A phonon dispersion curve of Si is calculated using the microscopic theory of dielectric screening. The electron energies and wave functions are calculated from a crystal pseudopotential which is self-consistent with the electron-ion pseudopotential. For the polarizability matrix a continued fraction expansion including the zeroth and first moment is used. The first moment is treated as a constant. The results are sensitive to both the self-consistency condition and the closure approximation.

When the superconducting half of a superconductor-normal-metal film sandwich is a strong-coupling superconductor, phonon structure due to the superconductor (Pb)—but observed by tunneling into the normal metal (Ag)—provides a direct probe of the effective renormalization interaction in the normal metal. Unexpectedly, even fairly thick Ag films (≈ 350 Å) backed by Pb exhibit effective renormalizations approaching that of Pb, both in overall strength and energy dependence.

Evidence for the occurrence of a Bose-Einstein condensation of biexcitons in evaporated CuCl films is reported. It involves several unusual properties of the molecular luminescence under strong excitation.

We have measured the thermoelectric power of Nb${\mathrm{Se}}_3$ in the temperature range, 10-70 K, where charge-density-wave formation and strongly nonlinear conductivity has been reported. We report the first observation of an electric-field-dependent thermopower. Our results for Nb${\mathrm{Se}}_3$ show that in the presence of an electric field there is an additional negative contribution to the thermopower. Possible mechanisms which may account for this are discussed.

It is shown that the dynamical screening phenomena, which have recently been found to affect the shape of adsorbate core-hole spectra, occur also in the core ionization of certain molecules. For $K$-shell ionization of paranitroaniline we find shake-up transitions of negative energy which cause a multipeak structure of the corresponding line in the ESCA (electron spectroscopy for chemical analysis) spectrum. The present first-principles results lead to a new interpretation of the origin of the dynamical screening processes in adsorbates.

The Knight shift of negative muon (${\mu }^{-}\mathrm{Pd}$) in Pd metal has been determined to be - (9.0 ± 0.7)% at $T=11\mathrm{}$ K, revealing an unusually large hyperfine anomaly between ${\mu }^{-}\mathrm{Pd}$ and its equivalent isotope $\mathrm{Rh}\mathrm{Pd}$; $\frac{H_{\mathrm{hf}}\left({\mu }^{-}\mathrm{Pd}\right)}{H_{\mathrm{hf}}\left(\mathrm{Rh}Pd\right)}=0.64\mathrm{}\pm 0.05$, or ${\epsilon }_{\mu }-{\epsilon }_N=-(36\mathrm{}\pm 5)\%$. Its implication is discussed in terms of the spatial distribution of the electron spin density in transition metals.

This paper presents a group-theoretic explanation of the geometric interpretation of solitons due to Lamb and Lund.

Using a neutron interferometer of the type first developed by Bonse and Hart for x rays, we have observed the effect of Earth's rotation on the phase of the neutron wave function. This experiment is the quantum mechanical analog of the optical interferometry observations of Michelson, Gale, and Pearson.

A four-quark mechanism is proposed which generates virtually the entire known spectrum of (noncharm) meason states to remarkable accuracy. The ground-state $0^{-}$ and $1^{-}$ nonets are taken as input; exclusive of octet-singlet mixing there are no free parameters.

We report on the measurement of the reaction $e^{+}{e}^{-}\to e^{+}{e}^{-}$ with a large—solid-angle electromagnetic shower detector at center-of-mass energies $\sqrt{s}=13\mathrm{} \mathrm{and} 17$ GeV. Comparison of our results with predictions of quantum electrodynamics shows excellent agreement in both the angular distribution and energy dependence. Values of cutoff parameters are also given.

We report the first measurement of the ratio $R=\frac{\left({\sigma }_{e^{+}{e}^{-}\to \mathrm{hadrons}}\right)}{\left({\sigma }_{e^{+}{e}^{-}\to {\mu }^{+}{\mu }^{-}}\right)}$ (with negligible $\tau$-lepton contribution) at a center-of-mass energy $\sqrt{s}=13\mathrm{}$ GeV and $\sqrt{s}=17\mathrm{}$ GeV, from the just finished electron-positron colliding-beam facility PETRA. The detector, MARK-J, has an approximately $4\pi$ solid angle and measures $\gamma$, $e$, $\mu$, and charged and neutral hadrons simultaneously. Our results yield $R(\sqrt{s}=17\mathrm{} \mathrm{GeV})=4.9\mathrm{}\pm 0.6 \mathrm{}\left(\mathrm{statistical}\right)\mathrm{} \pm 0.7 \left(\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t}\mathrm{e}\mathrm{m}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{c}\mathrm{ }\mathrm{e}\mathrm{r}\mathrm{r}\mathrm{o}\mathrm{r}\right)$, and $R(\sqrt{s}=13\mathrm{} \mathrm{GeV})=4.6\mathrm{}\pm 0.5 \mathrm{}\left(\mathrm{statistical}\right)\mathrm{} \pm 0.7 \left(\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t}\mathrm{e}\mathrm{m}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{c}\mathrm{ }\mathrm{e}\mathrm{r}\mathrm{r}\mathrm{o}\mathrm{r}\right)$. The ratio $\frac{R(\sqrt{s}=17\mathrm{} \mathrm{GeV})}{R(\sqrt{s}=13\mathrm{} \mathrm{GeV})}$ is 1.08±0.18.

