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An analytical solution is developed for thermal stress in exponentially time decaying laser short-pulse heating of a metallic surface. Because the heating duration is short, a nonequilibrium heating model incorporating the electron kinetic theory approach is used to formulate the temperature distribution during the laser heating pulse. Thermomechanical coupling is introduced in the analysis to formulate the thermal stress field. Thermodynamic irreversibility is considered and the entropy generation rate due to heat transfer and thermal stress field is formulated during the heating process. It is found that temperature decays gradually in the surface region and becomes sharp as the distance increases towards the solid bulk. Thermal stress is compressive in the irradiated region. Thermodynamic irreversibility due to heat transfer dominates thermodynamic irreversibility because of the thermal stress field. PACS No.: 44.10.+i. Nous presentons une solution analytique pour la contrainte thermique due a une impulsion laser a decroissance exponentielle sur une surface metallique. Parce que le chauffage est de courte duree, nous utilisons un modele de chauffage hors d'equilibre incorporant la theorie cinetique des electrons afin de formuler la distribution de temperature pendant l'impulsion laser. L'introduction d'un couplage thermomecanique permet de decrire le champ de contrainte thermique. Nous tenons compte de l'irreversibilite thermodynamique et nous formulons le taux de generation d'entropie du au transfert de chaleur et au champ de contrainte thermique pendant le processus, pour trouver que la diminution de temperature qui est graduelle dans la region du chauffage devient rapide a distance. La contrainte thermique est compressive dans la region du chauffage. L'irreversibilite thermodynamique due au transfert de chaleur est plus importante que celle due a la contrainte thermique. [Traduit par la Redaction], Introduction Laser short pulse heating of metallic surfaces involves nonequilibrium energy transport in the irradiated region. Electron and lattice subsystems separate thermally because of electron temperature increases through energy absorption [...]

We analyze the focusing properties of Fresnel zone plates fabricated over steel tapes using laser ablation. Our intention is to implement the use of micro-optical elements when the use of conventional chrome-glass elements is not indicated. Because of the manufacture process, the surface presents a certain anisotropic roughness, which reduces the focusing properties. First, we develop numerical simulations by means of the Rayleigh--Sommerfeld approach, showing how roughness in both levels of the Fresnel zone plate affects the focalization of the lens. We also manufacture Fresnel zone plates over steel tape, and perform experimental verification that corroborates the numerical results. [c] 2010 Optical Society of America OCIS codes: 050.1965, 240.3990, 240.5770.

Nonadiabatic coupling of nuclear motion to electronic excitations at metal surfaces is believed to influence a host of important chemical processes and has generated a great deal of experimental and theoretical interest. We applied a recently developed theoretical framework to examine the nature and importance of nonadiabatic behavior in a system that has been extensively studied experimentally: the scattering of vibrationally excited nitric oxide molecules from a Au(111) surface. We conclude that the nonadiabatic transition rate depends strongly on both the N-O internuclear separation and the molecular orientation and, furthermore, that molecule-surface forces can steer the molecule into strong-coupling configurations. This mechanism elucidates key features of the experiments and provides several testable predictions regarding the dependence of vibrational energy transfer on the initial vibrational energy, molecular orientation, and incident angle. 10.1126/science.1179240

A chemicurrent is a flux of fast (kinetic energy [??] 0.5-1.3 eV) metal electrons caused by moderately exothermic (1-3 eV) chemical reactions over high work function (4-6 eV) metal surfaces. In this report, the relation between chemicurrent and surface chemistry is elucidated with a combination of top-down phenomenology and bottom-up atomic-scale modeling. Examination of catalytic CO oxidation, an example which exhibits a chemicurrent, reveals 3 constituents of this relation: The localization of some conduction electrons to the surface via a reduction reaction, 0.5 [O.sub.2] + [delta][e.sup.-] [right arrow] [O.sup.[delta]-] (Red); the delocalization of some surface electrons into a conduction band in an oxidation reaction, [O.sup.[delta]-] + CO [right arrow] C[O.sup.[delta]-.sub.2] [right arrow] C[O.sub.2] + [[delta]e.sup.-] (Ox); and relaxation without charge transfer (Rel). Juxtaposition of Red, Ox, and Rel produces a daunting variety of metal electronic excitations, but only those that originate from C[O.sub.2] reactive desorption are long-range and fast enough to dominate the chemicurrent. The chemicurrent yield depends on the universality class of the desorption process and the distribution of the desorption thresholds. This analysis implies a power-law relation with exponent 2.66 between the chemicurrent and the heat of adsorption, which is consistent with experimental findings for a range of systems. This picture also applies to other oxidation-reduction reactions over high work function metal surfaces. heterogeneous catalysis | hot electrons | metal surfaces | surface science | transition metals

