High-power microwave radiation is observed when a positive pulse is applied to an anode of a reflex triode. The frequency of radiation varies as $f\sim \frac{V^{\frac{1}{2}}}{D^n}$, where $V$ is the anode voltage, $D$ is the cathode-virtual-cathode spacing, and $0<n<~1$. The basic features of the radiation are explained by a theoretical model which predicts particle bunching as a result of the energy dependence of the electron oscillation frequency.

Extensive air-shower trajectories and sizes (numbers of charged particles) have been measured using an optical detection system at Volcano Ranch Station near Albuquerque, New Mexico. Light produced by atmospheric scintillation and Cherenkov emission by shower particles was measured at distances of 0.7 to ∼ 10 km. The shower sizes determined by the optical measurements are in satisfactory agreement (an average of 10% higher) with measurements by the ground-level scintillation-counter array at Volcano Ranch.

We measured $\frac{d\sigma }{\mathrm{dt}}$ for $p+p\to p+p$ at 11.75 GeV/c using the zero-gradient synchrotron 70% polarized-proton beam and a 65% polarized-proton target. We obtained the spin-orbit asymmetry parameter $A$ and the spin-spin correlation parameter $C_m$ out to ${P_{\perp }}^2=4.2\mathrm{}$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$. We found that $A$ drops smoothly towards zero, but that $C_{\mathrm{nn}}$ increases abruptly near ${P_{\perp }}^2=3.6\mathrm{}$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$, where the $\exp (-1.4\mathrm{}{P_{\perp }}^2)$ component of elastic scattering becomes dominant. This suggests that large-${P_{\perp }}^2$ "hard" elastic scattering may occur mostly when the two proton spins are parallel.

The total cross section for hadron production by high-energy photons has been measured from a number of nuclei ranging from hydrogen to uranium. Some shadowing is observed at a level considerably less than predicted by conventional vector-meson dominance but consistent with a modified theory. The energy dependence predicted by vectormeson dominance is observed. The shadowing in heavy nuclei shows a smooth transition from electroproduction to photoproduction.

We present results on flux-normalized neutrino and antineutrino cross sections near $y=0\mathrm{}$ from data obtained in the Fermilab narrow-band beam. We conclude that values of ${\sigma }_0={\frac{d\sigma }{\mathrm{dy}}|}_{y=0\mathrm{}}$ are consistent with rising linearly with energy over the range $45<~E_{\nu }<~20.5$ GeV. The separate averages of $\nu$ and $\overline{\nu }$, each measured to 4%, are equal to well within the errors. The best fit for the combined data gives $\frac{{\sigma }_0}{E}=(0.719\mathrm{}\pm 0.035)\times {10}^{-38\mathrm{}}$ ${\mathrm{cm}}^2$/GeV at an average $E_{\nu }$ of 100 GeV.

In the relativistic-electron-coil-Christa experiment two separate, strong $E$ layers ae are generated from a single beam pulse, and then combined by moving one of the layers along the tank axis. The "stacking" of two layers with about half of the field-reversal strength each leads to the generation of single $E$ layers with field-reversal strength.

Experiments on strong $E$ layers trapped in a magnetic mirror field, $B_0$, indicate anomalous fast-particle losses when quadrupole Ioffe field components, $B_Q$, are added. These losses include both loss bursts at critical field-reversal levels $\delta \equiv \frac{\delta B}{B_0}$ of ∼ 25% and ∼ 50% (independent of $B_Q$ and gas pressure) and enhanced steady-state losses between and above these levels. The anomalous loss rate normalized to the normal collisional loss rate is independent of the background pressure, but roughly proportional to $B_Q$ with no evident threshold.

When the input irradiance $I$ exceeds a threshold value, two mechanisms cause the stimulated Raman scattering by a plasma to increase as $\exp \left(g_E{I}^{2}x\right)$. One mechanism is a nonlinear increase in the plasmon amplitude, and the other is a second-order process of converting two laser photons into a Stokes photon and anti-Stokes photon. In laser fusion, the enhanced scattering by the residual fusion-chamber gas may greatly reduce the laser irradiance at the target. This theoretical possibility should be investigated experimentally.

It is shown that trapped-electron-induced scattering can be dominant over nonlinear ion Landau damping in the saturation of short-wavelength, dispersive, trapped-electron instabilities in tokamaks. Trapped-electron-induced scattering transfers the wave energy to shorter wavelengths, where it can be dissipated by ion viscosity.

A model allowing the calculation of very high-$\beta$ tokamak equilibria with choice of $\beta$, ${\beta }_p$, and $q_0$ is described. One of these equilibria having $\beta =12\%$ has been shown to be stable to low-$n$ internal modes.

