The lifetimes of excitons bound to neutral donors in GaP and Si were measured to be much shorter at low temperatures than predicted from absorption measurements. An Auger recombination process in which one bound electron recombines with the bound hole while exciting the second bound electron into the conduction band is believed to predominate over radiative recombination.

Sum and difference frequency generation are observed when visible laser light is mixed in GaP with each of five infrared laser frequencies near the reststrahl. The measured infrared frequency dependence of the nonlinear susceptibility, which varies by a factor of 60, is accounted for by theory.

A Ge(Li) detector has been used to observe de-excitation $\gamma$ rays from ${\mathrm{O}}^{15}$ and ${\mathrm{N}}^{15}$ following the photodisintegration of ${\mathrm{O}}^{16}$ at giant resonance energies. Significant branching to the (${\mathrm{½}}^{+}$, ${\frac{5}{2}}^{+}$) states near 5 MeV implies a departure from a single-particle, single-hole $E1\mathrm{}$ absorption process.

Data obtained with semiconductor detectors and a particle-identifier system on fragments ejected from uranium bombarded with 5.3-GeV protons show that ${}_{}{}^{11}{}_{}{}^{}\mathrm{Li}$, ${}_{}{}^{14}{}_{}{}^{}\mathrm{B}$, and ${}_{}{}^{15}{}_{}{}^{}\mathrm{B}$ are particle stable, ${}_{}{}^{10}{}_{}{}^{}\mathrm{Li}$ is particle unstable, and ${}_{}{}^{13}{}_{}{}^{}\mathrm{Be}$ is most probably particle unstable.

A comparison is made between theoretical and experimental results for the lowest ${}_{}{}^1{}_{}{}^{}S$ and ${}_{}{}^3{}_{}{}^{}P$ resonances for the $e$-H scattering system.

A new model for the kinetics of thermal oxidation of metals is presented which is based on the hypothesis that the rate-limiting step is thermal excitation of electrons or electron holes over Schottky-type barriers in a diffusion-controlled electric field created by the ionic species.

We report a simplification of the Landau theory, permitting more direct prediction of compatible space groups in second-order phase transitions. The theory is applied to the ${\mathrm{V}}_3$Si transition, to predict that the lower symmetry space group is either ${C_{4v}}^7-P4\mathrm{mc}$ or ${D_{2d}}^5-P\overline{4}m2\mathrm{}$. The former possibility admits a polar axis.

We have applied the assumptions of simple additivity of quark amplitudes and SU(2) invariance to derive relations among hadron total cross sections, assuming hadrons to be composites of integral charge particles. Our results are compared with those obtained from the conventional quark model.

We report operation of apparatus to measure the Fourier transform of the Riemann curvature tensor at sensitivity limited by the thermal fluctuations. The gravitational interaction drives a mechanical system which in turn is coupled to the electromagnetic field. Strains as small as a few parts in ${10}^{16}$ are observable for a compressional mode of a large cylinder.

It is shown that the observed energy spectrum of cosmic-ray electrons between 1 and 350 GeV may be compatible with the existence of a universal blackbody radiation at 3°K, in contrast to the conclusion drawn by Daniel and Stephens in a recent Letter.

Further evidence for the $H$ meson is presented. The decay angular distributions are found to be consistent with $J^P=1^{+}$.

The optical densities of states of Co and Pd have been determined. As with the other $3d$ ferromagnetic metals, Ni and Fe, Co is found to have the "anomalous" peak about 5 eV below the Fermi level. No such peak is present in Pd.