The effect of facial ring jewelry is investigated on the energy absorbed in the head when illuminated by communications-enabled personal data assistant (PDA)-type devices. We study the relative changes in specific absorption rates in the head due to perturbing metallic rings in proximity to the face illuminated by a 1.8 GHz dipole and a monopole on a conducting box. Simple and complex head models used in a validated finite-difference time-domain (FDTD) simulation are compared with measurements from an industry standard DASY4 SAR measurement system. Both simulation and measurement ate referred to the IEEE specific anthropomorphic mannequin head. Results show that metallic rings may alter specific absorption rates (SAR) level distributions within the head. Results are given for several common ring sizes. Index Terms--DASY4, finite-difference time-domain (FDTD), metallic jewelry, personal data assistant (PDA), specific absorption rates (SAR).

A method to detect minute flaws on metal parts is proposed to remove defective parts before assembling in a factory. The input grayscale images of metal parts are directly used to recognize flaws without any image conversion to shorten recognition time. The recognition problem to find flaws and detect their position on the metal parts is converted to another problem that searches for the maximum peak and the variables producing the peak. Then, the recognition problem can be treated as an optimization problem, and this conversion allows us to utilize high genetic algorithm performances in optimization. The effectiveness and problems of the proposed method are studied on the standing points of recognition speed and quantitative recognition ability. Based on the analysis, we furthermore improved our system to increase the flaw detection rate; the lighting direction was changed to find the best lighting condition that can emphasize the contrast between the metal surface and the flaw by using the reflection character of the hairline on the metal, which is resulted by a polishing process. Index Terms--Genetic algorithm (GA), metal surface inspection, model-based matching.

The major limiting factor in the transmission of high-power microwave (HPM) has been the interface between dielectric-vacuum or, even more severely, between dielectric-air, if HPM is to be radiated into the atmosphere. Extensive studies have identified the physical mechanisms associated with vacuum-dielectric flashover, as opposed to the mechanisms associated with air-dielectric flashover, which are not as well known. Surface-flashover tests involving high field enhancement due to the presence of a triple point have shown that volume breakdown threshold (dielectric removed) is approximately 50% higher than the flashover threshold with a dielectric interface over the 90-760 torr range. In order to quantify the role of field enhancement in the flashover process independent of electron injection from metallic surfaces, the effects of the triple point are minimized by carefully choosing the geometry, and in some cases, the triple point is 'removed' from the flashover location. Experimental results were presented, including the impact of gas pressure and the presence of UV illumination, along with temperature analysis of the developing discharge plasma and temporally resolved images of the flashover formation. These results are compared with literature data for volume breakdown in air, with discussion on the similarities and differences between the data. Index Terms--Atmospheric, breakdown, dielectric surface, high-power microwave (HPM), surface flashover.

In the field of industrial vision, the three-dimensional inspection of highly reflective metallic objects is still a delicate task. We deal with a new automated three-dimensional inspection system based on polarization analysis. We first present an extension of the shape-from-polarization method for dielectric surfaces to metallic surfaces. Then, we describe what we believe to be a new way of solving the ambiguity concerning the normal orientation with an active lighting system. Finally, applications to shape-defect detection are discussed, and the efficiency of the system to discriminate defects on specular metallic objects made by stamping and polishing is presented. OCIS code: 110.6880

A new conformal finite-difference time-domain (CFDTD) updating scheme for metallic surfaces nonaligned in the grid is presented in this paper. In contrast to existing conformal models, the new model can be formulated with the original Yee FDTD update equation. Therefore, the proposed scheme can be easily added in standard FDTD codes even if the codes are already parallelized or hardware-accelerated. In addition, based on the commonly used conventional stability criterion, a derivation of the stability is presented and based on the conformal geometric information, a time step reduction formula is presented. The time step reduction is used as a user-defined parameter to tradeoff speed versus accuracy. The achievable geometric precision is optimized to a given time step. Therefore, even with the conventional time step (no reduction) the presented scheme profits from the conformal discretization. To show the performance and the robustness of the proposed scheme canonical validations and two real world applications were investigated. A broadband low profile (circular) antenna was successfully simulated showing the benefit of the conformal FDTD method compared to the conventional scheme. Furthermore, a CAD based mobile phone was conformally discretized and successfully simulated showing that the proposed scheme is highly suited for the simulation of advanced engineering problems. Index Terms--Conformal finite-difference time-domain (CFDTD) method, finite-difference time-domain (FDTD) method, subcell.

