Strong plasma heating is observed in external electric fields near the upper hybrid frequency or near the electron cyclotron harmonics. It is shown that the fast plasma heating is associated with the presence of the parametric instability of Bernstein waves, ionacoustic waves, and lower hybrid waves.

Low-frequency oscillations, which can lead into the violent disruptive instability which sets the $\mathbf{q}$ (current) limit of tokamak operation, are investigated with a heavy-ion beam probe. Direct measurements of the space potential and the perturbation of the electron density inside the hot tokamak plasma resolve the electric field contribution to the mode rotation and the spatial structure of the mode.

A nuclear cooling system consisting of copper wire was connected to a copper container inside of which a copper powder had been compressed and sintered. The heat capacity of the system without ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ in the container was subtracted from the heat capacity with ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ at pressures ranging from 0 to 29 atm. The difference shows a peak at 1.5 mK which decreases in magnitude as the pressure is reduced and a broad shoulder extending up to about 3 mK which is present at all pressures.

A direct comparison has been made of electron-excited soft-x-ray appearance potentials, which are surface sensitive, and photon-excited Auger-electron appearance potentials, which are more characteristic of bulk atoms. A single tungsten emitter served as a reference for both measurements. The "surface chemical shifts" thus obtained for the $2p_{\frac{3}{2}}$ levels of Ti, Cr, and Ni are in reasonable agreement with predictions based on a muffin-tin approximation of overlapping one-electron potentials.

Correlation effects are included in a detailed theoretical study of the multiplet structure observed by x-ray photoelectron spectroscopy. This correlated multiplet hole theory resolves the difficulties of earlier multiplet hole theory studies: It correctly determines the magnitude of the observed $2\mathbf{s}$ and $3\mathbf{s}$ (doublet) splittings and their intensity rations, and predicts the existence of new structure for the $3\mathbf{s}$ binding energy splittings—structure which does not exist in one-electron theory and which has now been confirmed by Kowalczyk et al.

The conductivity of gas-free thin films of amorphous germanium was measured as a function of temperature and film thickness. Existing theories of hopping conduction have been modified to apply to very thin films. The results are consistent with experiment, indicating that hopping conduction near the Fermi energy is the mechanism responsible for the conductivity below room temperature. The radius $a$ of the localized wave functions and the density of states $N_{\mathrm{F}}$ at the Fermi energy found are $a=10\mathrm{}$ Å and $N_{\mathrm{F}}=1.5\mathrm{}\times {10}^{18}$ ${\mathrm{eV}}^{-1\mathrm{}}$ ${\mathrm{cm}}^{-3\mathrm{}}$.

This work centers on the now disputed interpretation of the observed $T^{-\frac{1}{4}}$ dependence of the conductivity in amorphous group-IV semiconductors by hopping near the Fermi energy. We find the arguments against this interpretation inapplicable. We present experimental results of the temperature dependence of the resistivity $\rho \mathrm{}\left(T\right)\mathrm{}$ of gas-free and void-free amorphous germanium, as well as theoretical results of $\rho \mathrm{}\left(T\right)\mathrm{}$ for a hopping model with a band of localized states near the Fermi energy. The agreement is good and leads to the estimate of the bandwidth of 0.3 eV.

The first detailed application of a general anisotropic exchange operator to energy-transfer problems in magnetic insulators is described for exciton dispersion in Gd${\mathrm{Cl}}_3$ and Gd${\mathrm{}\left(\mathrm{OH}\right)\mathrm{}}_3$. Relationships, which are independent of the two parameters in the theory and are consistent with experiment, are found between transfer-of-energy matrix elements for different excited states, providing strong evidence that anisotropic exchange is the dominant mechanism of energy transfer.

We have recorded and analyzed spectra of x rays following proton and $\alpha$-particle bombardment of heavy atoms. The normal $K$ x rays are accompanied by satellite peaks originating from nuclear reactions. The phenomenon is very intense in $\alpha$-induced reactions and it is correlated with $\alpha ,xn$ cross sections; in the case of proton bombardment the intensity of the phenomenon is surprisingly weak. It is presumed that the ionization is due to internal conversion of residual $\gamma$ rays.

A 79-MeV ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$ beam and counter-telescope techniques were employed to observe the reaction ${}_{}{}^{26}{}_{}{}^{}\mathrm{Mg}$(${}_{}{}^7{}_{}{}^{}\mathrm{Li}$, ${}_{}{}^8{}_{}{}^{}\mathrm{B}$) ${}_{}{}^{25}{}_{}{}^{}\mathrm{Ne}$. The cross section to the ground state was ∼ 350 nb/sr at forward angles and its $Q$ value was -22.05±0.10 MeV, corresponding to a ${}_{}{}^{25}{}_{}{}^{}\mathrm{Ne}$ mass excess of -2.18±0.10 MeV. Five excited states were also observed at 1.65±0.05, 2.03 ±0.05, 3.25±0.08, 4.05±0.08, and 4.7±0.1 MeV.

