A microscopic theory of lattice dynamics of ionic crystals is developed in terms of non-orthogonal highly localized wave functions. It is shown that this approach is in close correspondence to some shell models and leads to a microscopic understanding of the model parameters. The phonon dispersion of LiD has been calculated without using any adjustable parameters and it agrees with experiment to within 10% on the average.

Renormalization-group recursion relations are used to calculate to order $\epsilon =4-d$ the free-energy, ordering-susceptibility, and magnetization-crossover scaling functions for tricritical points in isotropic $n$-vector models. The equations of state describe critical and tricritical behavior in both ordered and disordered phases.

We report accurate measurements of the electrical conductivity of the semiconducting liquid ${\mathrm{Tl}}_x{\mathrm{Se}}_{1-x}$ over the temperature range $250°\mathrm{C}\lesssim T\lesssim 500°\mathrm{C}$, and composition range $0.002<~x<~0.377$ (as well as $x=0\mathrm{}$). The conductivity is thermally activated for all temperatures and compositions studied and its behavior is consistent with a changeover in conduction mechanism as $x$ increases from zero. We interpret the $x>\mathrm{}0\mathrm{}$ results in terms of percolative hopping.

In a previous Letter the author presented the exact ground-state wave function for a one-dimensional plasma with short-range polarization forces and a uniform background of opposite charge. In this Letter it is proven that the ground state has long-range crystalline order, and thus is an example of the Wigner solid. The $n$-particle density matrices are evaluated in closed form.

With the use of recent observations of the galactic gas and $\gamma$-ray distributions, the galactic cosmic-ray distribution is deduced. This distribution is identical to that of supernova remnants (within experimental error), strongly supporting the hypothesis that most observed cosmic rays are produced by supernovae in our own galaxy. The average age of the cosmic-ray sources is suggested from the character of their distribution to be about 30 million years.

Magnetic susceptibility, heat capacity, and EPR studies reported here show that close to 50% of the high-spin ${\mathrm{Fe}}^{3+}$ ions in this compound form isolated spin pairs each of which shows a highly anisotropic superexchange coupling. Direct EPR transitions between the superexchange-split energy levels have been observed.

The superconducting transition temperature $T_c$ of aluminum has been measured as a function of pressure to 62 kbar, at which point $T_c$ was reduced to 0.075 K from its zero pressure value of 1.18 K. These data cover ranges of temperature and pressure which allow differentiation between theoretical and empirical predictions. The data clearly obey the empirical relation of Smith and Chu and suggest a new volume dependence for the electron-phonon interaction.

The excitation spectra of $\mathrm{Si}\mathrm{}\left(2p\right)\mathrm{}$ and $\mathrm{O}\mathrm{}\left(1s\right)\mathrm{}$ core electrons, measured by low-energy electron-loss spectroscopy, yield detailed information on the excited states of Si, SiO, and Si${\mathrm{O}}_2$. The presence of an empty surface state near the top of the valence band on clean Si is directly demonstrated for the first time. For Si${\mathrm{O}}_2$, the results indicate the presence of five empty states in the conduction band.

Band theory and phonon measurements are used to calculate the electron-phonon coupling constant $\lambda$ for Pd and PdD. The results indicate that superconductivity is absent in Pd metal because of the large value of the Coulomb pseudopotential ${\mu }^{*}$, and that superconductivity occurs in PdD primarily because of coupling with the optic phonons. These results are consistent with superconducting transition-temperature measurements for these systems.

Both experimental measurement and theoretical calculations of the Compton profiles of LiF indicate a significant anisotropy in the electron momentum distribution whereas published x-ray structure-factor data indicate a lack of anisotropy in the charge density. In this paper we show that momentum distributions can be orders of magnitude more sensitive to anisotropy in the electron distributions than x-ray structure factors, at least in materials where the overlap of the wave functions is small.

Synchrotron-radiation photoemission data are obtained from GaAs ($\overline{1}\overline{1}0$) and (110) faces for $s$ and $p$ polarization which show an enhancement of valence-electron emission for initial states at and below the valence-band maximum when the photon energy is scanned through the threshold for Ga-$3d$-core to intrinsic-surface-state excitations. The enhancement is interpreted as a core surface exciton associated with the Ga dangling bonds.

