The cross-field current-driven ion acoustic instability occurs when electrons and ions have a relative streaming velocity (along $x$) across a weak magnetic field. For certain ranges of conditions, the spatial growth rate is enhanced over the value with no field. Measurements of the growth rate in two different plasma configurations as a function of both field and frequency give results consistent with the linear dispersion relation for this instability.

We present a model for the nonlinear evolution of the electron-plasma ion-acoustic decay instability when the ratio of electron and ion temperatures is of order 1. Ion nonlinear Landau damping is found to be the dominant saturation mechanism. We calculate the saturated spectral intensity and pump absorption coefficient. An estimate is given of the energy that the enhanced fluctuations absorb from an electromagnetic wave incident on an inhomogeneous plasma.

Electronic phase transitions in ${\mathrm{Ce}}_{1-x}{\mathrm{La}}_x$ alloys are investigated on the basis of the model recently proposed by Ramírez and Falicov. We analyze the influence of the La $4f$ level, and discuss implications on the behavior of pure La.

A kinetic method for measuring the properties of solid surfaces is described, and results are reported for the binding of helium on copper and copper thickly plated with argon.

Application of the methodology of analysis of Shockley surface states confirms the existence of Wannier's Stark ladders of energy levels in finite crystals for wave functions that decay exponentially towards both edges of the crystal and shows that the perfectly regular energy intervals will be minutely disturbed by tunneling effects. If phonon scattering is neglected, coherent oscillations of electrons associated with specified energy bands are predicted.

Kröner's equation for the stress field due to a continuous distribution of stationary dislocations is extended to the problem of moving dislocations. The equation governing the stress field takes the form ${\square }_T{\square }_L\chi =H$, where ${\square }_T$ and ${\square }_L$ are the d'Alembertian operators related to the velocities of the transverse and longitudinal sound waves, respectively. The expression for the stresses is also extended; it takes the form obtained from Kröner's equation by the substitution of d'Alembertian operators for the Laplacian.

The origin of electronic states in two classes of semiconductors is explored: (i) semiconductors containing group-VI elements in twofold coordination, and (ii) tetrahedral semiconductors. In the first case the valence band arises from the unshared electron pair (lone pair) of the group-VI atom. We examine the effects of compositional variation on the distribution of states in amorphous semiconductors. It is predicted that an Anderson transition will occur in the band of lone-pair states when a group-VI element is added to a tetrahedral amorphous semiconductor.

The trapping of positrons at vacancy sites in some metals provides a new and sensitive method for the equilibrium determination of vacancy-formation energies. Data are presented for Al, Cd, In, Pb, and Zn and fitted to a model allowing presentation in the form of Arrhenius plots. The vacancy concentration is not determined because it appears as a product with the positron trapping rate.

We solve the Falicov-Kimball model of the metal-insulator transition in the coherent-potential approximation. This yields exact results in certain limits in which molecular field theory is incorrect, and it is a better approximation over the whole range of the parameters. We find that, at least below the point at which bound states appear, all phase transitions vanish.

Holmium exists in low-temperature conical and intermediate-temberature spiral magnetic phases, implying a temperature-dependent variation of effective anisotropy. We show that if this anisotropy is varied from the spiral to the conical region there will first be a second-order transition to an intermediate phase whose order is essentially a tilted spiral and then a first-order transition to the cone. The intermediate phase might be found at around 20 K.

The static electric quadrupole moment of the $2_1^{}{}_{}{}^{+}$ state in ${}_{}{}^{42}{}_{}{}^{}\mathrm{Ca}$ was measured to be $(-18.9\mathrm{}\pm 8.1)e$ ${\mathrm{fm}}^2$. A $B(E2;{2_1}^{+}\to {0_1}^{+})=(81.5\mathrm{}\pm 3.0)e^2$ ${\mathrm{fm}}^4$ was obtained. The $E2\mathrm{}$ properties of the lowest seven levels were used to decompose the levels into ${\mathrm{}\left(\mathrm{fp}\right)\mathrm{}}^2$ states plus a deformed band with ${\beta }_2=+0.375\mathrm{}\pm 0.006$. The band structure, moments of inertia, and ${\beta }_2$ values in ${}_{}{}^{42}{}_{}{}^{}\mathrm{Ca}$ and ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ are nearly identical, implying that the lowest $K=0^{+}$ band in ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ is also prolate.

