This paper reports calculations of the linear responses (the dielectric constant and the magnetic susceptibility) of an electron gas interacting through an exchange interaction with a set of localized magnetic moments. This allows one to account for the metal-semiconductor transition which has been observed in moderately doped EuO, in agreement with experimental data.

The spin-forbidden optical transitions of ${\mathrm{Co}}^{2+}$, ${\mathrm{Ni}}^{2+}$, and ${\mathrm{Mn}}^{2+}$ have been observed in doped crystals of Mg${\mathrm{F}}_2$ following both $\gamma$ and electron irradiation. Radiation-induced $F$ centers trapped at impurity sites appear to reduce the forbiddenness significantly for many of the transitions. Oscillator strength increases of up to ${10}^3$ have been recorded.

A theory based on the hypothesis that the perimeter wall of a magnetic bubble may be composed of alternate Bloch and Néel segments is shown to account quantitatively for the anomalous dependence of diameter on bias field of the recently observed "hard" bubbles in garnet films.

A theory is developed to explain the anomalous dynamic behavior of a new type of cylindrical magnetic domain called a hard bubble. This theory, which is based on the Landau-Lifshitz-Gilbert equation of motion, is able to explain satisfactorily all the salient features of the motion of hard bubbles.

Certain magnetic domain walls in a garnet film show a much reduced mobility from that of normal domain walls in the film and are interpreted to contain vertical Bloch lines. Theory shows that forward wall motion involves sideways propagation of Bloch lines and that in the high Bloch-line density limit, the mobility for small $\alpha$ is reduced to ${\alpha }^2$ of the conventional value, where $\alpha$ is the Gilbert damping parameter.

The difference between the polarization and the analyzing power in the inelastic scattering of protons at isobaric analog resonances in ${}_{}{}^{89}{}_{}{}^{}\mathrm{Y}$ has been determined by measuring the spin-flip probability of a polarized beam. The differences are large, and are sensitive to the structure of the resonances.

Neutron-deficient isotopes of bismuth and lead have been produced in various heavy-ion—induced reactions. Argon and krypton ions were used as projectiles on ${}_{}{}^{159}{}_{}{}^{}\mathrm{Tb}$, ${}_{}{}^{155}{}_{}{}^{}\mathrm{Gd}$, and ${}_{}{}^{109}{}_{}{}^{}\mathrm{Ag}$. We observed $\alpha$ emission from bismuth nuclides and isomers with $A=190-197\mathrm{}$ and from lead isotopes with $A=186-190\mathrm{}$. We give results on mass assignments, $\alpha$-decay energies, half-lives, and $\alpha$ branching ratios. Two new lead isotopes were found: ${}_{}{}^{187}{}_{}{}^{}\mathrm{Pb}$, $E_{\alpha }=6.08\mathrm{}$ MeV, $t_{\frac{1}{2}}=17.5\mathrm{}$ sec; and ${}_{}{}^{186}{}_{}{}^{}\mathrm{Pb}$, $E_{\alpha }=6.32\mathrm{}$ MeV, $t_{\frac{1}{2}}=7.9\mathrm{}$ sec. No $\alpha$-emitting isotopes of thallium were found, and upper limits significantly below 1% can be set on the $\alpha$ branching ratios of T1 isotopes with $A=182-187\mathrm{}$.

We have measured the differential cross section for radiative ${\pi }^{+}$ -proton scattering, ${\pi }^{+}p\to {\pi }^{+}p\gamma$, at 294 MeV under kinematical conditions favorable to the observation of radiation from the magnetic dipole moment of the ${\Delta }^{++}\mathrm{}\left(1236\right)\mathrm{}$ resonance. For radiated photon energies above 30 MeV, our data do not agree with explicit theoretical calculations which include an estimate of the magnetic moment radiation. Rather, our data agree with the simple expression in the c.m. system, $\frac{d\sigma }{d{\tilde{\Omega }}_{\pi }d{\tilde{\Omega }}_{\gamma }d{\tilde{E}}_{\gamma }}=\frac{{\sigma }_0}{{\tilde{E}}_{\gamma }}$, over the full range of photon energy, up to ${\tilde{E}}_{\gamma }=140\mathrm{}$ MeV. Preliminary measurements of radiative ${\pi }^{-}$ -proton scattering have also been made.

An investigation of double electron-positron pair creation was conducted using a quadrisected annulus of NaI with $\gamma$ rays of average energy 6.6 MeV impinging upon targets of copper, aluminum, carbon, and beryllium. The data, corrected for bremsstrahlung effects, were fitted by a linear function of atomic number in order to separate the instantaneous double-pair production process from the direct-cascade effect. The result of the measurement is given as $\frac{{\sigma }_{\pi \pi }}{{\sigma }_{\pi }}=(2.4\mathrm{}\pm 1.6)\times {10}^{-5\mathrm{}}$.

Starting from the recent U(3) $\otimes$ U(3) gauge model of strong interactions, we discuss the very natural synthesis with Weinberg's model of leptons. As a result of the interplay of the two models (a) neutral $\Delta S=1\mathrm{}$ currents are eliminated without enlarging the number of quarks, and (b) a natural $(3,\overline{3})\oplus (3,\overline{3})$ symmetry breaking emerges for the hadrons. Incorporation of alternative lepton theories is mentioned.

