Starting from a $T$-odd Lagrangian involving the nucleon, meson, and electromagnetic fields interacting at a point, we calculate the one-meson-exchange diagram and obtain the longest-range part of a two-nucleon electromagnetic operator. Even if this interaction were present with "maximal" strength, we would not expect $T$-invariance violation to have been seen in any of the existing $E2\mathrm{}-M1\mathrm{}$ interference experiments including ${}_{}{}^{36}{}_{}{}^{}\mathrm{Cl}$ which has the smallest gap between model and experiment.

We calculate the ${\eta }^{\prime }\to \eta \pi \pi$ decay rate, assuming that SU(3)⊗SU(3) symmetry is of the Goldstone-Nambu type and that the symmetry-breaking Hamiltonian belongs to the (3, $3^{*}$) ⊕ ($3^{*}$, 3) representation of SU(3)¯SU(3). It turns out that the rate is anomalously small and indicates that the pure (3, $3^{*}$) ⊕ ($3^{*}$, 3) symmetry breaking is unlikely.

A study of the iodine $L$ x-ray spectra arising from collisions of 15-60-MeV ${}_{}{}^{127}{}_{}{}^{}\mathrm{I}$ ions with target atoms ranging from carbon to lead ($Z_2=6\mathrm{} \mathrm{to} 82$) shows large systematic variations in the relative number of vacancies produced in the $2p_{\frac{3}{2}}$ and the $2p_{\frac{1}{2}}$ subshells.

An accurate spectroscopic measurement has yielded 320.2926 ± 0.0010 Å for the wavelength of the $1s2p{}_{}{}^3{}_{}{}^{}P_{}^{\circ }{}_{}{}^{}-2p^2{}_{}{}^3{}_{}{}^{}P$ transition in ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ I. Combining this wavelength with the well-known position of the $1s2p$ term gives an experimental value of 481 301.5 ± 1.2 ${\mathrm{cm}}^{-1\mathrm{}}$ for the position of the doubly excited $2p^2{}_{}{}^3{}_{}{}^{}P$ term relative to the ground $1s^2{}_{}{}^1{}_{}{}^{}S$. The new measurement is in excellent agreement with Aashamar's theoretical calculation of 481 301.6 ${\mathrm{cm}}^{-1\mathrm{}}$ for the energy of the term.

In a beam-foil experiment, we have observed zero-field oscillations of approximately 25% in the intensity of ${\mathrm{H}}_{\beta }$ radiation polarized parallel to the beam. An unmodulated decay is observed when a signal proportional to the total intensity is examined. Our observations substantiate Macek's theory of coherent decay from fine-structure levels.

A new optical method to detect conduction-electron spin resonance in semiconductors is described. Its main interest is its application to undoped samples in which the properties of free carriers are not perturbed by shallow donor impurities. The $g$ factor of ${10}^8$ photocreated electrons at the bottom of the conduction band in $p$-type GaSb was measured to be $\left|g^{*}\right|=9.3\mathrm{}\pm 0.3$. It is different from most of the previous experimental determinations and from the theoretical prediction $g_{\mathrm{th}}^{}{}_{}{}^{*}=-6.66\mathrm{}$.

The nonlinear interaction of $N$ oscillators, with $N$ not too small ($N\sim 10$), is treated statistically. A diffusion equation for the probability density in action space describes its evolution to a microcanonical distribution over the portion of the energy hyperplane for which the resonance widths (or relative-phase diffusivities) are nonvanishing. These widths are determined in terms of the resonance frequency mismatches and the nonlinear interaction coefficients by nonlinear coupled equations. For diffusion to occur, the interaction strengths must exceed the mismatches.

Phase transitions of the nematic liquid crystal $p$-methoxy-benzylidine, $p-n$ butyl-aniline were studied by recording the low-frequency Raman spectrum. The intensity of the lattice Raman bands undergoes abrupt change at the crystalline-to-nematic phase transition temperature, with an indication of a hysteresis. The band totally disappears at the isotropic (liquid) phase.

It is shown that the correct lowest-order two-particle correlation function solution to the Bogoliubov-Born-Green-Kirkwood-Yvon hierarchy is given via a Green's function whose Fourier transform satisfies the analyticity requirements for causality. The Bogoliubov adiabatic approximation is shown to imply a solution which is acausal. Extension to the $s$-particle correlation function is discussed.

We have confirmed the existence of a new negative carrier of high mobility in superfluid helium, reported by Doake and Gribbon, and determined its zero-field mobility. We suggest that it may be the negative helium ion in a small cavity in the liquid. A series of carriers with mobilities between that of the "fast" and the "normal" (electron bubble) carrier is also shown to exist.

