The behavior of shear Alfvén eigenmodes and the accompanied anomalous transport have been investigated. In the particle simulation, equilibrium thermal fluctuations associated with the eigenmodes have been observed to nullify the zeroth-order shear near the rational surface through the induced second-order eddy current, and, in turn, give rise to the formation of magnetic islands which cause rapid electron energy transport in the region. The theoretical verification of the observed behavior is discussed.

Low-energy-electron-diffraction and Auger-electron-spectroscopy measurements indicate the existence of an uniaxial commensurate-incommensurate transition in a solid monolayer of xenon adsorbed on the (110) face of copper. The critical exponent describing the variation of the lattice constant versus chemical potential is consistent with the value ½ predicted by Pokrovsky and Talapov.

Molecular-dynamics calculations have been used to investigate the role played by anisotropic electrostatic interactions in determining the structure and dynamics of the high-temperature phase of solid KCN. Good agreement with experimental Raman, NMR, and neutron data can be achieved if it is assumed that the charge distribution of ${\mathrm{}\left(\mathrm{CN}\right)\mathrm{}}^{-}$ in the crystal corresponds to a quadrupole moment which is much smaller than that of the free ion.

The phase diagram and the critical behavior of a discrete two-dimensional model of the commensurate-incommensurate transition is determined with use of an approximate mapping onto the six-vertex model. For an uniaxial substrate the critical behavior is that of the continuum case. For a square substrate either a single first-order transition or a second-order transition followed by a first-order transition is found.

The chalcogen site in bulk glasses of Ge${\mathrm{Se}}_2$ and Ge${\mathrm{S}}_2$ has been probed via nuclear quadrupole interactions with use of ${}_{}{}^{129}{}_{}{}^{}\mathrm{Te}_{}^m{}_{}{}^{}$ impurity atoms as parent in ${}_{}{}^{129}{}_{}{}^{}\mathrm{I}$ Mössbauer emission spectroscopy. Two distinct types of chalcogen sites are observed and are shown to provide direct evidence for intrinsically broken chemical ordering in these network glasses. The composition dependence of the site parameters in pseudobinary-alloy glasses indicates the presence of characteristic large clusters rather than a continuous random network.

Very-low-field magnetization measurements on specially prepared Au-Fe alloys are reported. It was possible to follow the spontaneous magnetization through a double magnetic transition. The spontaneous magnetization appears below the Curie temperature and disappears again at a second critical temperature.

An intrinsic Shockley-type surface-state band has been found in a random substitutional CuAl(111) single-crystal alloy containing 10 at.% Al. The surface state is located at the center of the (111) two-dimensional Brillouin zone. Its energy is considerably lower than in pure Cu and depends on surface conditions. The study of the surface state shows that alloying effects are strong near the Fermi level. The Tamm-type surface state present in pure Cu(111) is absent in the alloy.

The possibility of observing atomic lines in the x-ray spectra of strongly magnetized accreting neutron stars is discussed. For magnetic field strengths ranging from ${10}^{11}$-${10}^{14}$ G, both the energies and oscillator strengths of Fe XXVI lines are calculated quantitatively. These lines are expected to be highest in energy, and should dominate at source temperatures $\mathrm{kT}\sim 10-30$ keV.

From recent developments in the area of nuclear parity nonconservation we extract evidence for (1) SU(3) /soft-pion breaking in weak pionic vertices, and (2) larger values of quark masses than have been used in previous evaluations of "penguin" matrix elements.

We report a high-statistics study of the reaction $p+\mathrm{W}\to {\mu }^{+}+{\mu }^{-}+X$ with use of an intense 400-GeV/c proton beam, a magnetized-iron beam dump, and a wide-acceptance detector. Using data near $x_{\mathrm{F}}=0\mathrm{}$, we have extracted the nucleon sea-quark distribution and find it to be a factor 1.6±0.3 larger than that obtained by inelastic charged-current neutrino scattering. We then compare the Drell-Yan prediction with our data including the previously unexplored region of large $x_{\mathrm{F}}$ and find excellent agreement for a wide range of $\mu$-pair invariant mass.