In experiments on violent ion-molecule collisions, we have observed that if the target molecule contains the lower-$Z$ atomic-collision partner, as in e.g., ${\mathrm{Ne}}^{+\to }$${\mathrm{N}}_2$, N${\mathrm{H}}_3$, the molecular nature of the target has no effect on the probability of producing $K$ vacancies. If, on the contrary, the target molecule contains the higher-$Z$ atomic-collision partner, as in, e.g., ${\mathrm{C}}^{+\to }$${\mathrm{N}}_2$, N${\mathrm{H}}_3$, an appreciable molecular effect is evident.

X rays produced by 10- to 60-MeV I-ion bombardment on thick Au, Th, and U targets were analyzed with a high-resolution Si(Li) detector. The spectra can be understood in the framework of diabatic molecular orbitals. Radiative transitions in the quasimolecule formed during the collision are observed. These transitions between transient molecular orbitals may be interpreted as $M$ x rays of superheavy quasiatoms with nuclear charges of $Z=132,143,\mathrm{and} 145$.

We observed thirteen laser magnetic resonance lines (transitions between $\mathrm{}[n=3,J=4\mathrm{}]\mathrm{}\to \mathrm{}[n=5,J=5\mathrm{}]\mathrm{}$ for the oxygen molecule, using the 337-μm line of the HCN laser. The magnetic $g$ factors ($g_{\perp }=2.0044\mathrm{}$, $g_z=2.0020\mathrm{}$, and $g_n=0.000\mathrm{}125$) give the best fit to the data. The zero-field frequency for the transition $\mathrm{}(N=J=3\mathrm{})\mathrm{}\to \mathrm{}(N=J=5\mathrm{})\mathrm{}$ obtained by using these sets of the magnetic $g$ factors all agree with theoretical value of 775.700 43 ±0.000 01 GHz if an experimental uncertainty of ± 1 G (± ${10}^{-4\mathrm{}}$ T) is allowed.

The breakdown field in a microwave cavity excited in the electric quadrupole mode exhibits a plateau at pressures below the electron mean-free-path limit of diffusion-controlled breakdown. The luminosity of a steady-state plasma in this domain exhibits a maximum at the central nodal point in the cavity field. These results are interpreted as evidence of rf confinement of a low-density plasma.

We describe a hydromagnetic dynamo utilizing Bénard convection between rotating parallel planes. The model is based upon an asymptotic expansion in two spatial scales valid for large Taylor number.

The coexistence curve of sulfur hexafluoride has been determined by interferometric measurements for the temperature range ${10}^{-5\mathrm{}}<\frac{(T_c-T)}{T_c}<{10}^{-1\mathrm{}}$. The refractive index difference $n_l-n_v$ is fitted by a power law. The difference $\Delta n$ is proportional to ${\left(\Delta T\right)}^{\beta }$, where $\beta =0.346\mathrm{}\pm 0.001$ for the temperature range ${10}^{-2\mathrm{}}<\frac{(T_c-T)}{T_c}<{10}^{-1\mathrm{}}$. The exponent $\beta$ decreases to 0.339 ± 0.003 as $\frac{(T_c-T)}{T_c}$ decreases to the lower limit of the data at ${10}^{-5\mathrm{}}$.

The statistical distribution of the scattered light intensity is studied theoretically and experimentally for systems where $〈N〉$, the average number of particles in the scattering volume, is small. An expression is obtained for the intensity distribution for the case of a uniformly illuminated scattering volume and the moments are obtained for an arbitrary illumination profile. Calculated moments are compared with those measured for dilute solutions of polystyrene spheres.

Flow of ${\mathrm{He}}^4$ films adsorbed on graphite is qualitatively different from flow on other substrates. We observe two distinct types of "onset" phenomena. Type $A$ appears for films thicker than 2 layers at temperatures $T_A$ within 20 mK of $T_{\lambda }$. In thicker films there is an additional more dramatic increase (onset $B$) at lower $T$. $T_B$ varies with $\frac{P}{P_0}$, and is higher than temperatures of "superfluid onset" reported previously.

Second-sound velocity measurements were made in He II near the tricritical point ($T_t,x_t$). The corresponding superfluid density along the coexistence curve can be described by $\frac{{\rho }_s}{\rho }=2.03\mathrm{}{\epsilon }_t ({\epsilon }_t\equiv 1-\frac{T}{T_t})$. This agrees with recent theories. At constant concentration $x$ and near the superfluid transition temperature $T_{\lambda }$, the results are consistent with $\frac{{\rho }_s}{\rho }\sim k_{\lambda }{{\epsilon }_{\lambda }}^{\frac{2}{3}} ({\epsilon }_{\lambda }\equiv 1-\frac{T}{T_{\lambda }})$ which is expected on the basis of universality arguments. The amplitude $k_{\lambda }$ becomes small for small $x_t-x$, but does not appear to vanish at $x_t$.

Localized coupling structures, such as open-ended wave guides located close to the plasma boundary, radiate a spectrum of electrostatic waves that are accessible to the lower hybrid layer in an inhomogeneous plasma. The energy flow is confined within narrow channels, similar to the resonance cone effect discussed by Fisher and Gould. Radical changes in the energy-flow picture result if the constant-density contours are aligned at a small angle [$\sim {\left(\frac{m_e}{m_i}\right)}^{\frac{1}{2}}$] to the magnetic field.