A procedure is described for the experimental determination of phase relationships among x-ray reflections from single crystals. It is shown that when three or more sets of planes diffract simultaneously, the spatial distribution of reflection intensities becomes a sensitive function of the reflection phases. The dynamical theory of diffraction accounts satisfactorily for the intensity variations and is used to establish phase relationships directly from the intensity data.

The ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ nuclear-quadrupole resonance (NQR) data of Seliger et al. on the smectic-VI and -$H$ phases of terephtal-bis-butylaniline are reanalyzed and compared to neutron results. For the smectic-VI phase, both methods lead to remarkably consistent conclusions, but do not differentiate between possible models. For the $H$ phase, the NQR results are consistent both with a model permitting weak orientational order around the long axis and with a model permitting uniform rotation around the long axis plus (anisotropic) fluctuations of this axis. The latter is more realistic since it agrees with the neutron results while the former does not.

An exact relation is established between the solid-on-solid model describing the growth of crystals and the classical $\mathrm{XY}$ model. Application of this relation to a special case leads to an exact correspondence between the $\mathrm{XY}$ model and the Coulomb gas which matches with the relation obtained by Kosterlitz in the strong-coupling limit.

We present data on the low-energy satellites of the donor-bound—exciton luminescence in silicon doped with Li, P, and As with stress applied along the $〈100〉$, $〈111〉$, and $〈110〉$ directions. The satellite lines show identical behavior under stress as the principal bound exciton. The highly anisotropic features and a specific "fine structure" of the spectra place severe constraints on any model for interpretation of the lines. Comparison with recent experiments on acceptor-bound excitons (Al and Ga) in silicon casts doubt on the existence of multiple excitons bound to donors.

We present detailed electronic structure, total- and orbital-density-of-states information for an ordered overlayer of oxygen on Al(100). Our calculations show that $\mathrm{O}\mathrm{}\left(2p\right)\mathrm{}$ levels are split upon chemisorption. We attribute the oxygen-related structure reported in photoemission experiments to $\mathrm{O}\left(2\mathrm{}{p}_{\sigma }\right)$ levels broadened by band-structure and crystalfield effects. The $\mathrm{O}\left(2\mathrm{}{p}_z\right)$ levels are predicted to disperse significantly due to hybridization with the substrate and may be observable in angularly resolved photoemission experiments.

I account for the magnitude and temperature dependence of the mobility of TTF-TCNQ in the range 150-300 K by scattering of the carriers by optical phonons derived from the symmetric molecular vibrations. The only adjustable parameters are the widths of the conduction bands on TCNQ and TTF chains, chosen as 3000 and 1500 K, respectively. I also obtain estimates of the coupling to acoustic phonons and the unbroken chain lengths by fitting conductivity data down to 70 K.

Proton polarization of approximately 65% has been achieved with the University of Massachusetts "spin refrigerator" in a nonuniform 1.07-T field at 1.25 K. The free protons in (Yb, Y) ${\left({\mathrm{C}}_2{\mathrm{H}}_5\mathrm{S}{\mathrm{O}}_4\right)}_3$ · 9${\mathrm{H}}_2$O are polarized through sample rotation at 100-200 rps. Results represent the first confirmation of high polarization predicted by a single-Yb-ion interaction model since the original proposals of Jeffries and Abragam. The polarized-proton target, with length equivalent to 9 cm of liquid hydrogen, will be utilized in studies of strange particles.

A nonequilibrium single-scattering mechanism is proposed to describe the inclusive proton spectrum from relativistic heavy-ion collisions. Data from ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ + U and ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ + U collisions are shown to be consistent with a simple model of the knock-out process. Two-proton azimuthal angle correlations are suggested as a unique signature of this reaction mechanism.

The ${}_{}{}^{192,194,196}{}_{}{}^{}\mathrm{Pt}$ nuclei were Coulomb excited with ${}_{}{}^{136}{}_{}{}^{}\mathrm{Xe}$ projectiles. Strong excitation of the ground-state band (up to spin ${10}^{+}$) and the "$\gamma$" band (up to spin $8^{+}$) were observed. Excitation of the upper members of the $\gamma$ band is shown to be sensitive to the $\gamma$ softness. The observed Coulomb-excitation yields imply $B\left(E2\mathrm{}\right)\mathrm{}$ values which follow the rigid-triaxial-rotor relation. This contradicts current calculations which predict considerable $\gamma$ softness.

The effect of the operator causing one-nucleon transfer in heavy-ion reactions in the molecular-orbital (MO) approach is contrasted to that of the usual distorted-wave Born approximation in a simple diffraction model calculation. For the case of $\Delta l=1\mathrm{}\hslash$ transitions, it is shown that the MO approach predicts an angular distribution exactly out of phase with that of the distorted-wave Born approximation. The MO approach therefore offers a simple explanation of the "anomalous" angular distributions recently observed.