It is shown that a two-dimensional energy band with saddle points at the Fermi energy is unstable against charge density wave formation. The distorted phase is metallic with only a relatively small area of Fermi surface truncated at the saddle points. It is suggested that this model applies to the layer compounds $2H$-Ta${\mathrm{Se}}_2$, $2H$-Ta${\mathrm{S}}_2$, $2H$-Nb${\mathrm{Se}}_2$, and 4Hb-Ta${\mathrm{S}}_2$.

We propose as an addition to the conventional charm-changing charged current the $V+A$ current ${\overline{\mathcal{P}}}^{\prime }{\gamma }_{\mu }(1-{\gamma }_5)\mathfrak{N}$. It explains the observed enhancement of nonleptonic $\Delta I=\frac{1}{2}$ weak decays, allows low-lying charmed hadrons to decay comparably into strange and non-strange final states, predicts the appearance of ${\mu }^{-}{l}^{-}$ (as well as ${\mu }^{-}{l}^{+}$) dilepton events in neutrino interactions, and leads to copious quasielastic charm production by neutrinos.

We have measured the production cross section for prompt muons relative to pions, produced in nucleon-nucleus interactions at incident energies from 30 to 300 GeV and for muon transverse momenta from 1 to 2.3 GeV/c. Upper limits on the production and leptonic decay of heavy particles are presented.

We present the results of a search for charged two-body decays of neutral high-mass resonances produced via neutron dissociation. The spectrometer, located in the M-3 beam at Fermilab, was sensitive to final states produced forward ($x>\mathrm{}0.3\mathrm{}$) with charged multiplicity ≲ 4. We find no significant enhancement in the high-mass $K^{\pm }{\pi }^{\mp }$ or $p{K}^{-}$ systems. The cross section times branching ratio is ≲ 50 nb/nucleon for $K\pi$ masses between 2 and 3 GeV.

I show, for the standard theory of radiative muon capture including all couplings except $g_S$ and all usual diagrams, that the photon asymmetry $\alpha$ and circular polarization $\beta$ satisfy $\alpha =+1+O\left(\frac{1}{m^2}\right)$ and $\beta =+1+O\left(\frac{1}{m^2}\right)$, where $m$ is the nucleon mass. This may bear on current disagreement between ${\alpha }^{\mathrm{theor}}$ and ${\alpha }^{\mathrm{expt}}$ since $O\left(\frac{1}{m^2}\right)$ terms have never been calculated consistently and since other uncalculated corrections, some of which are discussed, may contribute in the same order.

We have developed a photoionization method for complete conversion of a quantum-selected population to ionization, making possible sensitive and absolute measurement of the selected populations in a gas. Each photoionization involves the absorption of two photons (from a pulsed dye laser), one of which is resonant with an intermediate state. In this demonstration we measured the absolute number of $\mathrm{He}\left(2\mathrm{}{}_{}{}^1{}_{}{}^{}S\right)$ states per ion pair following interaction of pulses of 2-MeV protons with He.

Strong new visible emission bands are observed when mixtures of Cs of Rb with noble gases are excited with blue lines of an argon-ion laser. The bands in Cs are believed to be due to transitions between $7s\sigma$ bound excited states and dissociating $6s\sigma$ ground states of alkali-noble-gas molecules, and they may have potential for excimer laser systems.

We have obtained symmetric envelope solitons in two and three dimensions in a medium with a saturated nonlinear susceptibility given by ${\chi }_{\mathrm{NL}}\sim \exp (-{\left|\phi \right|}^2)-1\mathrm{}$, where $\phi$ is an appropriately normalized field amplitude. Examples for an electromagnetic wave and an electrostatic wave trapped in a plasma are presented.

The combination of multiply reflected electrons and positive ion flow in a reflex triode arrangement is analyzed. Under certain conditions it is possible to generate very intense beams of positive ions with this device. The analysis demonstrates that the energy loss and scattering of the electrons as they pass through the anode have a major effect on the ion and electron currents. Solid fractional-range anodes are shown to produce more intense ion beams than semitransparent mesh anodes.