Using third-sound resonance, we find for helium film thickness less than 2.8 atomic layers that there exist excitations which are phononlike and two dimensional, obeying a $T^3$ law, that their areal density is independent of film thickness, and that their velocity (using Landau theory) is 76±2 m/sec. This velocity is slightly above the maximum thirdsound velocity, 69 m/sec, that can be attained by ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ on argon. For thicker films the areal density of these excitations becomes smaller.

Changes $\frac{\Delta C}{C}$ in sound velocity $C$ in liquid helium-4 over the frequency range 1 to 15 MHz were studied as a function of temperature for $0.45>~T>~0.1$ K. The experimental results are in qualitative agreement with predictions of positive phonon dispersion for small momentum values.

We present measurements of large transverse resonance frequency shifts in NMR studies on superfluid $B$-${\mathrm{He}}^3$ contained in narrow channels separated by flat Mylar sheets. From these shifts we determine the orientation of the anisotropy axis with respect to the external field, and show that it is accurately determined by existing theory. We discuss the field dependence of the resonance shifts and present several new theoretical results which allow us to determine $H_B{R}_C$ from our data.

For an electromagnetic wave obliquely incident on an inhomogeneous plasma, the dominant instability at critical density is a radiating decay instability whose associated ion-wave frequency, even in regimes where the growth rate greatly exceeds the real frequency, is approximately ${\left({{\lambda }_{\mathrm{D}}}^{2}L\right)}^{-\frac{1}{3}}{c}_s\equiv K_{min}{c}_s$. The stimulated radiation peaks between the normal and backscatter angles and may be an important factor in explaining present experiments. A nonlinear calculation at modest power shows that the nonlinear state involves a large-amplitude ion wave through which the excited waves can compress the pump wave.

We investigate the turbulence excited by an ion beam in an unmagnetized plasma in connection with the linear theory of the ion-beam—plasma instability. Depending on beam velocity, one- or three-dimensional turbulence can be expected. These two types are experimentally observed by looking at space correlation functions.

A one-parameter scaling function $s\left(x\right)\mathrm{}$ of $x=k\xi$, where $\xi$ is the correlation length and $k$ the wave number of a density or concentration fluctuations in a fluid, is derived from a phenomenological field theoretic approach. On the basis of a positive-definite spectral function, we exploit the requirements of a three-particle threshold and the correct asymptotic approach as $x\to \infty$. The resulting $s\left(x\right)\mathrm{}$ is compared with the Fisher-Burford approximant obtained from numerical studies of the three-dimensional Ising model.

Measurements of the linear expansion coefficient $\alpha$ of pure vitreous silicas and ULE (Corning) silica at liquid-helium temperatures indicate a linear term analogous to that observed in the specific heat of glasses. This term, $x\approx -0.10\mathrm{}\times {10}^{-8\mathrm{}}T$ ${\mathrm{K}}^{-1\mathrm{}}$, leads to a large Grüneisen parameter $\gamma$ between - 40 and - 50, suggestive of a tunneling process.

We report the first synthesis of chemically pure polymeric sulfur nitride [${\left(\mathrm{SN}\right)}_x$]. The optical reflectance of well-characterized films of this polymeric solid has been measured from the near ultraviolet (30 000 ${\mathrm{cm}}^{-1\mathrm{}}$) to the far infrared (500 ${\mathrm{cm}}^{-1\mathrm{}}$). Metallike reflectance is observed in the infrared through the visible region with a well-defined plasma minimum near 22 000 ${\mathrm{cm}}^{-1\mathrm{}}$, corresponding to light polarized parallel to the polymer chain axis. The Drude-Lorentz model is used to analyze the data, and the physical implications of the resultant parameters are discussed.

A new second-order light scattering process has been observed which yields line spectra at frequency shifts ${\omega }_{\mathrm{LO}}\pm {\omega }_{\mathrm{SF}}$, where ${\omega }_{\mathrm{LO}}$ is a longitudinal optical-phonon frequency, and ${\omega }_{\mathrm{SF}}$ is an electron or hole spin-flip frequency. The scattering is highly resonant, and the proposed mechanism is analogous to that for multiple-phonon line spectra and double spin-flip scattering.