Recently, there has been an increased interest in the problem of wave transmission through sub-wavelength apertures, following successful experimental demonstration by several groups for enhancing optical power transmission through nano-scale holes in metallic screens due to properly designed periodic corrugation. Oliner, Jackson, and their co-workers explained and justified this phenomenon as the result of the excitation of the leaky waves supported by the corrugated screen. Here we discuss in detail the mechanism and analysis for another setup we have recently proposed, in which metamaterial layers with special parameters may be utilized as covers over a single sub-wavelength aperture in a perfectly electric conducting (PEC) flat screen in order to increase the wave transmission through this aperture, and we provide a detailed physical insights and analytical explanation for this aperture setup that may lead to similar, potentially even more pronounced effects when the proper metamaterial layers are used in the entrance and the exit face of the hole in the flat PEC screen with no corrugation. Some numerical results confirming this theory are presented and discussed. We also investigate the sensitivity of the transmission enhancement to the geometrical and electromagnetic parameters of this structure. Index Terms--Aperture coupling, aperture enhancement, leaky wave, metamaterials, polariton, sub-wavelength aperture.

We use the finite-difference time-domain (FDTD) method to model the spectral properties of frequency-selective surfaces (FSSs) at normal incidence in the 1-10 [micro]m wavelength. At these wavelengths the usual assumption that the metallic portions of a FSS are infinitesimally thin perfect conductors are no longer valid. We include the effects of dispersive complex conductivity for real metals and dispersive permittivity for dielectric materials by developing a unified approach that is especially suited for use in FDTD simulations. We concentrate on the finite nature of the metallic conductivity and its variation with wavelength in FSS structures. Our simulation results indicate that the resonant spectrum of a FSS in this wavelength range depends not only on the geometry of the structure and the dielectric substrate present, but also critically on the dispersive properties of the metal species used for the conductors. OCIS codes: 000.4430, 160.3900, 160.4760, 260.2030, 260.3910.

We present a procedure that compensates for phase aberrations in digital holographic microscopy by computing a polynomial phase mask directly from the hologram. The phase-mask parameters are computed automatically without knowledge of physical values such as wave vectors, focal lengths, or distances. This method enables one to reconstruct correct and accurate phase distributions, even in the presence of strong and high-order aberrations. Examples of applications are shown for microlens imaging and for compensating for the deformations associated with a tilted thick plate. Finally we show that this method allows compensation for the curvature of the specimen, revealing its surface defects and roughness. Examples of applications are shown for microlenses and metallic sphere imaging. OCIS codes: 090.1760, 090.1000, 180.0180, 120.5050, 120.3620.

A density matrix treatment is presented for the vibrational relaxation of the frustrated translational mode of a molecule adsorbed on a metal system. The system is modeled as a vibrating adsorbate oscillator coupled to a bath of harmonic oscillators representing either phonons or electronic density fluctuations.

The electronic structure, adsorption and bonding of two isomer molecules, orthocarborane and metacarborane are compared. Significant differences in the experimental binding energies are noticed

Spontaneous polymerization (S-Poly) is a novel process to form protective polymer coatings on aluminum and other metals. Here we discuss polymerization and coating properties when two fluorinated monomers are introduced into the S-Poly system. The resulting coatings were characterized using attenuated total reflectance fourier transform infrared (ATR-FTIR), differential scanning calorimetry (DSC), optical microscope and other measurements. Fluorinated coatings showed excellent dielectric properties and strong hydrophobicity. Their dry adhesion strength was a little lower than the coatings in previous systems, but changed very little after immersion in hot water for several days. Some of the fluorinated coatings exhibited significantly improved corrosion resistance in most corrosion tests., Zheng, Haipeng (*) Guy D. Davis (+) James P. Bell (*) INTRODUCTION Coatings on metal surfaces are widely used in applications ranging from macro equipment to microelectronics devices. Among many [...]

The possibility of quantum control of surface photochemical reaction was demonstrated for the system of Cs/Cu(III). The report stated that the phase dependence of two-photon photoemission spectra demonstrated the control of desorptive motion of Cs atoms.

Research investigates spectra of the small molecules adsorbed onto single-crystal metal surfaces obtained under ultra-high vacuum using reflection absorption infrared spectroscopy. Instrumentation details and data on molecular structure ranging from qualitative to ab initio electronic structure determination of chemisorbed molecules are discussed.

