We report the first observation of the upper mode of surface polaritons in a three component layered structure composed of a GaAs film on a sapphire substrate. By changing the external medium from the air to benzene, we could detect a change in the dispersion relation. The observed dispersion of the upper mode agrees with theoretical predictions within the experimental uncertainty. The observation was made possible through the use of a digital background subtraction technique.

We have observed the generation of an electric field pulse by a nanosecond laser pulse incident on a bismuth surface in an external magnetic field. The propagation velocity and the de Haas-van Alphen-type oscillations are found to be consistent with those expected for Alfvén-wave propagation. This technique may well be a general way of exciting a variety of electromagnetic waves in a plasma.

We report measurements of the specific heat of paramagnetic U${\mathrm{Al}}_2$ between 0.8 and 25 K in magnetic fields up to 43 KOe. A nearly field-independent $T^3\ln T$ term dominates the temperature region below 10 K. The susceptibility was measured between 3 and 10 K and varies as $1-A{T}^2$. These results, and earlier resistivity measurements, are consistent with the predictions of the spin-fluctuation model. This is the first unambiguous observation of the specific heat predicted by the spin-fluctuation model for an atomically ordered paramagnet.

The amorphous ferromagnetic alloy ${\mathrm{Fe}}_{75}$${\mathrm{P}}_{15}$${\mathrm{C}}_{10}$ has been found to respond reversibly to magnetic annealing treatments. The response has been studied (a) by measurements of the $\Delta E$ effect, which is unusually large, (b) by measurements of the magnetostriction, and (c) by torque curves which yield a value of 550 erg/${\mathrm{cm}}^3$ for the uniaxial anisotropy parameter $K_u$. Internal-friction measurements reveal that the alloy is also susceptible to stress-induced ordering, with an activation energy of 2.2 eV.

Using Mössbauer spectroscopy, the order-disorder transition in stoichiometric ${\mathrm{Ni}}_3$Fe was investigated "at temperature" in the transition region between 770 and 785 K. Detailed analysis of the linewidth showed that the phase transition is of first-order character and proceeds inhomogeneously via the nucleation and growth mechanism. Nucleation of the ordered phase is suppressed, leading to a temperature hysteresis of 10 K. In the two-phase region composition segregation has been observed.

Magnetic excitations in the amorphous ferromagnet ${\mathrm{Co}}_4$P have been studied by use of neutron-inelastic-scattering techniques. Measurements around $Q=0\mathrm{}$ show distinct spin-wave excitations that obey a quadratic dispersion law $E=D{Q}^2$ where $D=185\mathrm{}$ meV ${\mathrm{\AA }}^2$. Additional measurements around the first peak in the static structure factor $S\left(Q\right)\mathrm{}$ show magnetic excitations that appear analogous to the roton excitations in ${}_{}{}^4{}_{}{}^{}\mathrm{He}$. These excitations are discussed in terms of sum rules for the magnetic scattering.

The nuclear charge distribution of fission products from ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}(n_{\mathrm{th}}, f)$ is determined for the isobaric chains 92 to 100. The results were obtained from the energy loss of monoisobaric and monoenergetic fission products in a $\Delta E$ Si surface-barrier detector. The odd-even effect is found also in the mass chains reported here for the first time, revealing an approximately sinusoidal variation of the charge distribution width with mass.

The spectrum of the night sky has been measured in the frequency range from 3 to 40 ${\mathrm{cm}}^{-1\mathrm{}}$ using a fully calibrated liquid-helium-cooled balloon-borne spectrophotometer at an elevation of 39 km. A model based on the known molecular parameters was used to subtract the atmospheric emission. In the frequency range from 4 to 17 ${\mathrm{cm}}^{-1\mathrm{}}$, the spectrum of the background radiation is that of a blackbody with a temperature of ${2.99}_{-0.14\mathrm{}}^{+0.07\mathrm{}}$ K.

A very narrow resonance with a mass of 3.105 GeV/${\mathit{c}}^2$ is observed in the reaction $\gamma +\mathrm{Be}\to {\mu }^{+}+{\mu }^{-}+X$. The total cross section for this process, as well as its $t$ distribution, is given.