We report on the observation of the ${}_{}{}^{16}{}_{}{}^{}\mathrm{N}_{}^m{}_{}{}^{}\left(0^{-}\right)\to {}_{}{}^{16}{}_{}{}^{}\mathrm{O}(\mathrm{g}.\mathrm{s}.\mathrm{})$ $\beta$ decay. The comparison of the measured decay rate, 0.43±0.10 ${\sec }^{-1\mathrm{}}$, with the rate of the inverse muon-capture reaction in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ yields for the induced-pseudoscalar form factor: $13<~g_P\left(q^2\simeq {m_{\mu }}^2\right)<~20$. Subject to the approximations of the analysis and neglecting possible second-class currents, this result indicates an upward renormalization of this form factor in nuclei.

Polarization and ($p, p^{\prime }\gamma$) angular-correlation studies near isobaric analog resonances in proton scattering from ${}_{}{}^{92}{}_{}{}^{}\mathrm{Mo}$ and ${}_{}{}^{106}{}_{}{}^{}\mathrm{Cd}$ indicate strong correlations between compound-nuclear decay channels. A modified Hauser-Feshbach formula which includes correlations among these channels which belong to the analog resonance can explain the data.

It is pointed out that a formulation commonly used to describe mixed-isospin nuclear resonance is incorrect. An alternative approach is suggested and applied to some examples.

An investigation of the reaction ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}(d, d^{\prime })$ at $E_d=46\mathrm{} \mathrm{and} 70$ MeV has demonstrated significant advantages in studying isoscalar giant resonances with deuterons compared with other projectiles. The differential cross section at 70 MeV for the resonance at $E_x\approx 63A^{-\frac{1}{3}}$ MeV provides strong evidence for an $E2\mathrm{}$ interpretation. A comparison of measurements in ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}(d, d^{\prime })$ and ($p, p^{\prime }$) provides evidence for excitation of the giant dipole resonance by protons.

Data for the $\alpha$-particle pickup reaction ($d$, ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$) have been obtained at 35-MeV bombarding energy for even-even nuclei from ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ to ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$. The cross sections for the transitions to the ground states decrease approximately as $\frac{1}{{A_t}^3}$ where $A_t$ is the target mass. $\alpha$-particle transfer probabilities have been extracted from the data and are found to be substantially enhanced in heavy nuclei away from shell closures, particularly for deformed nuclei near $A\approx 150$. $\alpha$-particle correlations appear to be related to two-nucleon pairing effects.

For a system of noninteracting fermions in a local potential with no discontinuous edges, an explicit series in the expansion parameter ${\hslash }^2$ is derived for the "smooth" part of the energy. The method is based on the semiclassical partition function developed by Wigner and Kirkwood. Numerical calculations are done for spherical and deformed Woods-Saxon potentials. Comparisons are made with other methods, and in particular the numerical accuracy of the Strutinsky smoothing is tested.

The product of the photoproduction cross section at 11.1 GeV for $\psi \mathrm{}\left(3105\right)\mathrm{}$ on nucleons times the branching ratio for $\psi$ into $e^{+}{e}^{-}$ is less than 75 pb, at the 90% confidence level. This result implies a $\psi$-nucleon total cross section of less than 1.2 mb.

The reactions $e^{+}{e}^{-}\to e^{+}{e}^{-}$ and $e^{+}{e}^{-}\to {\mu }^{+}{\mu }^{-}$ have been measured at center-of-mass energies 3.0, 3.8, and 4.8 GeV and production angles of $50°<\theta <130\mathrm{}°$ over all azimuthal angles. Agreement with quantum electrodynamics is excellent. New limits for cutoff parameters in quantum-electrodynamic-breakdown models are given.

We derive SU(4) mass formulas taking mixing, whenever it arises, fully into account. With the masses of the usual hadrons and that of the newly discovered resonance $\psi$ as input, we predict the masses of the new $1^{-}$ and $0^{-}$ mesons as well as the ${\mathrm{½}}^{+}$ and ${\frac{3}{2}}^{+}$ baryons.

Intensity oscillations are observed in the quasimolecular $K$ x-ray spectrum emitted in high-energy ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$-${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$ collisions. The oscillating structure is shown, theoretically, to reflect the existence of a two-step mechanism for the production of molecular-orbital $K$ x rays in which sudden rearrangements of molecular-orbital populations are produced by vibrations between atomic and molecular orbitals of $K$-hole states during the interpenetration of the electronic clouds.

The attenuation of 20-MHz zero sound in superfluid $A$-${}_{}{}^3{}_{}{}^{}\mathrm{He}$ has been studied as a function of angle between the sound propagation direction and an applied magnetic field, and found to be anisotropic.