Pion-production cross sections have been measured for the reaction ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}+{}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}\to {\pi }^{+}+X$ at a laboratory energy of 1.05 GeV/nucleon. A maximum in the ${\pi }^{+}$ cross section occurs at mid-rapidity, which is anomalous relative to $p+p$ and $p$+nucleus reactions and compared to many other heavy-ion reactions. Calculations based on cascade and thermal models fail to fit the data.

Pulsed beams of ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ and ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ were used to determine $g$ factors of eight isomeric states in ${}_{}{}^{144,146,147,148}{}_{}{}^{}\mathrm{Gd}$ by the time-differential spin-rotation method. The results show that proton and neutron configurations contribute about equally to the generation of angular momenta of two high-spin yrast isomers in ${}_{}{}^{146,147}{}_{}{}^{}\mathrm{Gd}$ ($I\sim 19 \mathrm{and} \frac{49}{2}$) whose detailed quasiparticle structure is suggested.

${\pi }^{\pm }$ electroproduction from ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ has been studied at 90° (laboratory) for $T_{\pi }\simeq 17 \mathrm{and} 29$ MeV. Transitions to discrete final states in ${}_{}{}^{12}{}_{}{}^{}\mathrm{B}$ and ${}_{}{}^{12}{}_{}{}^{}\mathrm{N}$ were observed up to 4.5-MeV excitation energy. The results are analyzed using virtual-photon theory. The resulting photoproduction cross sections are in reasonable agreement with recent theoretical calculations.

The excitation function of the reaction ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$(${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$)${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$(g.s.) has been measured at the second maximum of the angular distributions (${\theta }_{\mathrm{lab}}\simeq 5°$) from 39- to 65-MeV incident energies. Oscillatory structure in the excitation function is observed with peak-to-valley ratios equal to ∼1.5. The angular distributions measured near the maxima of the excitation function decrease more rapidly toward large angles than squares of Legendre polynomials, suggesting a direct reaction process to be important. Standard distorted-wave Born-approximation calculations do fit the angular distributions quite well, but fail to reproduce the structure in the excitation function.

The reactions ${}_{}{}^{10}{}_{}{}^{}\mathrm{B}$($p$,${\pi }^{+}$)${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$(g.s.) and ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$($p$,${\pi }^{+}$)${}_{}{}^{41}{}_{}{}^{}\mathrm{Ca}$(g.s.) have been studied with proton beams in the energy range 140 to 200 MeV. Angular distributions at several energies, supplemented with fixed-angle cross-section data at several other energies, establish for the first time the energy dependence of these reactions in the near-threshold region.

The cross section for absorption of 125-MeV positive and negative pions in Li, C, Al, Fe, Nb, and Bi was measured. The results were obtained by combining a transmission experiment, a measurement of the angular distribution for pion scattering, and an estimate of the charge-exchange cross section. Information about inelastic scattering and decomposition of the total pion-nucleus cross section into its contributions from the major channels is also obtained.

Experimental nuclear-polarization corrections for muonic ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ have been deduced from a model-independent analysis of elastic electron-scattering and muonic x-ray data. The result is in disagreement with theoretical calculations and suggests the existence of a fundamental problem in present theoretical approaches to the nuclear polarization effect.

Collision-induced Raman spectra of helium at 30 amagats are obtained, with incident beam polarization parallel and perpendicular to the direction of observation. The comparison reveals the presence of a polarized continuum not seen before in any gas. A wave-mechanical computation of this polarized spectrum, utilizing as input an ab initio calculation of the trace of the helium diatom polarizability, agrees with the observation. Thus a second, independent measurement of the isotropic part of the diatom polarizability is obtained.

Pronounced angular-dependence effects have been observed in the elliptic polarization and intensity of ${\mathrm{H}}_{\alpha }$ radiation following low-energy grazing-incidence collisions of protons on a clean nickel single crystal (110) maintained under ultrahigh vacuum. Polarization variations, measured for the first time from a single crystal, correlate with variations in electron density along the particle trajectory.

