Through NMR investigation of quadrupolar effects in some amorphous alloys (${\mathrm{La}}_{75}$${\mathrm{Ga}}_{25}$, ${\mathrm{Mo}}_{70}$${\mathrm{B}}_{30}$, ${\mathrm{Mo}}_{48}$${\mathrm{Ru}}_{32}$${\mathrm{B}}_{20}$, ${\mathrm{Ni}}_{78}$${\mathrm{P}}_{14}$${\mathrm{B}}_8$) the local symmetry is determined around the $s-p$ element sites. A comparison with the corresponding crystalline compounds (${\mathrm{La}}_3$Ga, ${\mathrm{Mo}}_2$B, ${\mathrm{Ni}}_3$B) which have typically different crystal structures (cubic, tetragonal, orthorhombic, respectively) gives conclusive evidence that the amorphous structure retains to a significant extent the local symmetry of the crystalline counterpart.

Calculations of the temperature dependence of mobility have been carried out for silicon (001) inversion layers in which Coulomb scattering and surface roughness scattering, but not phonon scattering, are included. The wave-vector and temperature dependence of screening contribute to a temperature-dependent part of the scattering rate that increases approximately linearly with temperature from 0 to 40 K. The results are supported by recent experiments of Cham and Wheeler.

The temperature dependence of the resistivities of $n$-type silicon inversion layers at liquid helium temperatures was studied in detail. The temperature dependence was found to be correlated to the mobility of the sample. Our results can be explained by Coulomb scattering, with possible contributions by surface-roughness scattering in high-mobility samples.

The role of the local-field effect in differential reflectance spectroscopy is studied within a classical model for an ordered overlayer of a weakly adsorbed species on a metal substrate. Results for Ar on Al at two coverages strongly indicate the importance of the local-field effect in such optical studies.

This Letter demonstrates that the nonrelativistic approximation breaks down for the lighter hadrons with the conventional $\mathrm{qq}$ one-gluon exchnage potential. This is mainly due to the Coulomb and the short-range hyperfine interactions. To overcome this difficulty, some phenomenological interactions with a long-range spin dependence are proposed. The validity of treating the spin-dependent term as a perturbation is examined.

The depolarization parameter for $\mathrm{pp}$ inclusive scattering at an incident momentum of 6 GeV/c was measured. The $D$ parameter for inclusive scattering indicates the dominance of natural-parity exchange at small $t$, except in the case of $N^{*}\mathrm{}\left(1232\right)\mathrm{}$ production, where $\pi$ exchange is more important. $D$ for elastic scattering has also been measured. This parameter shows a small decrease from unity with increasing momentum transfer.

A comparison of elastic scattering and total reaction cross-section data in the region of the $9^{-}$, 14.7-MeV resonance in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ + ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ is presented. The comparison provides firm evidence that there is very little background absorption of the $l=9\mathrm{}$ partial wave. The implications are discussed. A partial-width decomposition of the resonance is made.

The electric quadrupole moment of ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$ was determined by Coulomb scattering of aligned ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$ ions to be $Q=(-34\mathrm{}\pm 6)e$ mb. This compares favorably with the value $Q=(-41\mathrm{}\pm 6)e$ mb determined by atomic-beam spectroscopy.

Strong spin-isospin mode, $T=1\mathrm{}$, $T_z=1\mathrm{}$ analog states at 4.5 MeV in ${}_{}{}^{12}{}_{}{}^{}\mathrm{B}$ were studied by the reaction ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}(e, e^{\prime }{\pi }^{+}){}_{}{}^{12}{}_{}{}^{}\mathrm{B}$ at the electron energy $E_e=200\mathrm{}$ MeV. The photoproduction cross sections at seven angles ranging from 30° to 150° were obtained with use of virtualphoton theory and an experimentally determined real-to-virtual photon ratio. The results are compared with theoretical calculations and also with the available data on inelastic scattering from the 19.5-MeV $T=1\mathrm{}$, $T_z=0\mathrm{}$ analog complex in ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$.

Limits to the fusion of 310-MeV ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ with Ti were probed with both singles and coincience measurements of the heavy products and the emitted light particles. The upper limit to compound nucleus formation is found to be in accord with recent dynamic calculations, but the principal mechanism reducing the compound nucleus cross section below that predicted by critical distance models is not an increase in strongly damped processes, but the prompt emission of energetic light particles.

