Ion-enhanced processes on a solid surface

The results of studies performed by the authors in the field of ion enhancement of various processes on the solid surface were generalized. The effect of ion irradiation on the kinetics of elementary processes during thin film formation was analyzed. Systematic features of ion enhancement of film formation on a metal and ionic crystal surface were studied. The effect of ion enhancement of epitaxy on the ionic crystal surface was revealed and the observed features were explained. An important role of inelastic ion-atom interactions in the effect of ion enhancement of surface processes was shown, and their features were investigated. It was found that the efficiency of ion enhancement on the ionic crystal surface under conditions of inelastic interactions can be increased by one or two orders of magnitude in comparison with the yield of elastic processes. Inelastic ion-atom interactions at low ion energies occur in selective energy ranges, nonmonotonically depend on the current density, and require a selective approach to the choice of the ion type and ion irradiation parameters.     

Curvature-dependent surface tension of a growing droplet

A ghost interface simulation technique is developed and applied to supersaturated Lennard-Jones liquid-vapor interfaces. It is shown that the surface tension decreases approximately linearly with the supersaturation ratio and that it vanishes at the spinodal. The effect leads to a curvature-dependent surface tension since, it is argued, the local supersaturation of the vapor above a droplet is greater than in the bulk due to slow diffusion in the vapor phase. An analytic approximation is given for the local supersaturation ratio, and an analytic expression for this contribution to Tolman's length is derived. The theory gives a smaller critical radius and reduces the free energy barrier to nucleation compared to classical homogeneous nucleation theory, which have important implications for the kinetics of droplet and bubble formation.     

Liquid rope coiling on a solid surface

We present an experimental study of the coiling instability of a liquid "rope" falling on a solid surface. Coiling can occur in three different regimes--viscous, gravitational, or inertial--depending on the fluid viscosity and density, the fall height, and the flow rate. The competition among the different forces causes the coiling frequency first to decrease and subsequently to increase with increasing height. We also observe an oscillation between two coiling states in the gravitational-to-inertial transitional range, reflecting the multivaluedness of the dependence of coiling frequency on fall height. The data can be rescaled in a universal way, and agree very well with numerically predicted coiling frequencies.     

Twist of growing bacterial colonies

Twist observed in growing bacterial colonies at the macrolevel is explained in terms of the self-assembly (self-organization) of film-forming protein clusters, since the in vitro and in vivo behavior and symmetry properties of protein in an open thermodynamically nonequilibrium system are identical. The self-assembly of elastic protein films in the course of condensation in the protein-water system obeys the laws of the elasticity theory. As the viscosity of the system grows, the transition of the protein from the liquid-crystal to the solid phase occurs. This transition has a nonlinear dynamics, which also shows up at the macrolevel. Opposite vorticities (twist) appear in the system. Such a modification of protein has been named protos. It is hypothesized that the formation of an elastic nonequilibrium protos film is consistent with the behavior and orientation of elastic forces and magnetic fields in the presence of unlike electric charges.     

Reflectivity of a shocked solid surface

Using a one-dimensional hydrodynamic code and a post-processor which treats the propagation of an electromagnetic wave in an inhomogeneous plasma, we have studied the reflectivity of a shocked solid surface. The simulations were used to assess the diagnostic value of such measurements in determining the electrical conductivity of a dense plasma. Results of the calculations were also compared with recent measurements on the rear surface reflectivity of a laser-irradiated foil. This suggested that the conductivity used in the present simulations was overestimated.     

Photostimulated diffusion of atoms adsorbed on a solid surface

A new light-induced effect—surface photodiffusion—is found in the processes of transfer on a solid surface. The essence of the effect is that the energy of electronic excitation of an adsorbed atom is transformed into that of its motion over the surface. It is shown that, under nonuniform illumination of the surface, the adsorbed atoms are moved away from the illuminated region, with the atomic concentration at the boundary between the illuminated and dark regions exceeding the equilibrium value. The dark and photoinduced diffusion coefficients are measured, and the value of the diffusion barrier height is estimated.     