We report experiments in which small helical magnetic fields are added to the basic confinement field of a 3-m-long θ pinch. A combination of these fields having $l=1\mathrm{}$ and $l=0\mathrm{}$ symmetries produces a transverse body force on the plasma column. The strength of the body force has been measured by studying the plasma dynamics and is found to be in agreement with the theoretical value.

Magnetoionic theory predicts that positive Faraday rotation, i.e., the direction without collisions, decreases to zero near $\frac{\nu }{\omega }=1\mathrm{}$ and becomes negative for $\frac{\nu }{\omega }>1\mathrm{}$. Using a 35-GHz microwave beam propagating parallel to the magnetic field and the precursor plasma from an exploding wire, rotation of an initially plane wave is measured throughout the region $\frac{\nu }{\omega }\lessgtr 1$. The negative Faraday effect, as well as the crossover from positive to negative with increasing collisions, is qualitively verified.

The thermodynamic pressure $P_{\mathrm{V}}\mathrm{}(T,H)\mathrm{}$ has been measured in solid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ in the presence of high magnetic fields. Modification of nuclear-spin ordering by the field is observed, indicating antiferromagnetic behavior. The results indicate that the behavior is not quantitatively as expected from the Heisenberg model. A depression of the melting curve in a field has also been observed.

In numerical calculations, we observe a dichotomy in the time evolution of solutions of the high-Reynolds-number, two-dimensional, incompressible Navier-Stokes equations using power-law initial modal energy spectra $E(\kappa ,0)\sim {\kappa }^{-{\mu }_0}$. The boundary is expressed in terms of critical values of viscosity ${\nu }_{\mathrm{cr}}$ and microscale ${\lambda }_{\mathrm{cr}}$. For both parameters initially above critical, $\mu$ approaches 4. For both parameters initially below critical, $\mu$ approaches 1 at large $\kappa$, consistent with equipartition of the vorticity spectrum. In the former case, large-scale vortex states form after a long time; and, in both cases, energy flows to the lowest wave numbers.

Plasma diffusion due to static, nonaxisymmetric perturbations of magnetic or electric field is analyzed in the low collision-frequency region. The diffusion coefficient is found to be proportional to the fraction of the particles with slow drift, and can significantly exceed classical diffusion.

Molybdenum disulfide has been intercalated with sodium and potassium. Both natural crystals of molybdenite and synthetic crystals were used, and measurements made on the intercalated products indicate a superconducting transition temperature of ∼1.3°K for sodium and ∼4.5°K for potassium.

An exactly solvable model is formulated for the electronically induced crystallographic transition. The model contains the essential and new feature that the distortion is conceived to be an operator. This entails a better understanding of the processes involved in this type of transition.

Neutron diffraction measurements on single crystals of ${}_{}{}^{160}{}_{}{}^{}\mathrm{Gd}$ have been performed which allow the reconstruction, by Fourier synthesis, of the magnetization as a function of position. It is shown that the total magnetic moment density can be separated in a logical manner into a local part and a diffuse part. It is suggested that the local part corresponds to the $4f$ polarization and the diffuse part to the conduction-electron polarization. Contour maps show the diffuse contribution to be long range and oscillatory.

The "phonon fluorescence" spectrum of superconducting Sn and ${\mathrm{Pb}}_{0.5}$${\mathrm{Tl}}_{0.5}$ films pumped by a heat pulse is studied through the observation of resonance absorption by Sb donor levels in uniaxially compressed Ge. The spectrum consists primarily of a narrow band of phonons centered about the energy gap $2\Delta$ (1.2 meV for Sn, 1.7 meV for ${\mathrm{Pb}}_{0.5}$${\mathrm{Tl}}_{0.5}$). The power generated in this narrow band is at least hundreds of milliwatts. In the case of Sn the phonon energy has been tuned from 1.2 meV down to 0.7 meV by a magnetic field parallel to the plane of the film.

Far-infrared vibrational modes in vitreous ${\mathrm{As}}_2$${\mathrm{Se}}_3$ and ${\mathrm{Tl}}_2$Se·${\mathrm{As}}_2$${\mathrm{Te}}_3$ have been observed above the glass transition temperatures ($T_g$) and are an indication of the preservation of local order in the liquid phase. In ${\mathrm{As}}_2$${\mathrm{Se}}_3$ these modes exist above the melting point of the crystalline material. At a well-defined temperature $T_s=480\mathrm{}$ K ($>T_g$) the vibrational modes disappear in ${\mathrm{Tl}}_2$Se·${\mathrm{As}}_2$${\mathrm{Te}}_3$. Similar behavior is predicted for all layertype semiconducting glasses, and $T_s$ is proposed as a characteristic temperature for an abrupt change of local order in these materials.