Structure in $\frac{d^{2}I}{d{V}^2}$, which corresponds to an increase in conductance at bias voltages equivalent to the surface plasmon energy in GaAs, is observed in $n$-type GaAs-Pb tunnel junctions. Its dependence on the electron concentration of the GaAs electrode has been studied. These data are consistent with the interpretation that the observed structure in $\frac{d^{2}I}{d{V}^2}$ is due to surface plasmon excitation in the GaAs electrode by tunneling electrons.

Sm${\mathrm{B}}_6$ has been found to show no magnetic ordering down to a temperature of 0.35°K. We interpret this to mean that the Sm ion is in its nonmagnetic divalent configuration at low temperatures and find direct evidence for the changing electronic configuration of Sm from trivalent to divalent with decreasing temperature in the observed semiconducting behavior at low temperatures.

The Raman spectra of high purity $o$-${\mathrm{H}}_2$ and $p$-${\mathrm{D}}_2$ at liquid-helium temperatures have been obtained. Features which appear below the ordering temperature are attributed to librational waves within the $J=1\mathrm{}$ manifold of states. On the basis of a comparison with recent theories of the ordered state, a new structure is proposed.

The presence of isospin coupling in the incident channel is observed as anomalous behavior in ${}_{}{}^{98}{}_{}{}^{}\mathrm{Mo}$+$p$ excitation functions for proton, deuteron, and triton outgoing channels. Similarly shaped anomalies are simultaneously observed in several channels at threshold energies for the ($p, n$) reaction to the ground-state analog and to excited-state analogs of ${}_{}{}^{98}{}_{}{}^{}\mathrm{Mo}$. The latter imply coupling through a deformation of the isospin-dependent potential.

Correlations between the measured strengths of excitation in the ($n, \gamma$) and ($d, p$) reactions on the $N=82\mathrm{}$ nuclei ${\mathrm{Ba}}^{138}$, ${\mathrm{Ce}}^{140}$, and ${\mathrm{Nd}}^{142}$ are discussed. The results are shown to be consistent with the common unique parent assumption of Lane and Wilkinson.

From observations of interstellar optical absorption lines of CN, CH, and C${\mathrm{H}}^{+}$ we are able to impose upper limits, at three wavelengths, on the intensity of background radiation in the interstellar medium. These limits are consistent with the existence of thermal background radiation at a temperature of ∼3°K, but can be reconciled with the results of a recent rocket observation by Shivanandan, Houck, and Harwit only if the intense flux which they report is concentrated into a sharp line which happens to avoid the molecular resonances, or if this flux is of local origin.

Position measurements of the Crab nebula pulsar NPO527 made with a split-beam antenna yield the position (1950) $\alpha ={05}^{\mathrm{h}}{26}^{\mathrm{m}}{10}^{\mathrm{S}}\pm {40}^{\mathrm{S}}$, $\delta =22\mathrm{}°0^{\prime }\pm {30}^{\prime }$. Thus NPO527 lies 1.2° from the pulsar NPO532, which is located at the nebula. The proximity and similar dispersion of these two pulsars suggest that they may have had a common origin in the supernova explosion of A.D. 1054 and hence that NPO527 is moving with a velocity of $\sim 0.15c$, a hypothesis which could be tested directly by proper motion measurements.

The muon range-energy relation indicated by experimental results of the Utah neutrino detector is presented. Difficulties arising from the observed isotropy in the muon flux are discussed.

We report the observation of an $s$-wave ${\pi }^0{\pi }^0$ enhancement at 715 MeV of width 150 MeV by the study of the reaction ${\pi }^{-}+p\to n+{\pi }^0+{\pi }^0$ in which the momentum of the neutron and the angles of the four gamma rays are all measured.