A revised shell-model level scheme is given for ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$, which takes into account the core-polarization effects. A new set of Woods-Saxon potential parameters are obtained for ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$, which are extrapolated up to mass number $A=500\mathrm{}$ and various neutron and proton magic gaps are observed.

This Letter presents the first experimental evidence of destructive interference effects in multiphoton ionization. The experiment involves a Cs atomic beam crossed with a linearly polarized dye-laser beam whose intensity reaches 20 GW/${\mathrm{cm}}^2$ in the 460-540-nm wavelength range. As predicted by second-order perturbation theory, the generalized ionization cross section exhibits a deep minimum which is found to equal (9±5)×${10}^{-52\mathrm{}}$ ${\mathrm{cm}}^4$ s at 480 nm. Discrepancies with previous experiments are tentatively explained.

The anisotropic interaction potential for Ne-${\mathrm{D}}_2$ is determined by a direct inversion method from the measured rotationally inelastic $j=0\mathrm{}\to j=2\mathrm{}$ and elastic $j=0\mathrm{}\to j=0\mathrm{}$ differential cross sections. The values obtained yield the repulsive part of the interaction in the range 2.43 to 2.77 Å. This is the first inversion of inelastic scattering data. The method is restricted to weak inelastic systems. It is computationally simple, and involves only errors of ∼ 5% in the inverted potential.

Three-dimensional ultracold-neutron focusing by a total-reflecting concave Fresnel-zone mirror has been observed. In the neutron wavelength range from 60 to 80 nm, real-image formation was achieved up to a magnification of 6. The measured image positions, magnifications, and intensities agree with expectation. Within the instrumental resolution no image broadening due to diffuse scattering has been observed.

An analytical model is developed for the nonlinear evolution of electron-ion two-stream instability. The instability saturates when the electric field energy reaches $\sim 2{\left(\frac{m}{M}\right)}^{\frac{1}{3}}{W}_0$ ($W_0=\mathrm{initial}\mathrm{electron}\mathrm{drift}\mathrm{energy}\mathrm{density}$), and is then followed by an algebraic growth. Complete stabilization is caused by electron trapping in deformed potential wells due to the rise of higher harmonics. The analytical model results are in close agreement with nonlinear kinetic computer simulations.

Time-resolved $\frac{3}{2}{\omega }_0$ spectra from glass microballoons irradiated by 100-ps, 2×${10}^{16}$-${\mathrm{W}}_{\mathrm{o}}$ ${\mathrm{cm}}^{-2\mathrm{}}$ laser pulses have been obtained with a temporal resolution of 20 ps and a spectral resolution of 15 Å. Pulsed emission is observed, with a pulse duration of less than the instrument limit. Both red and blue peaks appear simultaneously, with their separation varying in time.

The mechanism of nonlinear convective cell formation and the resulting diffusion in an inhomogeneous plasma is discussed. It is found that convective cells excited by nonlinear self-modulation of drift waves will cause strong anomalous diffusion also in systems where the linear convective cells are not dangerous.

With use of an expression for the $S$ matrix for the inelastic scattering of electrons from adatom vibrations, an explanation is given for the recently observed "specular selection rule" of Ho, Willis, and Plummer. The explanation is based upon (1) the existence of a $C_2$ axis of symmetry and (2) the assumption of nondegeneracy of the ground state of the solid.

Preliminary results are reported on the inelastic scattering of low-energy (20 meV), monoenergetic ($\frac{\Delta v}{v}=0.8\%$ full width at half maximum) He nozzle beams from a LiF(001) surface along the $〈100〉$ direction. The time-of-flight spectra reveal both broad and extremely sharp maxima. The broad maxima are attributed to a distribution of phonons of bulklike character with small momenta, while the sharp maxima indicate excitation of single discrete surface modes.

A model of spin-polarized hydrogen (H↑) is treated in which interactions between atoms are neglected while the single-atom Zeeman and hyperfine interactions are treated exactly. These magnetic terms in the Hamiltonian are found to affect substantially the Bose-Einstein condensation and the various thermodynamic variables. Computations are discussed of the condensation temperature, condensate density, and specific heat in order to indicate how changes in magnetic field strength might be expected to affect future measurements on this quantum system.