We report infrared spectra of defect-structure cubic compounds ${\mathrm{In}}_2$${\mathrm{Te}}_3$, ${\mathrm{Ga}}_2$${\mathrm{Te}}_3$, and ${\mathrm{Ga}}_2$${\mathrm{Se}}_3$. The spectrum of ${\mathrm{In}}_2$${\mathrm{Te}}_3$ with ordered vacancies is analyzed using sixfold folding of the first Brillouin zone of the zinc-blende structure in the [110] and [111] directions. It is shown that both folding models describe well the observed structure of the spectra of ${\mathrm{In}}_2$${\mathrm{Te}}_3$ with ordered or disordered vacancies.

Measurements on Al of the ratio of the photoyields by $p$- and $s$-polarized light, $\frac{Y_p}{Y_s}$, and the absolute yield for $p$-polarized light $Y_p$, at different angles of light incidence and at energies near photoemissive threshold, give results which are in excellent agreement with the strength of the surface photoelectric effect implied in recent calculations.

By means of $\gamma$-ray spectroscopy following (heavy ion, $\mathrm{xn}$) reactions, we have established a level scheme for the yrast states in ${}_{}{}^{186}{}_{}{}^{}\mathrm{Hg}$ up to the ${14}^{+}$ state. From the spectrum we conclude that ${}_{}{}^{186}{}_{}{}^{}\mathrm{Hg}$ makes a rather sudden angular-momentum-induced change in deformation from small values at low spins to rather large values at higher spins. This is in qualitative agreement with several potential-energy surface calculations, and leads to an interpretation of previously measured large isotopic shifts in rms radii from ${}_{}{}^{187}{}_{}{}^{}\mathrm{Hg}$ to ${}_{}{}^{183,185}{}_{}{}^{}\mathrm{Hg}$ as a sudden onset of stable quadrupole deformation.

An experiment is reported for measuring nuclear Zeeman splitting by use of the linear polarization of $\gamma$ radiation.

We have measured the cross section, the angular distribution, and the $\Lambda$ polarization for the reaction ${\pi }^{-}p\to \Lambda K^0$. A spark-chamber spectrometer was used to collect 8400 $\Lambda K^0$ events at fourteen beam momenta near $\Sigma K$ threshold. Our data do not show the prominent cross-section enhancement suggested by some previous experiments. However, detailed structure in the cross section and the angular distribution agrees well with a simple model which includes a cusp effect at $\Sigma K$ threshold.

In a study of nuclear collisions produced by 200-GeV protons in emulsion, we have found eight events attributable to the direct production of electron pairs by protons. A crude measure of the cross section, 6.7 ± 2.4 mb, is obtained. This result is viewed in relation to foregoing work on direct pair production by energetic leptons.

We report precision atomic-beam measurements which yield a value for the helium-hydrogen $g$-factor ratio: $\frac{g_J(\mathrm{He}, 2{}_{}{}^3{}_{}{}^{}S_1^{}{}_{}{}^{})}{g_J(\mathrm{H}, 1{}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{})}=1-23.25\mathrm{}\left(30\right)\mathrm{}\times {10}^{-6\mathrm{}}$ This value is in very good agreement with theory, and with an earlier, less precise atomic-beam measurement; it is in serious disagreement, however, with a recent optical-pumping determination which had seemed to cast doubt upon the adequacy of the theory.

A momentum anisotropy, created by injecting an electrostatically unneutralized annular electron beam through various foils, is shown experimentally to lead to high-power microwave emission. The radiation occurs at a frequency such that the phase velocities of cyclotron waves on the beam and the T${\mathrm{E}}_{01}$ mode in the guide are equal.

It is shown that the anomalous diffusion of a plasma across a strong external magnetic field may result from the hydrodynamic behavior of the plasma. The hydrodynamic contribution to the velocity-velocity correlation function is found to be proportional to $\frac{1}{B}$ for a magnetized plasma. It is suggested that classical calculations evaluate only what is essentially the microscopic part of the velocity-velocity correlations, and so do not give the $\frac{1}{B}$ contribution.

Oscillations of $p\mathrm{H}$ in an enzyme-catalyzed unbuffered hydrolysis reaction in a one-dimensional membrane are characterized by two parameters: the boundary substrate concentration, ${S_0}^{*}$, and a new phase transition parameter, $\zeta$ [Eq. (9)]. We present nonlinear computer simulations with and without a boundary layer, a linear theory for small amplitude oscillations without a boundary layer, and comments on recent experiments.

