The reactions ${\mathrm{B}}^{11}(\gamma , p{\gamma }^{\prime }){\mathrm{B}}^{10}$ and ${\mathrm{B}}^{11}(\gamma , n{\gamma }^{\prime }){\mathrm{B}}^{10}$ were observed at bremsstrahlung endpoint energies of 24 and 35 MeV. No evidence was found for the existence of the $\mathrm{T}=\frac{3}{2}$ component of the giant resonance in ${\mathrm{B}}^{11}$.

The magnetic susceptibility of a neutron gas at zero temperature, an idealization of neutron-star matter, is estimated for the realistic, soft-core nucleon-nucleon potential of Reid. For mass densities below twice that of ordinary nuclear matter, there is no sign of a ferromagnetically favorable instability of the normal ground state of the system, the effect of the interactions being to depress the magnetic susceptibility relative to its Fermi-gas value.

A consistent explanation of the observed galactic flux of high-energy $\gamma$ rays and the reported galactic x-ray flux is provided in terms of Compton scattering of cosmic-ray electrons with the submillimeter radiation observed recently. It is predicted that the flux of galactic x rays, relative to that of cosmic x rays, will increase with increasing energy. Thus, if an increased enhancement in the flux of high-energy (∼200-keV) x rays in going across the galactic equator is not observed, the existence, on a galactic scale, of the submillimeter radiation will be ruled out.

We measured the differential cross section for 12.4-GeV/c proton-proton inelastic scattering on circles of fixed energy loss in the c.m. system. We varied the inelasticity from 8 to 94% and covered much of the angular range. For essentially all inelasticities the dependence on ${P_{\perp }}^2$ is approximately $e^{-3\mathrm{}{P_{\perp }}^2}$. The absolute value of $\frac{d^2\sigma }{d\Omega \mathrm{dp}}$ also depends only weakly on energy loss.

The breakup of hadrons into their constituent quarks is considered in a simple model. It is demonstrated that the cross section for quark production with this mechanism could be in the millibarn range. Experimental evidence for such a process in cosmic-ray interactions is discussed.

The ratio of the hydrogen atomic magnetic moment to that of deuterium has been measured by spin-exchange detection of Zeeman ($\Delta F=0\mathrm{}$, $\Delta m_F=-1\mathrm{}$) transitions in an atomic hydrogen maser. The value of this ratio is found to be 1.000 000 009 4(14) in agreement with a recent theoretical calculation. The spin-exchange technique has also been used to measure the zero-field ground-state deuterium hyperfine frequency. The result is $\Delta \nu \left(\mathrm{D}\right)=327\mathrm{}384352.51\left(5\right)\mathrm{}$ Hz.

The temperature dependence of ultrasonic attenuation in superfluid ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ below 0.6 K is studied. It is shown that vertex corrections in the phonon self-energy improve the agreement with experiment, especially near the transition between the collisionless and collision-dominated regions. The introduction of one average lifetime for the relevant thermal phonons is critically examined.

A transition of Ce impurities from a magnetic to a nonmagnetic state has been observed in superconducting La: Ce alloys at high pressure. The critical pressure for maximum pair breaking in La: Ce alloys is lower for the fcc than for the dhcp phase. The highest transition temperature of an elemental superconductor (12°K) is reported for pure La at 140 kbar.

A sharp peak in the two-phonon Raman spectrum of diamond was first observed by Krishnan and has recently been shown to be at a frequency higher than twice the maximum single-phonon frequency by Solid and Ramdas. We interpret this peak as evidence for the existence of bound states of the two-phonon system. The repulsive anharmonic phonon-phonon interaction which splits the bound states off the two-phonon continuum is estimated for diamond.

The de Haas-van Alphen effect has been detected in the cubic perovskite-type bronzes ${\mathrm{Na}}_{0.93}$Mo${\mathrm{O}}_3$ and ${\mathrm{K}}_{0.92}$Mo${\mathrm{O}}_3$. These are the first observations of this effect in grossly nonstoichiometric compounds.

A first-order metal-insulator transition at room temperature has been found in Cr-doped ${\mathrm{V}}_2$${\mathrm{O}}_3$ as a function of both Cr concentration and pressure. This is shown to be a Mott transition in which the conduction electrons localize to form the insulator. A generalized phase diagram relating the metallic, insulating, and antiferromagnetic insulating phases is presented.

We have observed as many as 11 half oscillations in electroreflectance spectra of germanium at the direct edge (${{\Gamma }_8}^{+}\to {{\Gamma }_7}^{-}$) at room temperature. In addition, near the experimental sixth half oscillation where the light- and heavy-hole contributions are of opposite signs, we observe destructive interference which greatly modifies the signal line shape in that region. The experimental results also demonstrate that neither thermal broadening nor field inhomogeneity need be a problem in electroreflectance measurements.

The effects of spin alignment induced by a large external magnetic field have been observed in the optical reflectivity spectra of antiferromagnetic EuTe at 1.5 K. By comparison with the reflectivity spectra of ferromagnetic EuO, EuS, and EuSe, we conclude that we have observed the transition from an antiferromagnetic superlattice band splitting to the ferromagnetic exchange splitting that occurs with complete spin alignment at $H\sim 80$ kOe.

The spin-wave spectrum of ${\mathrm{K}}_2$Ni${\mathrm{F}}_4$ has been measured at 5.0°K and found to be extremely anisotropic with no measurable dispersion in the direction perpendicular to the Ni${\mathrm{F}}_2$ planes. A study of the temperature dependence of the two-dimensional magnons shows that even relatively long-wavelength spin waves ($\lambda \approx 110$ Å) show little renormalization or lifetime effects up to $\approx 1.1T_{\mathrm{N}}$.

X-ray photoelectron spectra indicate core-electron binding-energy splittings of ∼6 eV for the $3s$ levels in Mn${\mathrm{F}}_2$, MnO, and Fe${\mathrm{F}}_3$, and less pronounced effects on the $3s$ levels in Mn${\mathrm{O}}_2$ and Fe metal. These splittings are considerably reduced from free-ion predictions but agree well with calculations for Mn in a cluster environment. The $3p$ multiplet splittings are shown to behave in a quantitatively different fashion.

An analysis of electron-scattering experiments gives a nuclear charge distribution which (A) has a central depression of about 7%, (B) falls offf at the nuclear edge faster than the customarily used Fermi distributions, (C) has no detectable energy dependence, and (D) appears to have an undulation of rather small magnitude.

The calculated contribution of core polarization to the effective interaction between two nucleons in a nucleus is shown, for certain potentials, to be much larger in the random-phase approximation than in first-order perturbation theory. Collective quadrupole and (in one case) monopole excitations are responsible for this.

New data on the isospin-forbidden reaction ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}(d, {\alpha }_2){}_{}{}^{10}{}_{}{}^{}\mathrm{B}\mathrm{}\left(1.74\right)\mathrm{}$ disagree with Noble's proposed direct reaction via a $2^{+}$ doublet in ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$. In contrast to other studies, we find no convincing evidence that direct reactions contribute a major portion of the large isospin-forbidden cross sections.

Using the technique of an electron beam crossing a laser beam, an experiment is proposed not only for resolving the controversy of the electron mass-shift effect, but also for confirming the peculiar longitudinal and transverse motion of an electron in an electromagnetic traveling wave.

Continuity arguments for transitions between various subgroups of the chiral-symmetry group are presented. Some interesting sum rules are obtained in this way.