (2 to 9)×${10}^{10}$ Hz, has been studied using superconducting Al-film generators. Such superthermal waves ($\hslash \omega \gg \mathrm{kT}$) are shown to be long-lived propagating excitations in the liquid and to have negligible dispersion (group velocity varies by less than 0.5%). These measurements reveal that the current theories of phonon lifetimes in He II are inadequate.

The electron runaway rate in a uniform plasma under a uniform electric field is calculated by solving the Fokker-Planck equation numerically. Comparison with other theoretical and experimental results is made.

Heat-pulse experiments at 1.3 K show that the conversion of ballistic high-frequency phonons in a solid into second sound in superfluid helium can be used to study the transmission coefficient of the phonons through the interface. The transmission coefficients for longitudinal and transverse phonons in silicon are found to be equal for heater temperatures between 10 and 20 K.

Raman and Brillouin scatterings in inhomogeneous and blowoff plasmas are analyzed. For normal incidence, the threshold for near-90° Raman scattering is a minimum, necessitating the analysis without the WKB approximation. Pump depletion may severely limit the laser penetration into a plasma.

We have found a reversible temperature-induced explosive first-order electronic phase transition, with decreasing temperature at atmospheric pressure, in ${\mathrm{Sm}}_{1-x}{\mathrm{Gd}}_x\mathrm{S}$ for $0.16<~x<\mathrm{}0.22\mathrm{}$. The shiny golden-yellow metallic crystal disintegrates to a black powder. The transition is isostructural, but the unit cell expands from $a\approx 5.68 \mathrm{to} 5.82$ Å. The Sm ion in the black phase is characterized by an intermediate valence of ∼2.45. We present a phase diagram showing the stability regions in the $T-x$ plane and discuss a plausible driving mechanism for the transition.

A dynamic method for measuring the characteristic lifetimes and binding energies of physisorbed atoms is described and results presented. We find for ∼1.5 monolayers of helium adsorbed on Constantan an isosteric binding energy of 31 ± 1°K and a characteristic lifetime of (2 ± 0.5) × ${10}^{-7\mathrm{}}$ sec. The velocity distribution of the desorbing atoms is found to be non-Maxwellian.

Microscopic calculations of noble-gas adsorption on metals result in an ab initio determination of the interaction energy in agreement with available experimental data. An adequate determination of the attractive interaction energy using a local-dielectric-function formalism requires an accurate description of the dynamic polarizability of the incident atom. The repulsive contribution to the interaction energy was evaluated via the density-functional method. Systematics of He physisorption on various metals are reported.

The temperature dependence of multiphonon absorption in NaF, NaCl, and KCl was studied from room temperature to near the melting point at a wavelength of 10.6 μm. A large discrepancy was noted between the experimental results and those predicted using the usual expressions based upon temperature-dependent Bose-Einstein population factors and temperature-independent transition matrix elements.

Measurements of Harrington and Hass and of Barker indicate that the temperature dependence of the infrared absorption coefficient $\beta$ in the $n$-phonon region is considerably weaker than $\beta \sim T^{n-1\mathrm{}}$, which had been predicted for the high-temperature limit of multi-phonon absorption. This discrepancy is resolved by taking into account the temperature dependence of the phonon frequencies and the lattice constant. The agreement between the experimental and theoretical results with no adjustable parameters is good. A new evaluation of the multiphonon sums yields $\beta \sim \exp (-\omega \tau )$ directly, rather than as a sum on $n$.

The theory of infrared absorption by an array of independent, anharmonic oscillators is discussed. When the oscillator potential is the Morse potential, the theory provides an excellent description of the temperature dependence of the absorption coefficient at 10.6 μm in NaCl and NaF reported by Harrington and Hass.

Interference between Coulomb and nuclear excitations for inelastic deuteron scattering has been observed for a number of nuclei. Most data are in qualitative, although not quantitative, agreement with collective-model distorted-wave Born-approximation predictions of constructive Coulomb-nuclear interference; excitation functions for the first $2^{+}$ states of $N=82\mathrm{}$ nuclei, however, show destructive interference not predicted by the collective model.

The reactions ${}_{}{}^9{}_{}{}^{}\mathrm{Be}(t, {}_{}{}^6{}_{}{}^{}\mathrm{Li}){}_{}{}^6{}_{}{}^{}\mathrm{He}$ and ${}_{}{}^9{}_{}{}^{}\mathrm{Be}(t, {}_{}{}^6{}_{}{}^{}\mathrm{Li}_{}^{*}{}_{}{}^{}){}_{}{}^6{}_{}{}^{}\mathrm{He}$ have been measured at a bombarding energy of 23.5 MeV. The reaction products ${}_{}{}^6{}_{}{}^{}\mathrm{He}$(ground state), ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$(ground state), and ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$(3.56 MeV) are members of a spin-isospin supermultiplet, and the observed differential cross sections are dominated by a symmetry expected from such considerations. Significant deviations from symmetry are, however, seen, especially in the isospin-multiplet channel.