Brillouin spectra from thermally excited surface acoustic phonons in GaAs and Si surfaces coated with a thin Al film are presented. The measurements show features different from the Al and the semiconductor surfaces. We are able to give a theoretical explanation of the experimental results in terms of the coupling between the normal modes of the film and of the substrate.

We report an important drop in the longitudinal conductivity of TTF-TCNQ occurring at constant temperature in the metallic phase and in a narrow pressure domain located around 19 kbar. The drop of conductivity has been related to a × 3 commensurability of the longitudinal distortion with the lattice. This experiment, together with x-ray diffuse scattering of TTF-TCNQ could suggest that a significant fraction of the metallic conductivity below ambient temperature is due to the fluctuating collective mode.

The temperature dependence of the dielectric constant of Cs${\mathrm{H}}_2$P${\mathrm{O}}_4$ shows a crossover between a region ($3 \mathrm{K}<~T-T_c<~90 \mathrm{K}$) dominated by one-dimensional correlations and a region ($0 \mathrm{K}<~T-T_c<~3 \mathrm{K}$) dominated by three-dimensional correlations. A similar effect is observed as well in Cs${\mathrm{D}}_2$P${\mathrm{O}}_4$. The dielectric data allow for a quantitative determination of the ratio between the long-range interchain and the short-range intrachain coupling constants. ${}_{}{}^{31}{}_{}{}^{}\mathrm{P}$ and ${}_{}{}^2{}_{}{}^{}\mathrm{H}$ NMR data show that the ferroelectric transition is connected with an order of the H(2) hydrogens along the zig-zag chains.

We have measured the low-temperature magnetostriction in silver-rare-earth single-crystal and polycrystaline alloys at rare-earth concentrations of about 0.5%. For each monocrystal, the $〈100〉$ and $〈111〉$ magnetostrictions are of the same sign and follow the sign of the Stevens factor $\alpha$. Unannealed polycrystals show quite different behavior from the monocrystals.

If one compares pseudoscalar-coupled and pseudovector-coupled theories of the $\pi \mathrm{NN}$ interaction, which incorporate the restrictions of partial conservation of axial-vector current and realistic nuclear dynamics, then the amplitudes for exclusive ($p$,${\pi }^{+}$) or (${\pi }^{-}$,$n$) become identical, to $O\left(G^3\right)$.

Strong $\mathrm{CP}$ invariance is automatically preserved by a spontaneously broken chiral ${\mathrm{U}\left(1\right)\mathrm{}}_4$ symmetry. A weak-interaction singlet heavy quark $Q$, a new scalar meson ${\sigma }^0$, and a very light axion are predicted. Phenomenological implications are also included.

Fusion cross sections for the reactions $\alpha$+${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ and $\alpha$+${}_{}{}^{44}{}_{}{}^{}\mathrm{Ca}$ have been measured between 10 and 27 MeV (lab) via the detection of the $\gamma$ radiation of the evaporation residues. At maximum the cross sections are about 1170 mb for $\alpha$+${}_{}{}^{44}{}_{}{}^{}\mathrm{Ca}$ and about 970 mb for $\alpha$+${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$. This difference supports recent optical-model and semiclassical interpretations that the well-known anomalous large-angle scattering results from different absorption strengths for these two systems.

Continuum cross sections and spin polarizations of ${}_{}{}^{12}{}_{}{}^{}\mathrm{B}$ produced in the reaction ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$(${}_{}{}^{19}{}_{}{}^{}\mathrm{F}$, ${}_{}{}^{12}{}_{}{}^{}\mathrm{B}$) induced by 186-MeV ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}$ were measured. The observed data were reproduced very well in terms of a distorted-wave Born-approximation theory, indicating that this reaction transferring as many as seven nucleons proceeds as a direct process.

A model for radiative capture is described that is based on the same assumptions as the direct-semidirect model, but in which the giant resonance is explicitly projected out of the continuum space. Calculations on ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$($n$,$\gamma$) show that the model is much less sensitive to form-factor ambiguities than the direct-semidirect model, and that reasonable fits to data are obtained.

We demonstrate that polarized-proton radiative capture may be used to unambiguously identify concentrations of magnetic dipole strength. Three $M1\mathrm{}$ resonances are observed in the doubly magic ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ nucleus between $E_x=16\mathrm{} \mathrm{and} 20$ MeV, with a relatively large total ${\gamma }_0$-transition strength $B{\mathrm{}\left(M1\mathrm{}\right)\mathrm{}}_{\downarrow }>~0.24{{\mu }_0}^2$.

