An optical emission process is observed in which a ${\mathrm{Cr}}^{3+}$ ion, initially in the ${}_{}{}^2{}_{}{}^{}E_{\mathrm{g}}^{}{}_{}{}^{}$ excited state, simultaneously emits a photon and excites a neighboring ${\mathrm{Eu}}^{3+}$ ion to an excited ${}_{}{}^7{}_{}{}^{}F_J^{}{}_{}{}^{}$ level. Transitions terminating on $J=1\mathrm{}$ through 5 have been found.

A substantial enhancement of the photoluminescence of $p$-GaP and a shift to shorter wavelengths have been observed at 27 and 4°K, after the application of a voltage pulse of sufficient magnitude to raise the current appreciably above the value extrapolated from low fields. The current rises abruptly above a critical voltage. The observations are explained in terms of a model based on impact ionization of holes bound to isolated acceptors.

A strongly anisotropic ultrasonic donor-spin resonance has been observed in Asdoped Ge. The anisotropy is consistent with the theoretical formula for the isolated donors.

Alloys of Sc with magnetic impurities show strong anomalies in the concentration dependence of the impurity interaction temperature. This is interpreted with exchange enhancement of the susceptibility of metallic Sc near a finite wave vector.

We have studied the temperature dependence of the electrical resistivity of palladium-iron alloys in the composition range 0.5-12 at.% Fe with particular emphasis on the neighborhood of the magnetic-ordering temperature. Values of the critical temperature $T_c$ determined from the temperature of the maximum of $\frac{d\rho }{\mathrm{dT}}$ fall consistently below those obtained from saturation-magnetization measurements. The dependence of $T_c$ on Fe concentration is discussed and correlated with other properties of this system.

A comparison of the number of neutrons emitted as a function of fragment mass is reported for 8.5- and 13.0-MeV proton-induced fission of ${}_{}{}^{233}{}_{}{}^{}\mathrm{U}$. Results indicate that the excitation energies of the light fragments do not change appreciably, while those of the heavy fragments increase with increasing incident energy. The increase in fragment excitation for masses of ∼132 amu ($Z\cong 50$, $N\cong 82$) is significantly greater than that in compound-nucleus excitation and is accompanied by a decrease in fragment kinetic energy.

An attempt is made to understand the relationship between the experimental $B(E2;I_i\to I_f)$ values for different nuclei in the first half of the $1f-2p$ shell in terms of the structure of the intrinsic single-particle orbits resulting from deformed Hartree-Fock calculations for these nuclei.

The new statistical model due to Griffin has been extended to include charged-particle emission by evaluation of the transition matrix in terms of a relative velocity and scattering cross section. Additionally a quite different formulation is derived for the equilibrium emission probability, whereas the precompound emission probability is similar to Griffin's result.

We present results of detailed spin- and isospin-dependent analyses of $\mathrm{pd}$ and $p-{}_{}{}^4{}_{}{}^{}\mathrm{He}$ elastic-scattering intensities, polarizations, and total cross sections. The basic nucleon-nucleon scattering amplitudes used yield nucleon-nucleon observables in excellent agreement with measurements, including those of the elastic-scattering intensity, polarization, and spin correlation. Contributions of multiple scatterings, including multiple charge-exchange collisions, produce considerable structure in the predicted polarizations.

It is argued that a sufficiently fast, charged, nongravitating particle would radiate strongly in a classical gravitational field. Subject to some assumptions, the possibility that the muon does not couple to gravitation is ruled out on the basis of existing data.

Approximately 12 000 four-pronged interactions of 22-GeV/c protons in a hydrogen bubble chamber have been measured. In a sample of 1234 $\mathrm{pp}{\pi }^{+}{\pi }^{-}$ events the final state is dominated by ${\Delta }^{++}\mathrm{}\left(1236\right)\mathrm{}$ production. Approximately 120 of these events are attributed to the $p{\pi }^{+}{\pi }^{-}$ decay of a resonant state with mass 1443 ± 15 MeV and width 100 ± 25 MeV identified with the $N_{\frac{1}{2}}^{}{}_{}{}^{*}\mathrm{}\left(1400\right)\mathrm{}$ resonance. There is also strong evidence for a $p\pi \pi$ enhancement with a central mass value of 1693 MeV.

A strong enhancement is observed in the $\Lambda {\pi }^{-}$ mass spectrum in the reaction $K^{-}d\to \Lambda {\pi }^{-}p$; the central mass of the enhancement is at 1440 MeV, near $\overline{K}N$ threshold. The enhancement may be explained in one of two ways: (1) as being due to a "moving triangle singularity", or (2) as being due to an $I=1\mathrm{}$ resonance strongly coupled to the $\Lambda \pi$ system.

High-energy elastic scattering and diffraction-dissociation data are shown to provide evidence for the factorizability (within 25%) of the Pomeranchuk singularity.

We point out the suitability of rare-earth ions in singlet ground states for the production of very low temperatures by means of nuclear adiabatic demagnetization. We have observed nuclear cooling in PrBi from an initial temperature of 0.026°K to a final temperature of 0.01°K.

Experiments performed with an rf-induced gas discharge demonstrate the existence of neutral atoms with sufficient energy to cause secondary emission of electrons. Evidence is presented that these energetic neutrals are produced by ion neutralization and reflection at the target electrode surface.

Experimental results are presented which show that spatial plasma wave echoes exist with frequencies above the cyclotron frequency and below the plasma frequency. A theory predicting cyclotron-harmonic wave echoes under the foregoing conditions is found to be consistent with observations.

Measurements are presented of the thermal conductivity at saturated vapor pressure of 1.3 and 5.0% dilute solutions of ${\mathrm{He}}^3$ in superfluid ${\mathrm{He}}^4$ over the approximate temperature range 0.035-0.5°K and of pure superfluid ${\mathrm{He}}^4$ over the temperature range 0.04-0.16°K. Heat transport is primarily by ${\mathrm{He}}^4$ phonons whose paths are limited by the ${\mathrm{He}}_3$-quasiparticle-${\mathrm{He}}^4$-phonon interaction and by boundary scattering, in qualitative agreement with a theory of thermal conduction in dilute solutions by Baym and Ebner. There is, however, quantitative disagreement with their calculation of the thermal conductivity for the above solutions.

Second-sound attenuation very near $T_{\lambda }$ is found to be proportional to the square of the frequency, and the damping diverges as ${(T_{\lambda }-T)}^{-\sigma }$, $\sigma =0.34\mathrm{}\pm 0.06$, in agreement with dynamic scaling. The coefficient of the damping is consistent with recent estimates of the coherence length.

Magnetically coupled tin films are found to exhibit the characteristic dc transformer effect first reported by Giaever only for reduced temperatures of the primary $0.925<t<\mathrm{}1\mathrm{}$. A striking dependence of the secondary voltage on magnetic fields is also observed. The temperature dependence of the depinning current and the critical current is discussed.

The effect of a dc voltage to cause an alternating current through the barrier between two superconducting regions was predicted on theoretical grounds by Josephson. It is shown for the simplified geometry of a thin ring, interrupted by a single barrier, that this effect can be interpreted as a direct consequence of general principles which are closely related to those previously employed to explain the quantization of trapped flux.