Possible new hadrons containing massive stable quarks (e.g., color-sextet quarks) surviving as relics of the early stages of the big bang should be present in $Z>\mathrm{}1\mathrm{}$ nuclei at levels accessible to experiment (∼${10}^{-10\mathrm{}}$). Grand unified theories that explain the observed baryon asymmetry of the universe should not contain these new stable quarks unless they are prevented from evolving asymmetrically. Otherwise, the new hadrons would be as common as nucleons, which is clearly not the case.

A measurement of the fission probability of the isoscalar giant quadrupole resonance, excited by inelastic scattering of 120-MeV $\alpha$ particles, yields an upper limit of 0.01 for the fission probability of the isoscalar giant quadrupole resonance in ${}_{}{}^{232}{}_{}{}^{}\mathrm{Th}$, compared to 0.055±0.015 for the underlying continuum.

Time-dependent Hartree-Fock calculations using Coulomb interaction and modified Skyrme force have been performed for the ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$+${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ reaction at laboratory bombarding energy per nucleon of 7.4 MeV/amu. The energy loss, scattering angles, and charge widths are in good agreement with experiment.

The energy spectrum of electrons produced by multiphoton ionization of xenon atoms has been analyzed with a retarding potential technique. We have shown that the discrete absorption of photons above the six-photon ionization threshold was observable under specified conditions. A simple model based upon inverse bremsstrahlung gives a resonable agreement with the experiments.

Direct measurements of differential scattering cross sections for positron-gas-atom collisions are reported. The apparatus used exploits the time-of-flight technique. Results for positrons of mean energy 2.2, 3.4, 6.7, and 8.7 eV elastically scattered through angles between 20° and 60° by argon atoms are presented. Sources of experimental error are discussed and comparison with recent theoretical calculations is made.

We present experimental and theoretical excitation probabilities $\mathcal{P}$ and coherence parameters $\lambda$ and $\chi$ for ${\mathrm{Be}}^{+}$($2s\to 2p$) excitation in 2-15-keV ${\mathrm{Be}}^{+}$-Ne collisions with impact parameters near 1.6 a.u. The phase difference $\chi$ between the quantum-mechanical amplitudes for $M_L=0\mathrm{}$ and $M_L=1\mathrm{}$ substate excitation exhibits a rapid change near 4 keV, where $\lambda$, which measures the relative size of those amplitudes, approaches its maximum value of unity. Impact-parameter calculations of $\mathcal{P}$, $\lambda$, and $\chi$ predict the trends found experimentally.

A hollow cylinder of magnetite at 4 K has been subjected to the simultaneous action of constant axial magnetic field $\overrightarrow{\mathrm{B}}$ and low-frequency radial electric field $\overrightarrow{\mathrm{E}}$. The reaction torque, which appears in the magnetite as the electromagnetic angular momentum changes, has been observed for the first time. Preliminary results favor the Livens' reaction-force density $\frac{-\partial ({\epsilon }_0\overrightarrow{\mathrm{E}}\times \overrightarrow{\mathrm{B}})}{\partial t}$ and contradict the alternative $\frac{-\partial ({\epsilon }_0{\mu }_0\overrightarrow{\mathrm{E}}\times \overrightarrow{\mathrm{H}})}{\partial t}$ of Einstein and Laub which was followed by Abraham and is widely accepted by modern authors.

If two coherent electron beams originating from the same source interfere after one of the beams has been accelerated or decelerated by a few electron volts, a wave-mechanical beat phenomenon should occur. Continuously tunable optical radiation should be emitted. Feedback of this radiation within an optical cavity may turn the system into a free-electron laser.

A space-time analysis of a typical high-current TFR discharge has been performed in terms of the trapped-electron instability whose effects are likely to occur in this parameter range. The evolution of both the electron and ion temperatures is consistent with the transport induced by this instability, but not with other transport models described. The structure of the discharge is calculated and some properties are illustrated.