We present differential cross sections for neutron-proton charge-exchange scattering from 8 to 29 $\frac{\mathrm{GeV}}{c}$. The data, based on ∼ 23 000 events, extend to four-momentum transfers $\mathrm{}\left|u\right|\mathrm{}$ as large as 1.0 ${\left(\frac{\mathrm{GeV}}{c}\right)}^2$. The shape of the differential cross sections and the momentum dependence are examined in detail.

We evaluate the maximum allowed value of the ratio between the total $N$-photon ionization rates for circularly and linearly polarized incident light. It appears that this maximum increases very rapidly with $N$.

We report the scattering of C${\mathrm{O}}_2$-laser light from driven cyclotron-harmonic waves in a collisionless plasma of density 4 × ${10}^{10}$ ${\mathrm{cm}}^{-3\mathrm{}}$. Using light-mixing spectroscopy, we observe scattering from waves with frequencies of several hundred megahertz, wavelengths from 2.0 to 0.75 mm, and associated fractional electron-density modulations as small as ${10}^{-5\mathrm{}}$.

Results on the temperature dependence of orientational order at constant molar volume in the nematic liquid crystal $p$-azoxyanisole are reported for the first time. These results clearly indicate the failure of theories of the nematic phase which do not include both energetic and steric intermolecular interactions.

The interpretation of Osheroff, Richardson, and Lee of their recent measurements of the solidification pressure of ${\mathrm{He}}^3$ is reexamined. On the basis of a different assumption about the thermal coupling in the solid, it is concluded that the transition is unlikely to be of first order and is more likely the expected $\lambda$ transition to the ordered antiferromagnetic phase.

We present experimental evidence to support the nonsingular model for screw disclinations of strength $S=+1\mathrm{}$.

Equilibrium transport coefficients are calculated for a three-dimensional magnetized plasma. It is shown that the transverse spatial diffusion and conductivity coefficients are related via a generalized Einstein relation. These coefficients have both a $\frac{1}{B}$ (volume dependent) term (with $B$ a uniform magnetic field) as well as a $\frac{1}{B^2}$ (volume independent) term for a finite plasma. For an infinite plasma, the coefficients have a "classical" $\frac{1}{B^2}$ dependence.

Dust particles on the wall of a superfluid flow channel provide sites for generation of quantized vorticity at a low critical velocity. The mechanism is thermal nucleation of vortices in a region of large local velocity near the contact between the particle and the wall. The resulting critical velocity is only weakly temperature dependent, or possibly temperature independent, and is consistent in magnitude with experimental critical velocities for a variety of channel sizes and shapes.

A series of structures is observed in the field dependence of the current threshold of a type-II superconductor in a longitudinal magnetic field. In the mixed state the structures appear in the field $H=\frac{H_{c2\mathrm{}}}{N}$ ($H_{c2\mathrm{}}$ is the upper critical field; $N$ is an integer), while for the case $H>\mathrm{}{H}_{c2\mathrm{}}$, they are observed when $H=N^{\frac{1}{2}}{H}_{c2\mathrm{}}$. These phenomena are discussed on the basis of the Ginzburg-Landau equation. The experimental data in the mixed state are interpreted as evidence for the existence of some new quantum states other than the Abrikosov state.

Angular distributions of ions produced in the electron impact ionization of a number of atoms and molecules have been measured for electron energies up to 300 eV. For ${\mathrm{He}}^{+}$ and ${\mathrm{Ar}}^{+}$ the ion distributions are found to mirror the "recoil" electron distributions of Ehrhardt and co-workers, thus confirming their explanation of their recoil peak. General trends in the angular distributions are summarized.

We report here new theoretical values for the $2{}_{}{}^3{}_{}{}^{}P$ fine-structure splittings in helium. Comparison with experiment provides significant confirmation of the newly computed effects.

In view of the recently reported discrepancies between theoretical calculations and accurate experimental measurements of muonic x-ray energies for several elements in the energy range 150-440 keV, we have recalculated the vacuum polarization corrections. Our results reduce, but do not eliminate, the discrepancies. We discuss the effects of a possible anomalous coupling of the muon to a speculative scalar meson of the type suggested by Weinberg.

The EPR of ${\mathrm{Ce}}^{3+}$ has been observed in sites of cubic symmetry for the first time. The unusually large deviation of the observed $g$ values for ${\mathrm{Ce}}^{3+}$ in CaO, SrO, and BaO from the theoretical value calculated for a pure ${\Gamma }_7$ ground state can be attributed mainly to static crystal-field admixtures.

We derive a nonlinear integral equation, which has three-body correlations built in it, for the Fourier transform of the polarization charge around a positron in an electron liquid. The calculated annihilation rate of the positron in the entire metallic density range, besides being in very good agreement with experiment, merges smoothly into the mean positronium lifetime for larger density. To illustrate the large nonlinear effects, the polarization charge around a fixed proton for a density $r_s=2\mathrm{}$ has also been calculated.

An experiment is described which was designed to measure both the lifetime and the mobility of image-potential—bound electrons on liquid helium. No evidence for bound states with a lifetime greater than a few microseconds was observed, in disagreement with the results of two different experiments recently presented by other authors.

The critical density ${\rho }_c$ of Xe has been determined by two independent methods. The first value, 1.1128 ± 0.0003 g/${\mathrm{cm}}^3$, is based on coexistence-curve data and extrapolation to the critical temperature using the "law of rectilinear diameter." The second method, based on critical-isotherm data and an analysis of gravitational effects, reveals no deviation of the diameter from linearity within the limits of error. If ${\rho }_c$ differs from the extrapolated value, the difference is less than 0.5%.

By directly measuring the difference in velocity of 30 and 90 MHz sound waves in liquid ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ below 100 mK, we have determined that the elementary excitation spectrum cannot be described by an expression $\epsilon \mathrm{}\left(k\right)=c\hslash k(1+{\alpha }_{1}k+{\alpha }_2{k}^2+\cdots )$ which has a value for ${\alpha }_1$ that is greater than 0.01 Å.

Three-dimensional ion acoustic turbulence is excited by injecting a cold ion beam into a nonmagnetized plasma with $\frac{T_e}{T_i}>5\mathrm{}$. A rapid, approximately exponential heating of the ion beam is observed along the beam path. The heating rates level off when the ion temperature approaches $0.2T_e$. The turbulent ion acoustic wave energy density does not exceed $\mathrm{}(1-3)\mathrm{}\times {10}^{-3\mathrm{}}{T}_e$. Wave saturation, which occurs before significant dissipation of ion beam energy, is consistent with orbit-diffusion strong-turbulence theory.

A model for He II flow past a Rayleigh disk is presented which assumes that superfluid potential flow and normal fluid Helmholtz flow occur. A torque which increases as the temperature decreases is predicted, agreeing with Pellam's measurements in rotating helium below $T_{\lambda }$. New measurements of the torque on a Rayleigh disk in nonrotating helium are presented, indicating Helmholtz flow above $T_{\lambda }$, a continuous torque at the $\lambda$ point, and increasing torque below $T_{\lambda }$.

The energy, width, and yield of noncharacteristic x-rays are reported from collisions of argon ions at energies from 25 to 200 keV with targets of C, Al, Si, and solid Ar. The x-ray band has a peak at ∼ 1160 eV with a full width at half-maximum of ∼ 700 eV for solid Ar targets and a peak at ∼ 900 eV with a full width at half-maximum of ∼ 300 eV for the other targets. The yield increases with ion energy and decreases with the target $Z$.