A new determination of the ${}_{}{}^{57}{}_{}{}^{}\mathrm{Fe}_{}^m{}_{}{}^{}$ quadrupole moment has yielded the value 0.082 b, which is only half of the currently accepted value. The procedure combined first-principles calculation of the field gradients at the Fe nucleus in Fe${\mathrm{Cl}}_2$ and Fe${\mathrm{Br}}_2$ molecules with published quadrupole splittings for those molecules trapped in rare-gas matrices. The field gradients are strongly influenced by iron $3p$ covalency.

We argue that the nuclear giant isovector monopole resonance should be observable with pion charge-exchange reactions (${\pi }^{-}$,${\pi }^0$) in the energy region close to the (3, 3) resonance.

The molecular dipole moment along the internuclear line is treated as a collective coordinate to describe the sharing of electrons in slow atomic collisions. With use of the constrained Hartree-Fock method, potential energy surfaces for Li-F and ${\mathrm{}(\mathrm{H}\mathrm{e}-\mathrm{H}\mathrm{e})\mathrm{}}^{2+}$ are calculated as a function of the internuclear separation and the dipole deformation. This offers a conceptual framework to view a charge-changing process as the motion along a path in the energy surface. Consequences for the molecular orbitals are discussed.

Relative bremsstrahlung cross sections have been measured for free atoms, with atomic numbers in the range $Z=2\mathrm{}$ to $Z=92\mathrm{}$, at low incident electron energies of 2.5 and 10 keV. The results agree reasonably with a theoretical calculation of Pratt et al., except at the largest $Z$ number, where differences of up to a factor of 2 at low photon energies are observed.

In this Letter we report the first observation of inelastic x-ray scattering from an atom in which both Raman and Compton processes have been observed simultaneously. It has been observed that x-ray Raman and Compton scattering in the vicinity of a deep atomic level exhibit different behavior as a function of incident photon energy.

Experimental and theoretical normal photoelectron diffraction studies of CO adsorbed on Ni are presented. It is shown for the first time that normal photoelectron diffraction can yield definitive structure determinations in molecular adsorbate systems. The linear-bonded atop geometry of $c(2\mathrm{}\times 2)$ CO- Ni(001) is confirmed, while CO is found to occupy the twofold bridge site in $(\sqrt{3}\times \sqrt{3})R30°$ CO- Ni(111).

Analysis of low-energy electron diffraction patterns for Si (111)-(7×7)H surface shows that they are consistent with a structural model of identical islands that are approximately triangular with [$\overline{11}2$] step boundaries and have area approximately half that of the 7×7 unit mesh and height within 5% of the bulk Si (111) double-layer spacing.

Generalized valence-bond calculations suggest that atomic oxygen chemisorbed on Ni(100) leads to two distinct low-lying states: (1) the radical state with $R_{\perp }=0.88\mathrm{}$ Å and ${\omega }_{\perp }=55\mathrm{}$ meV and (2) the surface oxide state with $R_{\perp }=0.26\mathrm{}$ Å and ${\omega }_{\perp }=38\mathrm{}$ meV. We suggest that the radical state dominates for $p(2\mathrm{}\times 2)$ and that the oxide state dominates for $c(2\mathrm{}\times 2)$. We find that atomic H, Cl, and S lead to only one low-lying state.

Time-resolved transmission and reflectivity of silicon on sapphire have been studied at $\lambda =1152\mathrm{} \mathrm{and} 633$ nm following excitation by a ∼1 J/${\mathrm{cm}}^2$, 8 nsec pulse at 485 nm. In addition, the spectral dependence of the transient absorption was obtained for the range 1.3 to 3.3 eV with use of a pulsed-dye-laser probe. The results are inconsistent with a metallic molten state but suggest the existence of a self-confined dense carrier system similar to that proposed by Van Vechten and Wautelet.

The low-field ac magnetic susceptibility of the amorphous (FeMn)PBAl and (FeNi)-PBAl, and the crystalline (PdFe)Mn random magnetic alloys near their critical concentrations was measured under pressure up to 20 kbar between 1 and 300 K. The results support the proposed existence of reentrant ferromagnetism, and show the important role of magnetic clustering in the magnetic behavior of these alloys.