We report differential cross sections for ${\rho }^{-}$ production near 180° in the reaction ${\pi }^{-}p\to p{\rho }^{-}$ at 8 and 16 GeV/c. These cross sections, which cover a range of $\mathrm{}\left|u\right|\mathrm{}<~0.6$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$, are well represented by the formula $\frac{d\sigma }{\mathrm{du}}=A\exp \mathrm{}\left(\mathrm{Bu}\right)\mathrm{}$ and are comparable in magnitude to backward ${\pi }^{-}p$ elastic cross sections. Results are compared to Regge model calculations.

${\rho }^{-}$ production near backward direction has been analyzed in a Regge-pole model with the emphasis on kinematic structures and constraint relations. We obtain results which agree well with experimental data and are consistent with backward elastic scattering.

The asymmetry generated by the interference between the $\eta$ and nonresonant background $3\pi$ amplitudes has been calculated for previously reported data in the decay $\eta \to {\pi }^{+}{\pi }^{-}{\pi }^0$. An upper limit of 0.23% has been found for the effect in this sample of data.

We show that the current-algebra predictions of Weinberg for $\pi -\pi$ scattering may be consistent with the sum rules proposed by Chu and Desai, who have claimed otherwise. We demonstrate that high-spin resonances neglected by Chu and Desai can make substantial contributions to the sum rules, and that inclusion of the next resonance after those used by Chu and Desai results in agreement between Weinberg's predictions and the sum rules. It is possible and likely that the remaining high-spin resonances give negligible net contribution.

The residue of the $P^{\prime }$ trajectory has been obtained from experimental data and found to be in agreement with the Ansatz of Barger and Phillips.

The significance of new ${\pi }^{\pm }p$ polarization data for Regge exchange models is extracted and correlated with dips and bumps in recent $\frac{d\sigma }{\mathrm{dt}}$ measurements. A semiquantitative description of the data through the entire region $0<-t<\mathrm{}4\mathrm{}$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$ is presented. As a byproduct, we extrapolate the ${\pi }^{\pm }p$ polarization and ${\pi }^{-}p\to {\pi }^{0}n$ differential cross section into the region $-t>\mathrm{}2\mathrm{}$, where there are no data yet.

Ionizing collisions of 114- and 50-eV electrons with helium have been studied by the measurement of the two outgoing electrons in coincidence as a function of the angle between them. At the same time the energies of the two electrons are determined. The results are compared with solutions of the Lippmann-Schwinger equation. Angular correlation distributions are found to be more sensitive for the test of a theory than energy loss and differential cross sections or the total cross section.

Two-component cholesteric liquid crystal films have been observed to exhibit a remarkable structural dependence on composition. There is evidence that the relationship of color and temperature in these films is connected with this dependence.

The absorption of light by free continuum polarons is treated in the framework of the Landau-Pekar approach which for this problem is not restricted to strong coupling but gives at least the qualitative behavior for intermediate coupling ($\alpha \approx 3 \mathrm{to} 6$). The absorption curve consists of a relatively narrow zero-phonon peak and a broad sideband showing a multiphonon structure. The zero- and one-phonon contributions and the lowenergy part of the two-phonon contribution have been evaluated numerically.

We argue that the structure of ${\mathrm{O}}^{16}$ cannot be completely understood unless the position of the first $0^{+}$ state can be calculated without using adjustable parameters. We further demonstrate that this state cannot be calculated by Hartree-Fock or related methods using the present generation of nuclear forces.

We have studied the formation of ${\mathrm{O}}^{-}$ ions with zero kinetic energy from C${\mathrm{O}}_2$, a reaction typical of the forms $e^{-}+XYZ\to X^{-}+YZ or \to X{Y}^{-}+Z$, where $\mathrm{XYZ}$ is a triatomic molecule. We find that the onset energy shows a marked dependence on the temperature of the gas, and we conclude that such onset measurements must be extrapolated to 0°K to give meaningful electron affinities.