We report the observation of a laser-induced charge-transfer collision. In the presence of an intense laser beam, ground-state calcium ions collide with ground-state strontium atoms, selectively producing excited strontium ions and calcium neutrals. The laser-induced collision cross section has a linewidth of about 50 ${\mathrm{cm}}^{-1\mathrm{}}$ and peaks ∼ 70 ${\mathrm{cm}}^{-1\mathrm{}}$ from that wavelength which satisfies the energy defect of the separated atoms.

Optical-optical double resonance using two nitrogen-laser-pumped dye lasers has been used to make the first spectroscopic study of the hitherto unobserved gerade excited electronic states of ${}_{}{}^7{}_{}{}^{}\mathrm{Li}_2^{}{}_{}{}^{}$. Three ${}_{}{}^1{}_{}{}^{}{\Sigma }_{\mathrm{g}}_{}^{+}{}_{}{}^{}$ and two ${}_{}{}^1{}_{}{}^{}\Pi _{\mathrm{g}}^{}{}_{}{}^{}$ states are observed. Molecular constants in ${\mathrm{cm}}^{-1\mathrm{}}$ for one of the ${}_{}{}^1{}_{}{}^{}\Pi _{\mathrm{g}}^{}{}_{}{}^{}$ states are $T_e=31\mathrm{}868.02$, ${\omega }_e=229.71\mathrm{}$, ${\omega }_e{X}_e=1.654\mathrm{}$, $B_e=0.469\mathrm{}86$, ${\alpha }_e=0.005\mathrm{}959$, $D_e=7.301\mathrm{}$, and ${\mathcal{r}}_3=3.198\mathrm{}$ Å.

A classical-trajectory Monte Carlo method has been applied to collisions of two Rydberg atoms. Numerical calculations were made for velocities $v=0.01\mathrm{}{v}_e \mathrm{to} 10v_e$, where the Rydberg electron's velocity $v_e(\mathrm{a}.\mathrm{u}.\mathrm{})=\frac{1}{n}$ and $n$ is the principal quantum number of the Rydberg atom. The total ionization cross sections scale as $n^4$ and show a $v^{-0.65\mathrm{}}$ dependence at low $v$, a slight maximum around $v_e$, and a rapid decrease at high $v$. The cross sections are almost an order of magnitude larger than $\pi n^4{a_0}^2$ at thermal energies.

Dielectronic satellite spectra of Fe XXV near 1.8500 Å have been observed from PLT (Princeton Large Torus) tokamak plasma discharges for electron temperatures in the range from 1.5 to 3 keV and an electron density of 2×${10}^{13}$ ${\mathrm{cm}}^{-3\mathrm{}}$. The electron temperature was independently determined from the electron cyclotron radiation emitted by the plasma. The quality of the spectra allows a detailed comparison with theoretical predictions, which is of importance in view of diagnostic applications.

Two-dimensional computer simulations show that short-wavelength ion fluctuations and density-profile steepening are dominant factors in the saturation of the $2{\omega }_{\mathrm{pe}}$ instability. The long-term evolution of this instability is described and the implications of this complex saturation process for absorption and harmonic emission are discussed.

Structure functions of quenched off-critical binary mixtures are studied from a unified viewpoint. Individual systems are characterized only by the properties of their mobilities. The comparisons of theoretical predictions with experiments on the kinetic Ising spin model, binary fluid mixtures, and alloys yield with good agreement.

Measurements of the normal fluid density of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-$B$ from a high-$Q$ oscillator are reported which cover the pressure range 2 to 29 bars. These results indicate that to the accuracy of the measurements, 2% in temperature and 4% in density, all pressure dependence can be accounted for by a standard weak-coupling Fermi-liquid correction. The resulting stripped normal fluid density, however, displays a significant strong-coupling contribution which conflicts with theory and the interpretation of several other experiments.

Two glasses were investigated between 300 and 6 K, by means of forces Rayleigh scattering. Below approximately 50 K, unexpectedly strong scattering was observed. The source of the excess scattering is in local thermal equilibrium with the phonon bath above 20 K. A crossover to local relaxation is found below.

We present a theory to explain the anomalous enhancement of light scattering from molecules adsorbed at a metal-solution interface. It is found that tunneling of electrons between a surface molecule and the metal induces a resonance at a point in the vicinity of the Fermi surface. A dynamical equilibrium due to photoionization and recombination stabilizes the system near resonance.

We calculate the spin polarization of the 6-eV resonant satellite in Ni $3d$-band photoemission. The satellite is identified with the $3d^8$ configuration, and the resonant process involves the absorption $3p^{6}3d^9\to 3p^{5}3d^{10}$ followed by the super—Coster-Kronig transition $3p^{5}3d^{10}\to 3p^{6}3d^8\epsilon l$. The spin-up (majority) to spin-down (minority) intensity ratio is found to be approximately 4: 1 for the resonant process, whereas nonresonant Auger decay is found to be essentially unpolarized.