A very narrow resonance with a mass of 3.1 GeV/${\mathit{c}}^2$ is observed in the reaction $n+\mathrm{Be}\to {\mu }^{+}+{\mu }^{-}+X$. The total cross section for this process, as well as its ${P_{\perp }}^2$ and $x$ distribution, are given.

The behavior of the $\overline{p}n$ annihilation cross section has been observed above and below threshold by studying annihilations in deuterium at low energies with a ± 2.5-MeV resolution. It varies inversely to the $\overline{p}n$ relative momentum except for a pronounced resonance with $(M, \Gamma )=(1897\mathrm{}\pm 1, 25\pm 6)$ associated with large proton momenta (200 to ∼ 300 MeV/c) and a narrower one (consistent with resolution) at ∼ 1932 MeV associated with lower (100-200 MeV/c) proton momenta. Since the production of these $I=1\mathrm{}$ states varies with the $\overline{p}n$ relative momentum their spins are not zero.

Results are given of a calculation of the self-energy radiative level shift of order $\alpha$ of the $2S_{\frac{1}{2}}$ and $2P_{\frac{1}{2}}$ states in a strong Coulomb potential. The shift is evaluated numerically to all orders in $Z\alpha$ for $Z$ in the range 10-110. An estimate is obtained for the effect of terms of high order in $Z\alpha$ on the Lamb shift in hydrogen. With this estimate taken into account, the theoretical value is $\mathcal{S}=1057.864\mathrm{}\left(14\right)\mathrm{}$ MHz.

An elaboration of solid-state NMR double resonance yields detailed molecular structural information residing in the dipole-dipole interactions between a rare spin and its nearest abundant-spin neighbors. The experiment depends upon (1) suppression of dipolar interactions among the abundant spins, and (2) observation of oscillatory interchange of magnetization between individual rare spins and their neighbors. Structural and dynamical information can be had even from powdered or amorphous samples.

The critical temperature gradients for the onset of convection and turbulence were measured in nematic para-azoxyanisole. The transition to turbulence was found to occur through two successive instabilities. The first of these clearly signals the entrance to a periodic-motion regime, and the second, although less clearly, to a regime with nonperiodic, time-dependent motion. A typical phase-transition behavior was observed at the transitions to turbulence.

The Van der Waals theory of surface tension and interface structure is extended to three-phase equilibrium. The theory predicts that near a tricritical point the three interfacial tensions will satisfy "Antonoff's rule" in the form ${\sigma }_{\alpha \gamma }={\sigma }_{\alpha \beta }+{\sigma }_{\beta \gamma }$, where $\beta$ is the distinguished phase, and that the composition profile of the $\alpha \gamma$ interface will be qualitatively different from that of the $\alpha \beta$ and $\beta \gamma$ interfaces.

The effective mass of the localized electron in dense helium gas at 4.2°K has been determined from measurements of space-charge-limited currents. We derive a value of about 3 helium masses from our results.

The direct trapping of positive He ions on quantized vortex lines in rotating He II has been observed at temperatures below 0.7 K. Trapping lifetimes have been measured between 0.1 and 0.7 K, and agree with models of thermal escape and charge loss from vortex motion. An ion radius of 7.7±0.1 Å is found.

The effect of mixing two high-power ruby-laser beams in a plasma has been investigated by means of light scattering. Coherently scattered light has been observed with intensities of up to 30 times that scattered by incoherent thermal fluctuations. As indicated by the wave-vector distribution, the nonlinear electromotive forces of the mixed electromagnetic waves produce a stationary electron-density wave in the plasma.

In the Alcator device incoherent Thomson scattering always gives Gaussian spectral profiles at low values of the ratio of electron drift velocity to thermal velocity ($\frac{v_D}{v_{\mathrm{th}}}\lesssim 0.1$). However, at higher values of $\frac{v_D}{v_{\mathrm{th}}}$ non-Gaussian profiles are observed and can be interpreted in terms of scattering from electrons with high toroidal velocity (low-energy runaways). This interpretation is supported by soft-x-ray and plasma-resistivity measurements and agrees with a previous theoretical analysis.

Spatial growth and damping of a velocity-modulated ion beam are observed in a $Q$ machine where no ion-ion instability is predicted. The phenomena are well explained by linear "wave" theory for beam bunching.