The transition temperature and the nature of the ordered state below it are calculated for solid orthohydrogen subject to quadrupole-type interactions. We introduce correlations similar to those in Lines's method, and obtain a transition temperature of 2.56°K, very near the observed 2.83°K.

We report an extensive set of experimental measurements on electric-field echoes in insulating and semi-insulating crystals. Previously suggested mechanisms cannot explain the results. In particular, three-pulse echoes with decay times $T_1$ of several hours have been observed at low temperatures in semi-insulating II-VI compounds. We propose a mechanism based upon the redistribution of trapped electronic space charge.

Brillouin scattering experiments have been performed between 1.7 and 300 K in glasses to demonstrate the existence of thermal phonons. The theoretically expected linear temperature dependence of the Brillouin peak intensities has been observed.

Similarities between diffusion of hot charge carriers in semiconductors and in gases are discussed, and formulas for $D_{\parallel }$ and $D_{\perp }$, the diffusion coefficients parallel and perpendicular to the applied electric field, are given. It is shown that anisotropy of diffusion can be strong even when the carrier distribution function is nearly isotropic in momentum space.

It is shown that anomalous dispersion of quasiparticles leads to nonpropagating states. Therefore regions of anomalous dispersion define a sort of "mobility gap." Using the coherent-potential approximation, we calculate the conditions for obtaining such a mobility gap in a disordered binary alloy. Just outside the mobility edges located at ${\omega }_c$ the mobility vanishes as $|\omega -{\omega }_c|$.

The time taken for the lowest ${}_{}{}^4{}_{}{}^{}T_1^{}{}_{}{}^{}$ excitons in Mn${\mathrm{F}}_2$ to scatter across the Brillouin zone, i.e., to lose all phase memory, has been measured using a technique of resonant optical pumping and monochromatic fluorescence detection. At 1.9 K these very narrow-band excitons retain some phase memory for up to 1 μsec. It is also found that excitons with rather well-defined momenta are created in the decay of exciton-magnon states, but not in the decay of exciton-phonon states. This determines probable decay mechanisms for these two-particle states.

The yrast levels have been determined to spin 16 and 18 in ${}_{}{}^{182,184,186}{}_{}{}^{}\mathrm{Os}$ and to spin 12 in ${}_{}{}^{188}{}_{}{}^{}\mathrm{Os}$ from $\gamma$-ray excitation functions, anisotropies, and coincidence data from the reactions ${}_{}{}^{182,184,186}{}_{}{}^{}\mathrm{W}(\alpha , 4n)$ and ${}_{}{}^{186}{}_{}{}^{}\mathrm{W}(\alpha , 2n)$. A fork is observed in the ${}_{}{}^{186}{}_{}{}^{}\mathrm{Os}$ yrast band at spin 12. Above spin 12 the $\mathcal{I}$-versus-${\omega }^2$ curves for ${}_{}{}^{182,184,186}{}_{}{}^{}\mathrm{Os}$ display "backbending" behavior. Such behavior has not been reported for any other nuclei with more than 96 neutrons.

We propose calculations and measurements of $N+d$ breakup cross sections as a function of a new set of kinematic variables. When carried out as a function of these variables, separable-potential calculations predict cross sections which exhibit a very deep destructive interference minimum over a wide range of bombarding energies. We proposed a procedure for isolating the effect of the crucial $M_{d2\mathrm{}}$ amplitude on the cross section.

We have studied the properties of decoupled bands in particular odd-$A$ nuclei, and the results provide information on the origin of backbending in even-even nuclei. Our data are in agreement with the rotation-alignment model and in apparent disagreement with the pairing-collapse model. This proposed test also provides a means to determine which particles are involved in the two-quasiparticle band that intersects the ground band in the rotation-alignment picutre of backbending.

166 events of the reaction $\nu +n\to {\mu }^{-}+p$ at an average neutrino energy of ∼ 0.7 GeV have been observed in the Argonne National Laboratory 12-ft deuterium bubble chamber. The results are well described by the conventional current-current weak-interaction theory with three real form factors ${F_V}^1$, ${F_V}^2$, and $F_A$. Using electron-nucleon scattering results to fix the vector mass $M_V$ at 0.84 GeV, and assuming a dipole form for $F_A$, we obtain the value 0.95 ± 0.12 GeV for the axial-vector mass $M_A$.