The possibility is discussed that the observed energy dependence of the real part of the optical potential in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$-${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ elastic scattering arises from rotation of nuclei induced by their interaction. An estimate indicates that the effect may have the required magnitude.

We study the proton entrance width for formation of double-analog states in heavy nuclei. A channel-coupling term gives the dominant contribution to this isospin-forbidden width. Pairing correlations in the parent nucleus enhance this width by a large factor. It is about 80 eV for the double analog of the ground state of ${\mathrm{Pb}}^{210}$, and larger (1 keV) in the region of the tin isotopes.

Transfer of polarization to the residual nucleus in a nuclear reaction has been observed by combining the use of a vector-polarized deuteron beam with Mössbauer measurements of magnetic sublevel populations. A large transfer of polarization was seen in the reaction ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}\mathrm{}(d,p)\mathrm{}{}_{}{}^{57}{}_{}{}^{}\mathrm{Fe}_{}^{*}{}_{}{}^{}$ terminating in the 14.4-keV state of ${}_{}{}^{57}{}_{}{}^{}\mathrm{Fe}$, consistent with a simple polarization-transfer mechanism. The method is applicable to a number of reactions leading to Mössbauer final states.

We have found $g_{\frac{9}{2}}$ analog resonances in the reactions ${}_{}{}^{58,60,62}{}_{}{}^{}\mathrm{Ni}(p,\gamma ){}_{}{}^{69,61,63}{}_{}{}^{}\mathrm{Cu}$ and ${}_{}{}^{64,66}{}_{}{}^{}\mathrm{Zn}(p,\gamma ){}_{}{}^{65,67}{}_{}{}^{}\mathrm{Ga}$ with strong $M1\mathrm{}$ transitions to the corresponding antianalog states.

Magnetized stars contracting to neutron star dimensions or collapsing to a black hole will emit large quantities of electromagnetic radiation. It is shown that under favorable circumstances cosmic rays can be generated with energies in excess of ${10}^{21}$ eV.

The relations between the quantized gravitational field and its curved space-time background are studied. Some restrictions on the geometrical quantization of the gravitational field are then deduced in the framework of axiomatic field theory. This shows the necessity of the introduction of the formalism developed in an earlier paper.

The production of 12 849 $K^0$'s by $K^{+}d$ charge exchange at 615 $\frac{\mathrm{MeV}}{c}$ and the subsequent decays occurring within 6 $K_s$ mean lifetimes were observed in the Brookhaven National Laboratory 30-in. bubble chamber. The results are $\mathrm{Re}\delta =-0.0017\mathrm{}\pm 0.0072$ (where $\delta$ is the $\mathrm{CPT}$-nonconserving parameter), $\frac{\mathrm{rate}(K_s\to {\pi }^{+}{\pi }^{-})}{\mathrm{rate}(K_s\to {\pi }^0{\pi }^0)}=2.22\mathrm{}\pm 0.08$, and $\frac{\mathrm{rate}(K_s\to \gamma \gamma )}{\mathrm{rate}(K_s\to \mathrm{all})}<~2\times {10}^{-3\mathrm{}}$ (90% confidence level).

Contrary to common belief, fluorescence from high vibrational levels of the lowest excited electronic singlet state of certain complex molecules in liquid and solid solution is observable and can be a valuable spectroscopic tool for the study of intramolecular energy-transfer processes. Several such fluorescent levels were identified in magnesium phthalocyanine in $\alpha$-chloronaphthalene with quantum efficiencies of the order of ${10}^{-3\mathrm{}}$ at 77°K and ${10}^{-4\mathrm{}}$ at 300°K in the visible spectral region.

Electric-field-induced anticrossing signals of $n=5\mathrm{} {\mathrm{He}}^{+}$ are detected by intensity changes of the line He II 4686 Å ($n=4\mathrm{}$ to $n=3\mathrm{}$). The fine structure splittings $5^2{S}_{\frac{1}{2}}-5^2{G}_{\frac{7}{2}}$ and $5^2{S}_{\frac{1}{2}}-5^2{\mathrm{G}}_{\frac{9}{2}}$ have been derived from the measurements to be 15 924.4 ± 5.9 and 17 040.5 ± 8.0 MHz, respectively, in agreement with the theoretical values of 15 920.0 and 17 043.6 MHz. The splitting $5^2{G}_{\frac{7}{2}}-5^2{G}_{\frac{9}{2}}$ is 1116.1 ± 14.0 MHz compared with the theoretical value of 1123.6 MHz.