Ab initio pseudopotential calculations of a nine-layer Rh(001) film find the surface and first subsurface layers are ferromagnetic. The calculated surface energy lies within the range of experimental estimates and the discrepancy between LEED and an earlier calculation for the surface relaxation is greatly reduced.

High q-resolution neutron-scattering measurements of the critical scattering in Tb above the magnetic-spiral phase transition temperature ${\mathit{T}}_{\mathit{s}}$ exhibit a two-component line shape, as recently documented in Ho. This implies the existence of a second length scale. By using a narrow beam only 300 μm wide, and then translating the crystal through the beam, we have established that the origin of the second length scale lies within the near surface volume or ‘‘skin’’ of the Tb crystal. This is manifested by a large enhancement of the scattering intensity at the c-axis face of the cube-shaped crystal.

The conduction electron spin resonance (CESR) of ${\mathrm{Rb}}_3$${\mathrm{C}}_{60}$ has been observed for the first time and the spin susceptibility found to be ${\mathrm{\chi }}_{\mathit{s}}$=(12.4±4)×${10}^{\mathrm{-}4}$ emu/mol, in agreement with static measurements. The CESR linewidth is anomalously large, 1300 G at 30 K giving a spin lattice relaxation rate ${\mathit{T}}_1^{\mathrm{-}1}$=9.0×${10}^{\mathrm{-}11}$ ${\sec }^{\mathrm{-}1}$, and we suggest that it is caused by large molecular disorder. The ESR line formerly assigned to ${\mathrm{Rb}}_3$${\mathrm{C}}_{60}$ arises from an unidentified nonsuperconducting phase ${\mathrm{Rb}}_{\mathit{x}}$${\mathrm{C}}_{60}$ which has a structural transition near 400 K and a thermal history dependent metal-insulator transition at lower temperatures.

Compton scattering studies, performed at the KEK accumulation ring in Japan with circularly polarized synchrotron radiation, have been used to determine the spin-dependent Compton profile of ${\mathrm{HoFe}}_2$ at temperatures between 10 and 300 K. The holmium spin moment, which is antiferromagnetically coupled to that on the Fe sites, softens as the temperature rises leading to a reversal of the net spin direciton. This has been observed directly and the spin compensation temperature has been estimated from the Compton data to be 210±10 K.

We have studied the bonding of K and Cs to Ni and Cu metal surfaces by examining the soft-x-ray emission from the K 3p and Cs 5p core holes. The localization of the core hole allows a measurement of the coverage dependence of the valence states specifically associated with the alkali atom. The energy distribution of these states shows, certainly in the case of Ni, that the substrate ${\mathit{d}}_{\mathit{z}}^2$ state plays a non-negligible role in the chemical bonding. Further for Ni, the quasi-two-dimensional metalization of the alkali overlayers was clearly observed.

Two-variable model equations that capture some essential dynamical features of quantitative electrophysiological models of cardiac tissue are introduced. In one dimension, these equations naturally reproduce an experimentally observed oscillatory pulse instability that causes an alternation in action potential duration. In two dimensions, spontaneous spiral breakup leading to a spatially disorganized electrical wave activity is shown to occur as a direct consequence of this instability.

We analyze here a new mechanism leading to the spontaneous generation of endogenous ionic currents flowing in growing cells. The mechanism, based on the sensitivity of channels and pumps to membrane potential and ionic concentrations, leads to a linear instability of the uniform resting state. Ions may further or prevent the ionic currents to flow depending on the properties of the relevant pump or channel associated to them. For instance, a calcium ion can be responsible for the observed ionic disturbances. First, it contributes to favor nonuniform ionic disturbances with a wavelength of the same order of magnitude as a typical cell diameter. Second, it has the property to diffuse much more slowly in the cytoplasm than in an ordinary liquid because of the presence of negatively charged ligands. As a result, the time scale of the development of the instability in a cell of 100 μm diameter is some hours in agreement with experiments

The behavior of self-avoiding fluid vesicles in elongational flow is studied using Monte Carlo simulations and scaling arguments. The simulations are carried out for membranes with a very small bending rigidity, in the free-draining approximation. We find that there is a gradual crossover from self-avoiding branched-polymer to elongated linear-polymer behavior as the flow rate is increased. At small flow rates, our results scale with the relaxation time of undisturbed branched polymers. The scaling behavior is the same in both unidirectional and planar flow geometries.

We consider theories with late-time phase transitions that lead to the formation of energetically soft domain wall effects. These transitions occur in the vacuum state of a weakly coupled scalar field which is not in thermal equilibrium. The spatial properties and distribution of these domain walls are computed using percolation theory. Assuming spherical collapse of matter, the percolation results are used to accurately predict the richness distribution of Abell clusters.

We investigate the thermal equilibrium properties of kinks in a classical ${\mathrm{\phi }}^4$ field theory in 1+1 dimensions. The distribution function, kink density, and correlation function are determined from large scale simulations. A dilute gas description of kinks is shown to be valid below a characteristic temperature. A double Gaussian approximation to evaluate the eigenvalues of the transfer operator enables us to extend the theoretical analysis to higher temperatures where the dilute gas apparoximation fails. This approach accurately predicts the temperature at which the kink description breaks down.