Chiral surface plasmon polaritons on metallic nanowires

Chiral surface plasmon polaritons (SPPs) can be generated by linearly polarized light incident at the end of a nanowire, exciting a coherent superposition of three specific nanowire waveguide modes. Images of chiral SPPs on individual nanowires obtained from quantum dot fluorescence excited by the SPP evanescent field reveal the chirality predicted in our theoretical model. The handedness and spatial extent of the helical periods of the chiral SPPs depend on the input polarization angle and nanowire diameter as well as the dielectric environment. Chirality is preserved in the free-space output wave, making a metallic nanowire a broad bandwidth subwavelength source of circular polarized photons.     

Antiproton reflection by a solid surface

The AE?IS experiment (Antimatter Experiment: Gravity, Interferometry, Spectroscopy (Drobychev et al., 2007)), aims at directly measuring the gravitational acceleration g on a beam of cold antihydrogen ( $\overline{\rm H}$ ). After production, the $\overline{\rm H}$ atoms will be driven to fly horizontally with a velocity of a few 100 m/s for a path length of about 1 meter. The small deflection, few tens of μm, will be measured using two material gratings coupled to a position-sensitive detector working as a Moiré deflectometer similarly to what has been done with atoms (Oberthaler et al., Phys Rev A 54:3165, 1996). Details about the detection of the $\overline{\rm H}$ annihilation point at the end of the flight path with a position-sensitive microstrip detector and a silicon tracker system will be discussed.     

Quasi-steady-state surface acoustic waves at a rough solid surface

Sound propagation along an inhomogeneous solid-vacuum interface is considered. The frequency-wavenumber relation has been obtained for the transverse-polarized surface wave and the range of existence of this wave has been analyzed. The surface roughness is shown to produce additional damping.     

Impingement of a vortex ring transporting admixture on a solid surface

Normal impingement of a vortex ring, formed in water and transporting the coloring admixture, on a solid surface was studied experimentally. The size and shape of a trace of vortex impingement on the surface were determined. It was found that the size of trace does not depend on the speed of the vortex ring, and its shape is determined by the amount of admixture in the vortex. The connection of results with possible mechanism of annular structures formation on the ice of Lake Baikal is discussed.     

Elastic interaction of two atoms adsorbed on a solid surface

The long-range interaction of two adsorbed atoms mediated by the elastic distortion of the substrate is calculated classically for an elastically isotropic substrate. For identical atoms, the interaction is repulsive; for different atoms, it can be repulsive or attractive. It varies as ρ^?3 with the distance ρ between the two adsorbed atoms. This is the same spatial dependence as for the dipole - dipole interaction between two adsorbed atoms. For two xenon atoms adsorbed on gold, the elastic interaction is somewhat smaller than the dipole-dipole interaction. The interaction energy is inversely proportional to the shear modulus of the substrate, so that it may become quite large near a distortive phase transition.     

Mechanisms and dynamics of protein clustering on a solid surface

A methodology for discovering the mechanisms and dynamics of protein clustering on solid surfaces is presented. In situ atomic force microscopy images are quantitatively compared to Monte Carlo simulations using cluster statistics to differentiate various models. We study lysozyme adsorption on mica as a model system and find that all surface-supported clusters are mobile, not just the monomers, with diffusion constant inversely related to cluster size. The surface monomer diffusion constant is measured to be D(1) approximately 9 x 10(-16) cm(2) s(-1), such a low value being difficult to measure using other techniques.     

Chiral fermions on a compact Riemann surface: A sheaf cohomology analysis

We prove that the correlation functions of a system of chiral fermions on a compact Riemann surface are determined by postulating their behaviour at coincident points and a principle of maximal analyticity. The proof proceeds by a reformulation as a problem of sheaf cohomology. Wick's theorem and the Fay identities are rigorous consequences of our analysis.     

Thermodynamic and mechanical equilibrium morphologies of microasperities on a solid surface

Micron size tapered asperities having a bent or spiralled appearance have been observed in SEM studies of ion bombarded surfaces. We suggest that these forms arise from the relaxation of surface stress σ on what are initially conical asperities. The relaxation process could lead to the adoption of asperity forms which correspond to the well-known catenoidal and helicoidal minimal surfaces of differential geometry.