Results valid in the long-wavelength limit for the angular dependence of all the spin-wave and plasma-wave modes of an electron liquid are presented. Experimental study of the angular dependence should yield a very accurate estimate of differences between successive coefficients in the expansion of the Fermi-liquid interaction function.

The absorption of transverse ultrasonic waves in superconductors shows peaks rising considerably above the normal-state attenuation level when the temperature is near that of the superconductor-normal phase transition, $H\ne 0$, and the phonon polarization $\overrightarrow{\epsilon }$ satisfies specific boundary conditions. The observations are found to be consistent with a model attributing the enhanced absorption to a loss mechanism associated with relaxation of the Ginzburg-Landau order parameter.

Superconductivity has been detected in a high-pressure phase of cerium at pressures higher than 50 kbar. This is the first example of a pure metal which, in different crystallographic phases, shows both magnetic ordering and superconductivity. The important question again arises whether the "collapsed" $\alpha$ phase will become superconducting at a certain pressure.

It is suggested that consideration of misfit dislocations is essential for analysis of mobility in metal-oxide-semiconductor inversion layers. Occurrence of such dislocations is generally expected for interfaces. Also, aspects of "surface" state behavior fit well with the dislocation model.

We introduce a simple model Hamiltonian for the study of phase transitions in perovskite compounds $\mathrm{AB}{\mathrm{O}}_3$ involving rotations of $B{\mathrm{O}}_6$ octahedra. Depending on the relative magnitude of the anharmonic coefficients, we find a transition to the tetragonal or to the trigonal phase. We obtain the temperature dependence of the rotation angle below the transition temperature $T_a$, and of the soft-mode frequencies associated with the transition both above and below $T_a$. The coupling to an elastic deformation field is briefly discussed.

A magnetic-dipole-active local mode has been observed in Mn${\mathrm{F}}_2$:${\mathrm{Fe}}^{2+}$ at 94.8 ${\mathrm{cm}}^{-1\mathrm{}}$ by means of far-infrared spectroscopic techniques. For a magnetic field parallel to the $c$ axis of the crystal, the absorption line shows a linear splitting. A $g$ factor of 2.3 is derived from the data.

The Brillouin-scattering spectrum of K${\mathrm{H}}_2$P${\mathrm{O}}_4$ has been studied over the temperature range $118°\mathrm{K}<T<\mathrm{}300\mathrm{}°\mathrm{K}$ with particular emphasis on the region close to the ferroelectric transition at 122°K. Results in the paraelectric phase are analyzed in terms of the piezoelectric coupling of the acoustic $X_y$ shear mode to the ferroelectric soft mode. Results in the ferroelectric phase indicate that the transition is better described by the Slater-Takagi-Senko model than by Cochran's model.

The energy spectra of fast photoprotons from ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ have been measured for a bremsstrahlung energy between 50 and 80 MeV. The analysis of the obtained cross section shows a strong direct emission from the $1p$ shell.

We have observed a strong backward peak in the differential cross sections of backward-hemisphere $\overline{p}p$ elastic scattering in the momentum range 300-700 MeV/c. The differential cross section near 180° and near 90° shows energy-dependent fluctuations. A consistent interpretation of these fluctuations can be made in terms of direct-channel boson resonances with masses and widths $m_r,{\Gamma }_r$, in MeV, of (∼1925, ∼10) and (1945, ∼20), and a state with mass greater than ∼1975 MeV and width greater than 20 MeV.

A test of time-reversal invariance for an electromagnetic interaction at high momentum transfer has been performed by measuring the recoil-deuteron vector polarization for the elastic scattering of electrons from an unpolarized deuteron target for an incident electron energy of 1 GeV and a recoil-deuteron four-momentum of $q=721\mathrm{}$ MeV/c. The value obtained for the vector polarization is $\mathrm{}\left|P\right|=0.075\mathrm{}\pm 0.088$, showing no significant $T$ nonconservation.