The spin structure function of the neutron ${\mathit{g}}_1^{\mathit{n}}$ has been determined over the range 0.03<x<0.6 at an average ${\mathit{Q}}^2$ of 2 (GeV/c${)}^2$ by measuring the asymmetry in deep inelastic scattering of polarized electrons from a polarized ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ target at energies between 19 and 26 GeV. The integral of the neutron spin structure function is found to be ${\mathcal{F}}_0^1$${\mathit{g}}_1^{\mathit{n}}$(x)dx=-0.022±0.011. Earlier reported proton results together with the Bjorken sum rule predict ${\mathcal{F}}_0^1$${\mathit{g}}_1^{\mathit{n}}$(x)dx=-0.059±0.019.

We present data on collective flow of neutrons in collisons of ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$ + ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$ at 400 MeV/nucleon. The azimuthal distribution about the beam axis is investigated with respect to the reaction plane as determined from light charged particles. The ‘‘squeezeout’’ of neutrons, perpendicular to the reaction plane, is observed for the first time. Quantitative agreement to a high level of accuracy is found between the behavior of neutrons and hydrogen ions.

One- and two-step Coulomb excitation cross sections of the double-phonon giant dipole resonance are calculated in a semiclassical formalism. The contribution of nuclear interaction is shown to be small. The multipole sum rules are used to evaluate corresponding nuclear matrix elements; the widths of final and intermediate states are taken into account. The recent experimental data re discussed and compared to our calculations.

The four-nucleon Yakubovsky equations are solved precisely for various realistic NN interactions. The resulting binding energies underbind the α particle by about 1 to 5 MeV. The one-boson-exchange NN potentials with smallest deuteron d-state probabilities provide the strongest binding. Within the group of NN-force models used the 3N and 4N binding energies are strongly correlated. The probabilities to find two nucleons at a distance r are compared to each other in the deuteron, the triton, and the α particle.

Nuclear resonance fluorescence experiments are reported to search for enhanced M1 scissors mode states in the deformed odd-mass nucleus ${}_{}{}^{163}{}_{}{}^{}\mathrm{Dy}$. A concentration of dipole strengths near 3 MeV excitation energy is found, which fits nicely into the systematics observed for M1 excitations in the neighboring even-even Dy isotopes. The observed strength distribution and the decay branching ratios are discussed in the context of the interacting boson-fermion model.

The magnetic vibrational circular dichroism (MVCD) spectra of the E-symmetry, ${\nu }_4$ modes of ${\mathrm{HCCl}}_3$, ${\mathrm{HCBr}}_3$, ${\mathrm{HCI}}_3$, and ${\mathrm{DCCl}}_3$ are presented. In each case, an MVCD A term indicating a first order vibrational Zeeman effect is observed. The vibrational g values for the ${\nu }_4$ mode of these haloforms were determined for the first time by moment analysis of the MVCD and absorption spectra. A partially charged ‘‘elastic bar’’ model is proposed to qualitatively explain the observed MVCD A terms.

A technique of two-dimensional photoelectron spectroscopy has been applied for measuring spin-orbit decay routes of the H,I,I’,I’’, and J autoionization states to the two spin-orbit components of the ground state of molecular oxygen. Strong selectivity of the spin-orbit decay routes was found. THe observed selectivity is exaplined in terms of a model in which the orbital angular momentum along the internuclear axis of the positive ion core remains unchanged during the autoionization process.

Angle-resolved high-resolution C(KVV) Auger spectra of CO were taken in the vicinity of the C(1s) ${\mathrm{\sigma }}^{\mathrm{*}}$ shape resonance. These spectra show clear evidence for the theoretically predicted anisotropic K-shell Auger emission in molecules. Complementary results from angle-resolved photoion spectroscopy show that the small size of the observed effect is, besides the varying intrinsic anisotropy of the Auger decay, also due to a smaller anisotropy in the primary absorption process than originally predicted but in good agreement with more recent calculations. Contrary to this, satellite Auger transitions show unexpectedly large anisotropies.

The orientation parameter, 〈${\mathit{J}}_{\mathit{y}}$〉/J(J+1), of the ${}_{}{}^2{}_{}{}^{}$${\mathit{F}}_{7/2}$ state of ${\mathrm{Ar}}^{+}$, formed in the two-electron process ${\mathrm{He}}^{+}$+Ar→He(1${\mathit{s}}^2$)+${\mathrm{Ar}}^{+}$(3${\mathit{p}}^4$4p${,}^2$${\mathit{F}}_{7/2}$) has been measured at various scattering angles. The measured value of 〈${\mathit{J}}_{\mathit{y}}$〉, the component of the total angular momentum perpendicular to the collision plane, is interpreted as resulting from a collective circulation of the inactive 3${\mathit{p}}^4$ core electrons as well as the active 4p electron. We find that over the range of scattering angles studied, this collective-electron circulation is in the direction of the rotating internuclear axis, the direction given by the propensity rule, suggesting that this rule is more general than heretofore proposed.

We discuss a novel laser scheme in which N three-level atoms maintain full cooperativity in a stationary regime. The intensity I of radiation is proportional to ${\mathit{N}}^2$, the linewidth scales as 1/${\mathit{N}}^2$, and the output intensity fluctuations display up to 100% squeezing at low frequencies. The possibility of simultaneously slowing down phase diffusion and reducing intensity fluctuations makes this kind of laser an attractive goal to go for.