The intensity of beam-foil-excited $\mathrm{Ly}-\alpha$ radiation has been measured in electric fields alternately parallel and antiparallel to the beam. Measurements were made at three energies—110, 165, and 210 keV—and three field strengths. From these data the $S-P$ co-herence term ${\sigma }_{\mathrm{SP}}$ has been determined. The magnitude of ${\sigma }_{\mathrm{SP}}$ is found to be 0.07 at 110 keV, 0.19 at 160 keV, and 0.22 at 210 keV. These results establish that beam-foil-excited hydrogen atoms have a nonzero electric dipole moment.

We have observed ESR signals of negative ions in liquid helium. The linewidth and $g$ value have been measured. Electrons injected into helium by field emission from ferromagnetic tips are shown to be polarized. We propose a new technique for the measurement of electron spin polarization.

The current induced in a toroidally confined hot-electron plasma is observed to be carried by energetic electrons, in quantitative agreement with a classical acceleration model, and to decay by collisions, free of significant anomalous effects.

We present molecular-dynamics computations of the velocity autocorrelation function and the dynamical structure factor of the classical one-component plasma. At high densities, the former exhibits marked oscillations, whereas the latter consists of very sharp peaks near the plasma frequency, up to wave vectors of order $\frac{1}{a}$, where $a$ is the ion-sphere radius. The resulting dispersion curve is discussed.

We present the first direct spectroscopic study of electrons bound in image-potential-induced surface states outside liquid helium. We have observed absorption lines which show the expected linear Stark effect in the presence of an electric field. Zero-field splittings extrapolated from the data are 125.9 and 148.6 GHz for electronic transitions from the ground state to the first two excited states in the image-potential well.

The system C${\mathrm{S}}_2$ + C${\mathrm{H}}_3$N${\mathrm{O}}_2$ shows $\beta =0.315\mathrm{}\pm 0.004$ over ${10}^{-6\mathrm{}}<\epsilon =\frac{|T-T_c|}{T_c}<2\mathrm{}\times {10}^{-1\mathrm{}}$ with no indication of a classical value ½ even far away from $T_c$. The diameter shows a curvature and is of the form ${\varphi }_c+b\epsilon +f{\epsilon }^{\frac{7}{8}}\exp (-g{\epsilon }^h)$.

A simple argument demonstrates that one should expect polar and nonpolar fluids to have the same critical exponents.

A mechanism is given for the generation of a transverse electromagnetic wave by a finite-amplitude Langmuir wave of lower frequency. The relationship of this effect to the oscillating two-stream instability is indicated and the conditions for its observation experimentally are discussed.

The superconducting phase transition is predicted to be weakly first order, because of effects of the intrinsic fluctuating magnetic field, according to a Wilson-Fisher $\epsilon$-expansion analysis, as well as a generalized mean-field calculation appropriate to a type-I superconductor. Similar results hold for the phase transition from a smectic-$A$ to a nematic liquid crystal.

For a number of liquid sodium-cesium alloys the electrical resistivity $\rho$ has been measured as a function of temperature $T$ in the range 50-300°C. As a function of the cesium concentration $c$, ${\left(\frac{\partial \rho }{\partial T}\right)}_p$ exhibits a distinct minimum for $c=0.6\mathrm{}$, which gradually disappears at higher temperatures. This minimum is related to the results for the resistivity at high pressure recently obtained by Tamaki, Ross, Cusack, and Endo.

The inhomogeneous-electron-gas theory of Hohenberg, Kohn, and Sham has been used to investigate the effects of nonlocal exchange and correlation on the Fermi surface of a simple cubic metal. The periodic lattice effects were represented by a realistic simple model pseudopotential. We find that the nonlocal terms substantially reduce the maximum Fermi-surface distortions, as experiments suggest.

On the basis of x-ray monodomain and powder patterns, the structure of new identified terephthal-bis-butylaniline phases is described. These phases present a relatively high degree of order and appear as intermediate states between the smectic mesophases and the crystalline state.

An exact calculation of the acoustic-phonon-assisted jump rate has been carried out. It is found that while the Miller-Abrahams (single-phonon) approximation is adequate for the study of shallow-impurity conduction at helium temperatures, it is typically inappropriate for the study of hopping between deep states in noncrystalline solids. In particular, the multiphonon jump rate will display a nonactivated temperature dependence below the Debye temperature which is similar to the often-seen $\exp [-{\left(\frac{T_0}{T}\right)}^{\frac{1}{4}}]$ behavior.

A simple explanation is presented for the observed tendency of the spin-orbit part of the optical potential for a proton scattered by a nonspherical target nucleus to be more deformed than the central part. The explanation is based on the fact that the range of the central two-body force is longer than that of the two-body spin-orbit force.

We have examined the difference between polarization and analyzing power for the reaction ${}_{}{}^3{}_{}{}^{}\mathrm{H}\mathrm{}(p,n)\mathrm{}{}_{}{}^3{}_{}{}^{}\mathrm{He}$. We find that this difference is due to the presence of ${}_{}{}^3{}_{}{}^{}P_2^{}{}_{}{}^{}\leftrightarrow {}_{}{}^3{}_{}{}^{}F_2^{}{}_{}{}^{}$ transitions which are enhanced in the vicinity of the lowest $2^{-}$ state of ${}_{}{}^4{}_{}{}^{}\mathrm{He}$.

We have measured $\beta -\alpha$ angular correlations in $A=8\mathrm{}$ in order to extract a value for the weak-magnetism element as part of a test of conservation of vector current. Possible contributions to the angular correlation from vector second-forbidden matrix elements and a second-class induced-tensor matrix element are shown to be small on the basis of experimental evidence and wave-function calculations.

An $E2\mathrm{}$ or $M1\mathrm{}$ resonance is observed in the reaction ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}(p,{\gamma }_0{\gamma }_1{\gamma }_2){}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}$ at $E_p\simeq 20.0$ MeV ($E_x\simeq 23.7$ MeV) with a width $\Gamma \sim 3.5$ MeV. Present evidence supports its identification as a collective $E2\mathrm{}$ excitation.

We show that the tensor polarization in elastic electron-deuteron scattering at large but presently attainable momentum transfers is supersensitive to the deuteron wave function within 0.5 fm, but insensitive to the percentage of $D$ state assumed. This may give the first practical method to learn something directly about the two-nucleon interaction in the core.

On the basis of Einstein's theory of relativity, the principle of causality, and Le Chatelier's principle, it is here established that the maximum mass of the equilibrium configuration of a neutron star cannot be larger than $3.2M_{\mathrm{}[m?]\mathrm{}}$. The extremal principle given here applies as well when the equation of state of matter is unknown in a limited range of densities. The absolute maximum mass of a neutron star provides a decisive method of observationally distinguishing neutron stars from black holes.

We report measurements of the charged-hadron multiplicity for electrons scattered by protons at momentum transfers up to $Q^2=8\mathrm{}$ ${\mathrm{GeV}}^2$, and for $s$ up to 14 ${\mathrm{GeV}}^2$. The multiplicity is consistent with a simple lns behavior, with little or no $Q^2$ dependence above $Q^2=1.4\mathrm{}$ ${\mathrm{GeV}}^2$.