We report on an experimental study of the reaction ${\pi }^{+}d\to {\pi }^0{\pi }^0\mathrm{pp}$ at 2.15 BeV/c for $\mathrm{}\left|t\right|<10\mathrm{}{\mu }^2$, with emphasis on the measurement of the absolute $2{\pi }^0$ cross section. A direct comparison with ${\pi }^{+}{\pi }^{-}$ production at the same energy is made. In addition, comparison with the analysis of Malamud and Schlein provides support for the one-pion-exchange model as well as support for a large $T=0\mathrm{}$, $l=0\mathrm{}$ $\pi \pi$ phase shift in the $\rho$ mass region.

Electrons have been scattered inelastically from an alcohol-water target containing protons polarized normal to the scattering plane. Scattered-electron energies corresponding to the excitation of the 1236-, 1512-, and 1688-MeV nucleon resonances were observed at four-momentum transfers between 0.2 and 0.7 ${(\mathrm{B}\mathrm{e}\mathrm{V}/\mathit{c})}^2$. A search was made for changes in the intensity of the scattered electrons as the target polarization was reversed. None was seen.

Elastic scattering of $K^{+}$ mesons from protons in the backward direction has been measured to high accuracy. The data indicate that baryon exchange is extremely important for $P_{\mathrm{lab}}\mathrm{}\left(K\right)>1.8\mathrm{}$ GeV/c. A phase-shift analysis of the data suggests the existence of a $P_{\frac{1}{2}}$ resonance in the $K^{+}p$ system at a mass of approximately 2 ${\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c}}^2$.

An energy-dependent phase-shift analysis in the kaon laboratory-momentum range below 2.0 BeV/c has been made of $K^{+}p$ scattering data, supplemented by information from $K^{+}p$ forward dispersion relations. Evidence for a possible resonance in the $P_{\frac{1}{2}}$ state is presented.

The differential asymmetry ratio for the process $\gamma +n\to p+{\pi }^{-}$ was measured at 90° in the center-of-mass system and for incident photon energies from 352 to 550 MeV. The observed asymmetries are larger than the values predicted from the theory by Berends, Donnachie, and Weaver. A smaller $M_1$- amplitude gives better agreement between the experiment and the theory.

A more explicit version of Schwinger's formula is given, and it is observed that the spin-dependent mass splitting between the octuplet and decuplet is governed by the same linear functional form as the isospin-hypercharge-dependent splitting within either unitary multiplet.

To test the assumptions which underlie them, four finite-energy sum rules are evaluated for $\pi N$ scattering. Results are obtained for three choices of end point: ${\mathrm{}\left(1356\mathrm{M}\mathrm{e}\mathrm{V}\right)\mathrm{}}^2$, ${\mathrm{}\left(1808\mathrm{M}\mathrm{e}\mathrm{V}\right)\mathrm{}}^2$, and ${\mathrm{}\left(2313\mathrm{M}\mathrm{e}\mathrm{V}\right)\mathrm{}}^2$. For the intermediate end point all four sum rules work. However, for the highest one they all fail. The results are interpreted as confirming the assumptions of analyticity and Regge behavior, but pointing to the limitations of the resonances-dominance approximation.

It is shown that the Nambu-Han model of integrally charged quarks can account for both ${\pi }^0\to 2\gamma$ and $\eta \to 2\gamma$ decay rates with a suitable specification of $0^{-}$ and $1^{-}$ meson states in "charm" space.

Splittings of atomic core $p_{\frac{3}{2}}$ levels caused by internal electric field gradients have been observed in compounds of Th, U, and Pu by means of photoelectron and internal-conversion spectroscopy. The magnitude of the splitting varies with the element and specific compound examined, and it may be considerably enhanced by application of a strong external field.

The energy of electrons released in collisions of metastable rare gas atoms with various gases is measured by means of a retarding potential field. The energy distributions obtained show a marked influence of the interaction forces between the colliding particles.