Muonic x rays in ${\mathrm{Pb}}^{206}$ were measured with high precision and in addition two of the weak transitions involving the $2s$ state were identified and measured for the first time. The new constraints make it difficult to fit the data with Dirac energies calculated for a finite nucleus and corrected for radiative effects. Consistency can, however, be achieved by depressing the calculated $1s$ energy by 6.8×2.3 keV, an effect tentatively interpreted as due to polarization of the nucleus by the muon.

We report the first ultrasonic, electron-paramagnetic-nuclear double-resonance experiment. This experiment was performed on Ca${\mathrm{F}}_2$:${\mathrm{U}}^{4+}$, and the results indicate that the ultrasonic-paramagnetic-resonance absorption line is inhomogeneously broadened due to superhyperfine interaction. These results are compared with a theoretical model for superhyperfine interaction in Ca${\mathrm{F}}_2$:${\mathrm{U}}^{4+}$.

We optically observe the untwisting and alignment, along an applied magnetic field, of high-pitch cholesteric liquid crystals, mixtures of para-azoxyanisole and cholesteryl esters. The results agree quantitatively with de Gennes's predictions and allow a determination of the twist elastic constant of pure para-azoxyanisole.

Measurements of the surface nucleation field $H_{c3\mathrm{}}$ and the bulk supercooling field $H_{\mathrm{sc}}$, made on pure tantalum, show that these fields are identical only when $\kappa <0.39\mathrm{}$, and that measurable supercooling occurs at all temperatures between $T_c$ and 1.4°K. The measurements verify qualitatively the recent theoretical work of Park. Nearly ideal supercooling of the bulk cylindrical samples is achieved by using small auxiliary-field coils to field coils to eliminate nucleation at the sample ends. A new value for the Ginzburg-Landau parameter of the pure metal ${\kappa }_0=0.340\mathrm{}\pm 0.01$ is derived from the data.

The thermodynamic potential of a metal with an arbitrary Fermi surface in the presence of a weakly nonuniform magnetic field is evaluated. From it an integral equation for the spatially varying magnetization is obtained, and its solutions are studied.

It is argued that the $\eta$ meson can be expected to play a significant role in generating three-body forces in nuclear matter. This seems to invalidate earlier conclusions, based on $\pi$ exchange, that the effect of three-body forces in nuclear matter is insignificant.

Calculation of the integrated electrofission cross section for ${\mathrm{U}}^{238}$, based on the known photofission cross section, shows that the photonuclear giant resonance can account for only about 15% of the cross section when the incident electron energy is large (≃500 MeV). The plane-wave approximation can be used; distortion of the electron wave functions produces less than 10% enhancement of the integrated cross section. Alternative mechanisms, which may contribute to electrofission, are introduced.

The lowest $T=2\mathrm{}$ level in the self-conjugate nucleus ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ has been observed in resonance reactions initiated by ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$+$\alpha$ ($\Delta T=2\mathrm{}$) but not in resonance reactions initiated by ${}_{}{}^{21}{}_{}{}^{}\mathrm{Al}$+$p$ ($\Delta T=1\mathrm{}$).

The reaction ${\mathrm{Li}}^6(p, p\alpha )d$ was studied as a function of angle at 61.5 MeV. The cross section was measured for ten proton angles. Using the quasifree knockout approximation, the ${\mathrm{Li}}^6(p, p\alpha )d$ angular distribution was compared with the free $p-\alpha$ elastic-scattering angular distribution. The agreement between the two is extremely good.

Electromagnetic effects of catastrophic processes are examples of physical phenomena in which the usual treatment of the Lorentz gauge gives incorrect results. The recently proposed new formulation of the Lorentz gauge leads to results identical to those of the Coulomb gauge.

Experimental distributions for the reaction $\mathrm{pp}\to \mathrm{pp}{\pi }^{+}{\pi }^{-}$ at 16 GeV/c are consistent with predictions of a Regge-pole model incorporating exchange of a Reggeized pion. The Treiman-Yang angle distribution affords a distinctive test in favor of pion Reggeization for this reaction.