When nuclear spin-lattice relaxation in solids is due to rapid random rotation of methyl groups, the Zeeman relaxation can be nonexponential. This is because the magnetization is dynamically coupled to the so-called rotational polarization. It is shown that rotating the sample perpendicular to the magnetic field with angular velocity large compared with the relaxation rate decouples these parameters, resulting in an almost exponential Zeeman relaxation close to that predicted by the spin-temperature theory.

Various experiments on the propagation of high-frequency phonons in liquid ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ at $T=0.1\mathrm{}$ K lead to the conclusion that there is a critical wave vector $q_c$ such that phonons with wave vector $q<\mathrm{}{q}_c$ have very short mean paths while those with $q>\mathrm{}{q}_c$ have very long ones. As $q_c$ is adjustable over a wide range we recognize the possibility for phonon spectroscopy, using the helium as a tuneable high-pass phonon filter.

I have observed level differences between two baths of superfluid helium which are multiply connected by two orifices whenever the flow velocity past the orifices was of such value as to cause the quantum-mechanical phase difference between them to be an odd multiple of $\pi$.

The hydrodynamic theory of mass transport in $A$-${}_{}{}^3{}_{}{}^{}\mathrm{He}$ is derived from that phase's broken symmetries and thermodynamics. First, second, and fourth sound as well as orbit waves are obtained as the normal modes.

We report on the stability of plane Langmuir solitons to perturbations in the transverse direction and of cylindrically symmetric solitons to azimuthal perturbations. Two-dimensional numerical solutions of the basic equations, including the effect of finite ion inertia, show that both cases are unstable and that the collapse of annular solitons in the azimuthal direction is faster than their radial collapse.

A source of polarized ${}_{}{}^3{}_{}{}^{}\mathrm{He}_{}^{++}{}_{}{}^{}$ particles based on the Lamb shift in ${}_{}{}^3{}_{}{}^{}\mathrm{He}_{}^{+}{}_{}{}^{}$ ions is now operating. After axial injection into a cyclotron and acceleration to 33 MeV the on-target beam intensity in a scattering chamber exceeds 0.1 nA. Nuclear scattering experiments together with a study of the source characteristics indicate a beam polarization value of $P=0.40\mathrm{}\pm 0.05$.

We present results of measurements of the total cross section for neutrons on a variety of nuclei in the momentum range 30 to 270 GeV/c. The measurements were made with the standard transmission technique and have a typical accuracy ∼1%. The cross sections are compared with theoretical predictions. It is found that a correction for inelastic screening in the nucleus is required. The cross sections are found to vary as $A^{0.77}$ over the entire energy range.

Charged-pion rapidity correlations are compared and found to have a similar peaked structure when studied inclusively. However, when the same data are studied semi-inclusively no correlation is found for like-charged pions and for unlike-charged pions in the central region. Inclusive correlations in these cases appear then from the convolution of the uncorrelated spectra at each multiplicity and the multiplicity distribution. Correlation in ${\pi }^{+}{\pi }^{-}$ is observed at small $\Delta y$ only for $y$ large.

Seven examples of strange-particle production by neutrinos are observed in the 12-ft bubble chamber. One event represents the first observation of associated production by the weak neutral current.

The coherent process ${\pi }^{-}+A\to A+{\pi }^{-}+{\pi }^0$ has been measured using nuclear targets. Sharp peaks are observed in the $t^{\prime }$ distributions. The $\pi \pi$ mass spectrum is dominated by the ${\rho }^{-}$ meson produced in the nuclear Coulomb field and by ${\omega }^0$ exchange in the nuclear surface. The Coulombic process yields a measurement of the radiative width, $\Gamma ({\rho }^{-}\to {\pi }^{-}+\gamma )=35\mathrm{}\pm 10$ keV, which is in poor agreement with the simple unbroken-SU(3) prediction of 100 keV.

We have observed a second sharp peak in the cross section for $e^{+}{e}^{-}\to \mathrm{hadrons}$ at a center-of-mass energy of 3.695±0.004 GeV. The upper limit of the full width at half-maximum is 2.7 MeV.

