Freedman has shown that coherency and the neutral current theory of neutrinos imply a scattering cross section for neutrinos off heavy nuclei proportional to the square of the atomic weight. The collapse of an iron-core star produces a hot neutron star surrounded by a thin iron layer. Because of the large scattering rate in the outer layer, neutrinos from the hot neutron core are able to accelerate the iron layer to above escape velocity.

Evidence is presented for an enhancement in the $\omega \pi \pi$ mass spectrum at the $A_2$ mass region in ${\pi }^{+}p$ interactions at 5 GeV/c. Assuming this effect to be the $A_2$, we calculate the decay rate relative to the $\rho \pi$ decay mode and obtain the results 0.29 ± 0.08 and 0.10 ± 0.04 for the two final states $A_2^{}{}_{}{}^0{\Delta }^{++}$ and $A_2^{}{}_{}{}^{+}p$, respectively. Possible explanations of the discrepancy between these numbers are suggested.

An enhancement near the $\omega p$ threshold has been observed with a mass of 1820 MeV and a width of about 120 MeV from the reaction ${\pi }^{-}p\to {\pi }^{-}\omega p$ at 4.5, 6, and 14 GeV/c. There is no strong evidence for $\pi N$ or $\rho N$ decay modes. We examine spin and parity and production characteristics.

We describe an experimental search for particles with fractional charge (quarks) with mass below 11 GeV/${\mathit{c}}^2$ produced by proton-nucleus collisions at 200 and 300 GeV. No evidence for such particles was found. Limits on the quark production cross section are given.

The multiplicity and inclusive single-particle distribution for $e^{+}+e^{-}\to \pi +X$ are calculated for Landau's hydrodynamic model. At 3 and 5 GeV the collective motion is less important than the thermal motion. The average pion energy obtained in the Stanford linear-accelerator colliding-beam experiment is consistent with either an ultrarelativistic equation of state or one based on the observed hadron spectrum.

We have measured the polarization state of the light emitted in the ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ I, $2s{}_{}{}^1{}_{}{}^{}S-3p{}_{}{}^1{}_{}{}^{}P$ transition after excitation in a beam-foil experiment and find a partial elliptical polarization which depends upon the tilt angle of the carbon foil relative to the beam axis. This indicates that the emergent beam is oriented as well as aligned as a result of an interaction at the foil surface. The relative excitation cross sections and off-diagonal density-matrix elements have been deduced for the angular-momentum sublevels.

A calculation is made of the steady-state acceleration of electrons by parametrically excited Langmuir waves in a spatially homogeneous plasma. Collisions are accounted for by a simple relaxation model. An algebraic expression is given for the number density of hot electrons.

Existing theoretical ${\mathrm{H}}_2$ pair potentials are investigated. We develop a spherically symmetric potential applicable to solid ${\mathrm{H}}_2$. It yields a ground-state energy of -98.7 K (experimental values range from -93.5 to -101 K). Pressure-volume data are also in excellent agreement with experiment between 0 and 25 kbar. Second virial coefficients using this potential are consistently too low. When an anisotropic pair potential is used, agreement becomes very good.

An exact solution of a new superconducting state is obtained which exists for dc currents larger than the critical current in thin wires. The order parameter is zero at all times at certain points in the whisker, thereby permitting the phase to slip at a constant rate, a consequence of which is a dc potential difference between the separate singly connected superconducting regions. These solutions are periodic in space and stable in time and lead to voltage steps in the dc $V-I$ characteristic.

The lattice transformation temperature $T_L$ of single-crystal ${\mathrm{V}}_3$Si was directly observed to decrease linearly with hydrostatic pressure at a rate of -(1.5 ± 0.1) × ${10}^{-4\mathrm{}}$ °K ${\mathrm{bar}}^{-1\mathrm{}}$. To explain the pressure dependence of $T_L$ and the elastic behavior, the Labbé-Friedel model must be extended to include interband charge-transfer effects as a new variable, in agreement with a recent calculation of Ting and Ganguly. We give a discussion of these results related to structural instability and superconductivity.