We propose an explanation for different types of fluctuations observed in multipole experiments based on a new formal solution of the general integral equation that yields, besides the known hydromagnetic mode types, modes with frequency smaller than the average ion slow-excursion frequency. The relevant modes are of flute type, have frequency range and phase velocity in agreement with observation, and become almost purely growing and unlikely to be observed as fluctuations in conditions where these have not been detected.

Measurements of supercritical heat flow in He II are consistent with a mutal friction constant which diverges near $T_{\lambda }$. They also explain the apparent depression of $T_{\lambda }$ observed by Erben and Pobell, and the "critical heat flux" near $T_{\lambda }$ reported by Bhagat and Winer.

A high-temperature (∼70-1200°C) resistivity recovery study of fast-neutron-irradiated ($E_n>~1$ MeV) molybdenum shows an anomalous saturation effect above about (5-10) × ${10}^{19}$ n/${\mathrm{cm}}^2$. This effect is interpreted as resulting from the self-annealing of the stage-III defects at the higher fluences (∼${10}^{21}$ n/${\mathrm{cm}}^2$) leaving essentially only the stage-IV defects after reactor ambient irradiation.

The coherent excitation of polaritons has been achieved in the III-V semiconductor GaP for the first time by a nonlinear, optical parametric process. We are able to describe the polariton dispersion curve in the $\omega -k$ space and to measure the absorption coefficient of the crystal near the Reststrahl band. The results are discussed on the basis of recent theories on the polariton disperson and damping in GaP.

The $\gamma -\gamma$ directional correlation of the 692-123 keV, $2^{+}$′ → $2^{+}$ → $0^{+}$ cascade in ${}_{}{}^{154}{}_{}{}^{}\mathrm{Gd}$ was remeasured with an improved Ge(Li)-NaI system. The spectra in coincidence with the Compton background and the 123-keV photopeak were simultaneously recorded at each angle. The new results averaged with our earlier work yield $A_2=-0.141\mathrm{}\pm 0.022$ and $A_4=0.311\mathrm{}\pm 0.040$. These values are consistent only with the 692-keV transition being essentially pure $E2\mathrm{}$.

A reanalysis of inelastic electron-scattering measurements from giant $M1\mathrm{}$ states in ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ and ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ and in ${}_{}{}^{26}{}_{}{}^{}\mathrm{Mg}$ is made using Coulomb-distortion corrections in place of the plane-wave Born-approximation analysis. It is shown that the corrections even for light nuclei can reduce the nuclear form factors for $M1\mathrm{}$ transitions outside the experimental error quoted in the plane-wave Born approximation analysis of electron scattering. This reduction in $B(M1, q)$ is magnified at the photon point.

The energy spectrum and asymmetry of neutrons emitted directly on the capture of polarized muons by ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ have been calculated in a simple nuclear shell model, taking account of terms proportional to the nucleon momentum. The energy spectrum is within the error brackets of recent experiments with the nucleon-momentum terms making a small contribution. The asymmetry coefficient is strongly affected by the inclusion of the momentum-dependent terms and is found to change sign and increase in magnitude with increasing energy, in qualitative agreement with recent experiments.

The neutron-hole, proton-hole states of ${\mathrm{Tl}}^{206}$ have been studied by the direct reaction ${\mathrm{Pb}}^{208}(d, \alpha ){\mathrm{Tl}}^{206}$ with 17-MeV deuterons. The experimental resolution of 15 keV or better permitted the detection of many two-hole states, most of them previously unknown. For most levels $L$ values could be extracted from the comparison of microscopic distorted-wave Born approximation (DWBA) calculations with experimental angular distributions. The experimental level energies and $J^{\pi }$ assignments (or limits) are compared with recent calculations by Kuo and are found to be in good agreement.

Evidence is presented confirming the existence of the $\Xi \mathrm{}\left(1815\right)\mathrm{}$ baryon with strangeness $S=-2\mathrm{}$ as well as two new $\Xi$ resonances with masses 2030±10 MeV and 2430±20 MeV, respectively. It is speculated that the $\Xi \mathrm{}\left(2030\right)\mathrm{}$ is a member of a ${\frac{5}{2}}^{+}$ octet, and an SU(3) analysis of the decay rates of the conjectured states is in reasonable agreement with the experimental data.