Quarks of charge $\frac{1}{3}e$ and $\frac{2}{3}e$ have been searched for in air showers of energies between ${10}^{13}$ and ${10}^{15}$ eV. A hodoscope of proportional counters was placed under 15 cm of Pb. Scintillation counters on top of the lead triggered on high-multiplicity showers. No quark was detected in 2120 h. The upper limit of the quark flux in showers between ${10}^{14}$ and ${10}^{15}$ eV is, with 90% confidence, 1.0 × ${10}^{-10\mathrm{}}$ ${\mathrm{cm}}^{-2\mathrm{}}$ ${\sec }^{-1\mathrm{}}$ ${\mathrm{sr}}^{-1\mathrm{}}$ for either charge.

The fractional shift in the electronic gyromagnetic ratio in muonium is calculated as -7.8±2.3 ppm under Kr pressure of 230 psi at 30°C. Together with the experimental data of The University of Chicago Group, we obtain the values $\frac{{\mu }_e}{{\mu }_{\mu }}=206.766\mathrm{}70\left(93\right)\mathrm{}$ for the electron to muon magnetic moment ratio, $\frac{{\mu }_{\mu }}{{\mu }_p}=3.183\mathrm{}349\mathrm{}\left(15\right)\mathrm{}$ for the muon to proton magnetic moment ratio, $\frac{m_{\mu }}{m_e}=206.767\mathrm{}96\left(95\right)\mathrm{}$ for the muon to electron mass ratio, and ${\alpha }^{-1\mathrm{}}=137.036\mathrm{}46\left(36\right)\mathrm{}$ for the inverse fine-structure constant.

The adiabatic-nuclei theory is shown to be quantitatively applicable to vibrational excitation of diatomic molecules by electron impact. When the dependence of the fixed-nuclei phase shifts on internuclear separation is approximated by a two-term Taylor series, the resulting formulas are transparent and easily evaluated. Application to $e-{\mathrm{H}}_2$ excitation is made, phase-shift derivatives are estimated, and the theory is found to fit experimental data.

We have observed experimentally the parameteric excitation of ion acoustic waves and cyclotron harmonic waves by a high-frequency electric field with frequencies near the harmonics of the cyclotron frequency. We have verified both the wave-vector and the frequency selection rules. The measured threshold fields and growth rates are in good agreement with theory.

Intense microwave emission was detected when a pulsed relativistic electron beam traversed a spatially modulated magnetic field. The microwave intensity was $\gtrsim 70$ dB above the noise level. The wavelength of the electromagnetic radiation was equal to the characteristic length of the rippled magnetic field. At a critical averaged magnetic field, the radiation appeared to be almost monochromatic ($\frac{\Delta \lambda }{\lambda }\lesssim 0.5\%$); below the critical field, a broad spectrum appeared ($\frac{\Delta \lambda }{\lambda \gtrsim 10\%}$).

Our measurements show at $\frac{E}{P}<0.03\mathrm{}$ V/Torr cm a decrease of the drift velocity in hydrogen with increasing pressure (up to 50 000 Torr), which cannot be explained by an electron trapping mechanism. It is shown that this effect is in agreement with Legler's theory which takes into account multiple scattering. For $\frac{E}{P}>0.03\mathrm{}$ V/Torr cm, the observed decrease of the drift velocity can be explained by an electron trapping mechanism.

As a simple model for investigating the stability of an electrostatic plasma wave with trapped electrons, the plasma is regarded as a nonlinear, dispersive dielectric. A non-linear Schrödinger-type equation is found, which predicts instability for both electron plasma waves and ion acoustic waves. These instabilities do not depend on resonance with the bouncing motions of the trapped electrons, and thus have a different physical origin than those predicted by bunched-beam models.

A wave spectrum peaked in angle and broadened in wave number is found from a non-linear saturation theory for the decay-type parametric instability in the case of nearly equal electron and ion temperatures. The dominant saturation mechanism is nonlinear damping of Langmuir waves by induced scattering from ions. The nonlinear resistivity for transverse waves, including the pump, is obtained from the related mechanism of conversion of transverse into longitudinal waves due to interaction with ions.

We report calculations of the transition temperatures of superconducting colloids. We find that if the colloidal particles are of less than a certain critical size, they do not affect the transition temperature of the matrix (which may be positive or zero). Some colloidal systems exhibit multiple transition temperatures, going from the normal to the superconducting state and then back to the normal state as the temperature is progressively lowered.

The behavior of the zero-bias anomaly in $p-\mathrm{S}\mathrm{i}:\mathrm{B}$ Schottky-barrier tunnel junctions subjected to large static uniaxial stress is found to correlate with the stress-induced changes in the overlap of the impurity wave functions in the vicinity of the Mott transition.