The branching ratio for the decay $\pi \to e\nu \gamma$ has been measured in a counter experiment in which the $e^{+}$ was detected in a magnetic spectrometer and the $\gamma$ ray in a lead-glass hodoscope. From the measured branching ratio we determine $\gamma$, the ratio of the axial-vector form factor to the vector form factor. The latter is computed by using conserved-vector-current theory and ${\tau }_{{\pi }^0}$, the ${\pi }^0$ lifetime. Adopting a best value 0.86×${10}^{-16\mathrm{}}$ sec, we obtain $\gamma =0.15\mathrm{}\pm 0.11$ or $\gamma =-2.07\mathrm{}\pm 0.11$. A comparison between the measured values of $\gamma$ and various theories is made.

A Dalitz plot of 509 000 ${K_L}^0\to {\pi }^{+}{\pi }^{-}{\pi }^0$ decays is analyzed, using ${\mathrm{}\left|M\right|\mathrm{}}^2\propto 1+aY+b{Y}^2+cX+d{X}^2+\dots$, where $X$ and $Y$ are the Dalitz variables. We find no measurable $X$ dependence; we do find that a significant $X^2$ and $Y^2$ dependence is present. In addition, the spectrum cannot be fit with a matrix element linear in $Y$. Our best fit yields $a=-0.917\mathrm{}\pm 0.013$, $b=0.149\mathrm{}\pm 0.013$, and $\alpha =0.055\mathrm{}\pm 0.010$. Comparison with $\tau$ decay indicates a definite $\left|\Delta I\right|=\frac{1}{2}$ violation in the nonsymmetric amplitudes.

The time dependences of uv emissions from dense argon and xenon are monitored following low-intensity electron excitation. The uv transitions originate on the lowest $0_{\mathrm{u}}^{+}$ and $1_{\mathrm{u}}$ molecular states. For argon the radiative lifetimes are 3.2±0.3 μsec ($1_{\mathrm{u}}$) and 4.20±0.13 nsec ($0_{\mathrm{u}}^{+}$), while for xenon they are 96±5 and 5.5±1.0 nsec. The radiating molecules are formed by three-body destruction of excited atoms; the rate coefficient for argon is (2.8±0.3) × ${10}^{-33\mathrm{}}$ ${\mathrm{cm}}^6$/sec.

We studied the fluorescence spectrum of $E\to B$ transitions in molecular iodine following two-photon absorption. Discrete re-emission lines terminating in $B$-state levels ranging from $v=0\mathrm{}$ to the dissociation limit were observed in addition to a series of broad diffuse lines. These diffuse lines represent the first observation of Condon "internal diffraction" resulting from a single vibronic state, and therefore the variation of the bands directly displays the variation of the Franck-Condon factor.

The line shape of the electron energy-loss spectra due to $3p\to 3d$ excitation is reported for Ni. The observation is interpreted by a Fano-type interaction in which the excited configuration decays by Coster-Kronig processes into the continuum of excitations of the $3d$ band. These processes appear to hold generally for the transition metals in both electron scattering and soft-x-ray absorption.

Observed Doppler shifts of neutral-hydrogen ${\mathrm{H}}_{\alpha }$ radiation in the poloidal and toroidal directions in the Oak Ridge tokamak experiment are shown to be consistent with neoclassical theory. The inferred shift and distortion of the proton distribution function in the banana-plateau regime is caused by the radial pressure gradient and by the ambipolar electric field, whose steady-state value is determined by nonambipolar diffusion due to charge exchange.

A microscopic theory of ionic transport in superionic conductors is presented. Based on a liquidlike description of the ionic carriers, it describes the frequency and temperature dependences of the conductivity. A sum rule is obtained and the theory predicts the existence of a conductivity peak which scales with the inverse of the ionic carrier mass. The results are in good agreement with recent data on Na and Ag $\beta$-aluminas.

The critical dynamics of a model isotropic ferromagnet is studied in $6-\epsilon$ dimensions both above and below $T_c$. The renormalization group and the characteristic frequency exponent $z$ are determined to order $\epsilon$. Implications of the renormalization group are discussed. A direct calculation of the dynamic response function to order $\epsilon$ shows many interesting features, especially for $T<\mathrm{}{T}_c$.

The positions and widths of $E0\mathrm{}$, $E1\mathrm{}$, $E2\mathrm{}$, $E3\mathrm{}$, and $E4\mathrm{}$ giant resonances are calculated with a density-dependent force.