Measurements of the specific heat of tetrathiofulvalinium-tetracyanoquinodimethane have been made from 45 to 70 K using ac calorimetric methods. A steplike anomaly in the specific heat is observed with transition temperature 54.8 K. The results compare favorably with predictions from a mean-field model when the crystal undergoes a Peierls distortion.

The high-pressure form of cerium metal stable above 56 kbar is found to be orthorhombic with the $\alpha$-uranium type of structure. The effective metallic radius and the observed compressibility correspond to full tetravalency for cerium. A second, metastable form of cerium metal with a monoclinic structure has also been observed above 60 kbar.

A method which represents surface electronic structure exactly in terms of local functions is tested by applying it to a one-dimensional surface potential. A single four-parameter variational calculation yields continuum and surface-state wave functions for an entire perturbed band. Comparison with exact solutions obtained independently indicates that the calculation is quite accurate.

Ions liberated from an adsorbed layer by electron-stimulated desorption are shown to have sharply peaked, symmetric angular distributions which are in registry with the substrate. We propose a new method for investigation of the symmetry of binding sites for adsorbed species.

Luminescence at 368 nm from crystals containing ${\mathrm{Eu}}^{2+}$ exhibits the small spectral shifts from host to host typical of a parity-forbidden rare-earth transition, and yet has the emission oscillator strength ($f\gtrsim 1$) of a highly allowed transition. It is improbable that this anomaly can be trivially resolved, e.g., in terms of measurement errors, stimulated emission, or impurity involvement.

The ground-state nuclear magnetic moment of ${}_{}{}^{207}{}_{}{}^{}\mathrm{Bi}$ has been measured by nuclear orientation in the hyperfine field of a nickel host. The unperturbed anisotropy of the 1770-keV $\gamma$ ray gives the results $\mu =(4.63\mathrm{}\pm 0.25){\mu }_N$ and ${\left[\delta \right(\frac{E2\mathrm{}}{M1\mathrm{}}\left)\right]}_{1770}=-0.0836\mathrm{}\pm 0.0030$. Strongly attenuated anisotropies are observed for $\gamma$-ray transitions which pass through the 0.8-sec isomer in ${}_{}{}^{207}{}_{}{}^{}\mathrm{Pb}$, and these are quantitatively explained in terms of a perturbing quadrupole interaction in this state.

We show that if the $P$-wave interaction volumes relevant for construction of the pionnucleus optical potential used in pionic-atom studies turn out to be simply related empirically to the free-space pion-nucleon scattering volumes, then this would be indicative of both sets of quantities being dominated by the $\Delta \left(1236\mathrm{} \mathrm{MeV}\right)$, which can be treated as an independent baryonic excitation in nuclei. Within this framework, we give a simple derivation of modifications to the optical potential coming from baryon-baryon short-range correlations.

The real part of the bound-atom coherent neutron scattering length of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ has been measured by comparing the reflectivities of quartz-liquid-${}_{}{}^3{}_{}{}^{}\mathrm{He}$ and quartz-liquid-${}_{}{}^4{}_{}{}^{}\mathrm{He}$ interfaces and has been found to have the value (6.1 ± 0.6) × ${10}^{-13\mathrm{}}$ cm.

Mixed-configuration shell-model wave functions predict the sort of two-nucleon transfer phenomena which has been interpreted as evidence for weak coupling to excited $0^{+}$ states.

Forty directly produced electron pairs have been found by following 713.4 m of 200-GeV-proton track length in nuclear emulsion. For these pairs we have analyzed (i) the total energy distribution, (ii) the energy partition between the two members, (iii) the angular divergence, (iv) the transverse momentum distribution, and (v) the invariant mass of the electron pairs. Present theories disagree with our experimental results.