The spectrum of light scattered quasielastically by a single crystal of succinonitrile has been studied using an optical heterodyne technique. Both the spectral width and relative intensity of the spectrum indicate that the classical theory of Rayleigh scattering from fluids is also valid for scattering from a crystal.

We report stimulated emission associated with Zn-O-complex recombination transitions in GaP:Zn-O and with NN-pair lines in $\mathrm{Ga}{\mathrm{As}}_{1-x}{\mathrm{P}}_x:\mathrm{N} \mathrm{}(x=0.56\mathrm{})\mathrm{}$. Laser operation (cw, 77°K) characteristic of inhomogeneously broadened transitions is exhibited clearly by NN-pair lines in GaAsP and probably occurs for Zn-O pairs in GaP.

Planar clusters of interstitials in alkali halides, giving rise to dislocation-loop contrast, have been studied using transmission electron microscopy. These loops are produced together with $F$ centers by ionizing radiation. It seems very likely that they consist of planar aggregates of $〈110〉$-aligned halogen molecules.

This is a report of the first Brillouin scattering measurements on silicon and germanium. The measurements were made at $\lambda =6328\mathrm{} \mathrm{and} 4880$ Å at which frequencies the optical absorption lies in the range ${10}^4$ to 6×${10}^5$ ${\mathrm{cm}}^{-1\mathrm{}}$. As a result of the high absorption, the light sees only a few wavelengths' extent of the phonon, and so from the uncertainty principle the Brillouin peaks become very broad. The measured linewidths have been analyzed to give the real and imaginary part of the refractive indices. Good agreement is obtained with the values reported in the literature.

Critical exponents are calculated for dimension $d=4-\epsilon$ with $\epsilon$ small, using renormalization-group techniques. To order $\epsilon$ the exponent $\gamma$ is $1+\frac{1}{6}\epsilon$ for an Ising-like model and $1+\frac{1}{5}\epsilon$ for an $\mathrm{XY}$ model.

The directions of the easy magnetization in the ${\mathrm{Ho}}_x{\mathrm{Tb}}_{1-x}{\mathrm{Fe}}_2$ system have been determined by means of the Mössbauer effect in ${}_{}{}^{57}{}_{}{}^{}\mathrm{Fe}$. If the direction of magnetization of the system is described by an ($x,T$) spin-orientation diagram, it is found that the ($x,T$) plane is divided into three regions, in each of which the direction of magnetization is along a different major crystal axis. The diagram is interpreted by simple cubic-crystallinefield theory.

The nuclei ${}_{}{}^{15}{}_{}{}^{}\mathrm{N}$, ${}_{}{}^{15}{}_{}{}^{}\mathrm{O}$, and ${}_{}{}^{19}{}_{}{}^{}\mathrm{Ne}$ are examined in terms of the appearance of $\alpha$-particle core-excited threshold states. It is shown that this simple model can account for most of the $\alpha$-particle states seen above the threshold for $\alpha$-particle emission. We discuss the most striking features of these states.

A new method of determining nuclear shapes is proposed which avoids the assumption of a specific nuclear model. The concept of an equivalent ellipsoid, whose charge and moments equal those of the nucleus, is employed. But the method is equally valid for spherical, deformed, and intermediate nuclei. It can be employed for any nucleus (evev-evevn, odd-$\mathbf{A}$, or odd-odd) provided enough $E2\mathrm{}$ matrix elements are available. The example of ${}_{}{}^{152}{}_{}{}^{}\mathrm{Sm}$ is discussed.

The sensitivity of a dumbbell gravity-wave antenna is compared with that for a cylindrical detector. It is concluded that a Weber cylindrical antenna is decidedly the more sensitive at mutually accessible frequencies, particularly if the detector is to operate at higher frequencies in addition to the fundamental. A dumbbell antenna does offer the possibility of sampling the very low-frequency end of the spectrum which is inaccessible to cylinders.

We have studied the production mechanism of the reaction $K^{-}p\to \Sigma \mathrm{}\left(1385\right)\mathrm{}\pi$ with the total energy in the vicinity of the $\Lambda \mathrm{}\left(1520\right)\mathrm{}$ resonance. Two different analysis techniques were used: partial waves and moments. The results establish the decay mode $\Lambda \mathrm{}\left(1520\right)\mathrm{}\to \Sigma \mathrm{}\left(1385\right)\mathrm{}\pi$. Conclusions on ${\frac{3}{2}}^{-}$ octet-singlet mixing are presented.