A wide structure observed experimentally in the elastic cross section for electron-hydrogen-atom scattering below the $n=2\mathrm{}$ threshold is analyzed using close-coupling calculations. Good agreement with experiment is found for the six-state approximation.

A multiple-scattering model for calculating molecular orbitals has been applied with reasonable success to several elementary diatomic molecules. These results, together with the flexibility and computational simplicity of the model, suggest that it will be a practical new approach to the theoretical electronic structures of complex, polyatomic molecules.

Low-frequency electrostatic waves in a reflex discharge are stabilized by feeding an amplified and phase-shifted probe signal to a pair of plates at the discharge walls. The plates couple electrostatically to the $k_{\parallel }\approx 0$ drift-type modes and stabilize them, giving a modest increase in density. A root-locus diagram is devised to explain the observed features of the system response.

The Rys F model of hydrogen-bonded antiferroelectrics is generalized to include all ionized vertices. For a class of realistic choices of energy parameters, it is shown that this model is equivalent to a two-dimensional Ising model and consequently exhibits a logarithmically second-order phase transition.

The surface-sheath nucleation field $H_{c3\mathrm{}}$ in Pb-0.25% Bi alloy, a clean strong-coupling type-I superconductor, has been measured from 1.7°K to near $T_c$ (7.2°K). The data allowed a direct determination of the slope ${\left(\frac{d{H}_{c3\mathrm{}}}{\mathrm{dT}}\right)}_{T_c}$ which, along with the temperature dependence of $H_{c3\mathrm{}}$ near $T_c$, is compared with results predicted by recent theories

Both the clean and cesiated (¯1¯1¯1) surfaces of $n$- and $p$-type GaP show very large shifts of work function upon cooling when the surface is illuminated with 1.7-eV light: $\Phi$ increases for $p$-type and decreases for $n$-type material. This is attributed to reduction of surface charge by photoexcitation of electrons into or out of surface states. The surface-state density is ∼4 × ${10}^{12}$ ${\mathrm{cm}}^{-2\mathrm{}}$ and is unaffected by submonolayer quantities of Cs.

We study the effects of a sudden change in the external magnetic field on the propagation of magnon states.

The main conclusions of a theoretical investigation of magnon-interaction effects in $\alpha -{\mathrm{Fe}}_2{\mathrm{O}}_3$ are briefly reported. It is shown that the optic modes can have very low energy and it is suggested that these modes may play an important role in the mechanism of the Morin phase transition.

The systematic inclusion of inelastic effects in low-energy electron diffraction leads to (1) broad (10- to 20-eV) peak widths, (2) asymmetric peak shapes, and (3) low reflectivities. A connection between the "dynamical" and "kinematic" approaches to diffraction theory is developed.

We argue that the observed attraction in $\pi$-nuclear interactions for $l\ne 0$ should become a repulsion for large nuclear radius. The critical radius depends on angular momentum.

${\mathrm{Nd}}^{139m}$ in its $\epsilon$ decay preferentially populates a multiplet of six high-lying, high-spin, odd-parity states in ${\mathrm{Pr}}^{139}$. We interpret this as ${\left(\pi d_{\frac{5}{2}}\right)}^2{\left(\nu d_{\frac{3}{2}}\right)}^{-2\mathrm{}}{\left(\nu h_{\frac{11}{2}}\right)}^{-1\mathrm{}}\to \left(\pi d_{\frac{5}{2}}\right){\left(\nu d_{\frac{3}{2}}\right)}^{-1\mathrm{}}\times {\left(\nu h_{\frac{11}{2}}\right)}^{-1\mathrm{}}$, with the ${\mathrm{Pr}}^{139}$ states being three-quasiparticle states.

It is shown that a phenomenological approach to the four-particle, four-hole band in ${\mathrm{O}}^{16}$ gives reliable predictions for the level spacings and the electromagnetic transition probabilities.

A new approach to equations of motion in general relativity is presented, in which matter is treated as singularities, of a particular kind, in the Weyl tensor. The motion of these singularities is defined in terms of their own surrounding space. The equations of motion then follow uniquely from the Einstein field equations. A concomitant result is the existence of internal structure for the singularities and equations of motion for this structure.

Meteoritic whitlockite containing excess fission tracks has a large concentration of excess neutron-rich xenon isotopes which is 25 times that calculated from the track density. The isotopic spectrum is identical to that calculated previously for the Pasamonte achondrite. These results uniquely associate this spectrum with in situ fission. Identification of the fissioning nucleus as ${\mathrm{Pu}}^{244}$ gives ${\mathrm{Pu}}^{244}$/${\mathrm{U}}^{238}$ ≅ 1/30 at the time of xenon retention. Neither "sudden" nor "uniform" nucleosynthetic models give consistent solutions for ${\mathrm{Pu}}^{244}$/${\mathrm{U}}^{238}$ and ${\mathrm{U}}^{235}$/${\mathrm{U}}^{238}$.

An experimental investigation of transient electromagnetic wave propagation in the microwave frequency range related to the theoretical investigation of Sommerfeld and Brillouin is reported. Both the Sommerfeld and Brillouin precursors are shown experimentally.

In ${\pi }^{+}d$ interactions at 2.7 GeV/c we have observed the $D^0$ meson with mass 1.27 ± 0.01 GeV/${\mathit{c}}^2$ and width 30 ± 15 MeV/${\mathit{c}}^2$ to decay into the ${\delta }^{\pm }$ meson with mass 0.98 ± 0.01 GeV/${\mathit{c}}^2$ and width 40 ± 15 MeV/${\mathit{c}}^2$. The ${\delta }^{\pm }$ meson is further observed to decay into ${\pi }^{\pm }\eta$ with both neutral and charged decays of the $\eta$.

The $K\pi \pi$ enhancement at 1780 MeV (the "$L$ meson") is copiously produced in our $K^{+}p$ experiment at 12 GeV/c. We show that this "meson" can be explained as a threshold enhancement in the $K_N\mathrm{}\left(1420\right)\mathrm{}\pi$ system. We see no evidence for this enhancement in channels other than $K_N\mathrm{}\left(1420\right)\mathrm{}\pi$.

The rate of the $\mathrm{CP}$-nonconserving decay $K_L^{}{}_{}{}^0\to 2{\pi }^0$ has been measured relative to that of $K_L^{}{}_{}{}^0\to 3{\pi }^0$ using a monoenergetic $K$ beam and a nearly $4\pi$ solid-angle detector system employing lead-plate spark chambers and shower counters. The measured branching ratio 1.31% ± 0.18% (statistical) ±25% (systematic) leads to a value for the $\mathrm{CP}$-nonconservation parameter ${\left|{\eta }_{00}\right|}^2$ of (14.1 ±3.4) × ${10}^{-6\mathrm{}}$.

It is shown that the Veneziano model can be cast into a form in which the leading asymptotic behavior at high energy in the direct channel comes from a term containing no direct-channel resonances. The question of the meaning of duality under such circumstances is raised and discussed briefly.

A selection rule for $p$-wave amplitudes of nonleptonic hyperon decays is derived from the duality principle. It predicts $P\left(\Sigma _{-}^{}{}_{}{}^{-}\right)=0\mathrm{}$ and $P({\Omega }^{-}\to {\Xi }_{\pi })=0\mathrm{}$.