By following the orbits of several thousand particles in their self-consistent spacecharge fields, the evolution of an unstable Kapchinskij-Vladimirskij distribution is examined until saturation is reached. A distribution is formed which is stable on a scale of hundreds of quadrupole magnets.

Increased ultrasonic attenuation is found in ${\mathrm{As}}_2$${\mathrm{S}}_3$ glass at 4.2 K after removal of a high electric field. The extra attenuation persists for a few minutes before disappearing, but can be reduced, or practically eliminated, by infrared radiation of moderate intensities. The effect is attributed to atomic relaxation accompanying electronic transitions in gap states where injected carriers have been trapped. The gap states may be valence-alternation pairs.

We have used Fermi-surface pressure-derivative measurements at 2 K and singlecrystal and powder x-ray studies as a function of pressure at room temperature to demonstrate that recently published anomalous Fermi-surface and lattice properties of Re${\mathrm{O}}_3$ are related to a novel second-order phase transition. This transition probably involves a tetragonal distortion of the lattice accompanying a displacement of the O atoms from the linear O-Re-O chains of cubic Re${\mathrm{O}}_3$ to a "hinged" arrangement at the oxygens and is characterized by an enormous increase in the compressibility of the high-pressure phase.

In ${\mathrm{Ce}}_c{\mathrm{La}}_{1-c}{\mathrm{F}}_3$ we have observed frequency shifts of optical phonons depending on the concentration $c$ of the $4f$ ions and on temperature. It is shown that these effects are due to a resonant $4f$-electron-phonon interaction via photon-induced virtual quadrupole transitions to excited crystal-field states of ${\mathrm{Ce}}^{3+}$. These shifts are related to the magnetic phonon splitting of doubly degenerate phonons. Both effects can be quantitatively interpreted with the same coupling constant.

The Anderson model of localization in two dimensions is studied with use of a numerical implementation of real-space renormalization-group transformations. A critical parameter $\frac{W}{V}$ is found which separates localized and extended behavior, the latter being characterized by scaling toward strong coupling.

We present a theory of the saturation of inter-valence-band absorption in $p$-type Ge by high-intensity light with a wavelength near 10 μm. The absorption coefficient decreases with intensity in a manner closely approximated by an inhomogeneously broadened two-level model. The saturation intensity is calculated as a function of excitation wavelength and temperature and found to be in good agreement with measured values.

A theory of non-Ohmic conduction from depinning of charge-density waves by an electric field is presented. It is based on Zener-type tunneling of the charge-density waves across a gap at the Fermi surface that is determined by the pinning frequency. The theory applies to relatively pure specimens for which the pinning is due to approach to commensurability or cooperative action of impurities.

An analysis of $g-2\mathrm{}$ and lifetime measurements for electrons and muons at various velocities is used to compare the transformation of time, electromagnetic field, and mass in moving coordinate systems and to check the Thomas precession. The data are in good agreement with the special theory of relativity.

We report a verification of the theory of special relativity at a value of $\gamma \approx 2.5\times {10}^4$ based upon a comparison of electron $g-2\mathrm{}$ measurements at meV and GeV kinetic energies. Specially we obtain a measure of the equivalence between the quantities $\gamma \equiv {(1-{\beta }^2)}^{-\frac{1}{2}}$ and $\tilde{\gamma }\equiv \left(\frac{p}{m_0}\right)\frac{\mathrm{dp}}{\mathrm{dE}}$.

Using Monte Carlo techniques, we evaluate the path integral for the four-dimensional lattice gauge theory with a $Z_2$ gauge group. The system exhibits a first-order transition. This is contrary to the implications of the approximate Migdal recursion relations but consistant with mean-field-theory arguments. Our "data" agree well with a low-temperature expansion and the exact duality between the high- and low-temperature phases.

It is shown that the "forbidden" asymmetries in $p-p$ bremsstrahlung, suggested by Moravcsik as a source of off-shell information, contain also large on-shell effects, which are suppressed by just one power of the photon momentum $k$, relative to such effects in other observables. Two separate criteria—large off-shell parameter $\Delta m^2$ and large soft-photon parameter $\frac{k}{E_0}$—are emphasized as necessary for a geometry which enhances off-shell effects.