A simple theory of fermion pair composites is described and applied to the situation where, at low density, Bose condensation into the lowest self-consistent composite state takes place.

We have measured the cross section for the process $e+p\to e^{\prime }+p+{\eta }^0$ near threshold for values of the four-momentum transfer between 0.15 and 1.5 ${\left(\frac{\mathrm{GeV}}{c}\right)}^2$. Assuming that the cross section is dominated by production of the $S_{11}\mathrm{}\left(1535\right)\mathrm{}$ resonance, we have compared our data with quark-model calculations which predict the transition matrix elements for the reaction $e+p\to e^{\prime }+S_{11}\mathrm{}\left(1535\right)\mathrm{}$.

We have measured the ratio $\frac{\Gamma ({K_L}^0\to {\pi }^{+}{\pi }^{-})}{\Gamma ({K_L}^0\to \mathrm{a}\mathrm{l}\mathrm{l}\mathrm{c}\mathrm{h}\mathrm{a}\mathrm{r}\mathrm{g}\mathrm{e}\mathrm{d})}$ to be (2.64 ± 0.09) × ${10}^{-3\mathrm{}}$, a value significantly higher than the current accepted world average of (2.00 ± 0.07) × ${10}^{-3\mathrm{}}$. This ratio, together with currently accepted values for the ${K_S}^0\to 2\pi$ branching ratio and ${K_{L,S}}^0$ lifetimes, yields a value of $\left|{\eta }_{+-}\right|=(2.23\mathrm{}\pm 0.05)\times {10}^{-3\mathrm{}}$.

We use a refinement of Landau's hydrodynamical model of particle production to predict the spectra of pions in the inclusive reaction $p+p\to {\pi }^{\pm }+$ anything at high energies. With one overall constant obtained by normalizing the total multiplicity at one energy, we find that both the transverse and longitudinal momentum spectra predicted by the theory are in good agreement with the existing data.

Gravitational-wave observations can be powerful tools in the testing of relativistic theories of gravity. Future experiments should be designed to search for six different types of polarization, and for anomalies in the propagation speed of the waves: $|c_{\mathrm{grav}\mathrm{waves}}-c_{\mathrm{em}\mathrm{waves}}|\gtrsim {10}^{-7\mathrm{}}{c}_{\mathrm{em}\mathrm{waves}}$. This Letter outlines the nature and implications of such measurements.

The extremely forbidden transition $2{}_{}{}^3{}_{}{}^{}S_1^{}{}_{}{}^{}\to {}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}$ at 625.56 Å has been observed in a He afterglow using time-resolved high-resolution spectrophotometric techniques. The spontaneous radiative transition rate was determined by measuring the photon emission rate from a known number of metastables at pressures of 0.05, 0.30, and 0.75 Torr. The value measured is 2.4× ${10}^{-4\mathrm{}}$ ${\sec }^{-1\mathrm{}}$ with an experimental uncertainty of a factor of 3.

A model is solved for a fluid of biaxial particles within a type of mean-field approximation. The results suggest that the phase diagram of such a fluid exhibits a special critical point where two second-order critical lines meet a first-order phase boundary in a sharp cusp. The features of the phase diagram suggest a new way to look for critical phase transitions and biaxial phases in liquid crystals.

We have studied the dynamics of the order-disorder phase transition in ${\mathrm{Ni}}_3$Mn by neutron-scattering techniques. The relaxation time constant for the long-range order is about 90 min at a temperature 15°C below the critical temperature, but closer to the critical temperature it increases by more than an order of magnitude. This critical slowing down varies as the reduced temperature to a power of 1.04 ± 0.09.

First-principles calculations of the electronic band structure for the layer-type compounds $2H-\mathrm{Nb}{\mathrm{Se}}_2$ and $2H-\mathrm{Mo}{\mathrm{S}}_2$ predict a 1-eV hybridization gap within the $d_{z^2}$ and $d_{\mathrm{xy}}$, $d_{x^2-y^2}$ manifolds of the metal-atom $4d$ bands. This produces a narrow (∼ 1 eV) filled valence band in $2H-\mathrm{Mo}{\mathrm{S}}_2$ and a half-filled conduction band in $2H-\mathrm{Nb}{\mathrm{Se}}_2$, in agreement with electrical, optical, and recent photoemission date.

Photoemission studies have shown that although energy bands calculated from a three-parameter local pseudopotential agree well with experiment for Si, similar calculations disagree with experiment for Ge by amounts of order 0.5-1.0 eV for many states in the valence band. All these discrepancies can be removed through the introduction of one additional parameter describing the effects of $3d$ core states in Ge.