A discussion on the dynamic processes occurring at metal surfaces in terms of theory and experimental approach is presented. The review covers a wide range of topics from inelasticitic-molecule-surface scattering to electron-induced dynamics at metal surfaces. Phonon and electron-hole pair dissipation with reference to adsorbate dynamics is discussed.

The changes in the microtopography of a metal surface during a corrosion process are measured by decorrelation of the scattered speckle fields under coherent illumination. For that purpose a quantitative relation between the decorrelation of the scattered light fields and the rate of corrosion is established in a theoretical model, based on the statistics of phase and reflectivity changes of point scatterers at the surface. The speckle fields are recorded by a CCD camera and processed numerically in a computer, yielding the standard deviation of the topography changes with nanometer sensitivity. From the analysis of a series of images taken at equal time intervals during the corrosion process, the degree of interrelation among subsequent topography changes is calculated.

A study was conducted relating to research on the nature and occurrence of copper surface oxidation in aqueous solution-related ambient environments. Surface enhanced Raman spectroscopy was used to probe the surface structural changes linked to potential dependent oxidation and reduction of copper in alkaline, neutral and acidic media. Experimental methodology, findings and implications are discussed. Results are also compared with evidence derived from previous experiments which confirm adsorbed oxygen on copper electrodes.

The current status of transition metal cluster surface characteristics as influenced by size effects is presented. Determination of metal cluster structures and reactivity of bimetallic clusters are addressed.

Micropatterning as a method of controlling surface properties has applications in many fields, including electronics and cell biology. A new and simple way to pattern microscopic surface structures uses self-assembled monolayers deposited on topographic islands on a metal surface. The study shows that disorder is greater at the step edges, creating fine-scale surface-energy inhomogenities that can be selectively etched.

Synchrotron-based high-resolution photoemission was used to analyze adsorption and dissociation of H2S and S2 on a series of oxide and metal/oxide surfaces. H2S and S2 generally interact with the metal centers of oxides. At 300 K, H2S undergoes total decomposition. The rate of decomposition on Al2O3 is much lower than those observed on Cr3O4, Cr2O3, ZnO and Cu2O. For these systems, the smaller the band gap in the oxide, the bigger its reactivity toward S-containing molecules. The use of ab initio self-consistent-field calculations and a model that unifies perturbation theory with Huckel and tight-binding approach are discussed.

The metal/electrolyte interface is analyzed by employing jellium model for metal surfaces and Bethe approximation for dipolar interactions. The total surface energy considering the metal-solvent interactions is then calculated using a one-parameter family of trial functions for the electronic density profile. A systematic analysis of the metal-solvent bond length and its dependence on electrode charge density is presented. The results are discussed.

The paper presents a method of the evaluation of capacitance of paraboloidal and spherical bowl using the method of moments based on pulse function as the basis function and point matching for testing. The analysis is carried out on dividing the surface into curvilinear rectangular and triangular subsections. Numerical data on capacitance are presented. Index Terms - Capacitance evaluation, isolated paraboloidal bowl, moment method, sperical bowl.

Numerical methods, based on the finite element alternating method, are used to study the effectiveness of repairs of metal structures using composite patches. The results from 15 different specimens are compared with Denney's experimental data. Additionally, a numerical analysis of the effect of low-stress high-temperature and high-stress low-temperature cycles is presented. The studies show that metals undergoing thermal-fatigue cycles are more likely to disbond than specimens undergoing constant temperature fatigue-cycles.

A new model was developed for the calculation of the nonlinear polarization and the intensity of the second harmonic radiation in the case of the metallic surfaces. The radiation is a result of two currents, one from the rapid variation of the normal component of the oscillating electric field and one from the action of the Lorentz force on conduction electrons. An accurate calculation of these currents was shown possible if adiabatic and Thomas-Ferni assumptions were considered.

Excimer-laser-induced ablation has been used to produce surface structuring of various metals. Such structuring contributed to a 5-15% enhancement of the bonding strength of these metals when a commercial adhesive was used.

ABSTRACT: This paper discusses the transmitting capacity of the so-called surface or metal contact joints by which the compressive stresses are transmitted through the directly contacting surface of steel plates. The imperfections of the contacted surface are modeled by the cylindrical and periodical sinusoidal form, and the stress distribution up to the yield state is simulated using the finite element method as a contact problem. The yielded portion of the plate spreads in the relatively small portion close to the surface, and the longitudinal displacements are not so large in this state. Therefore, the contact joint can transmit compressive loads of almost the full plastic capacity. The stress sharing with the splice plate is also evaluated by a simple spring model associated with the roughness of the contact joint, and is closely related to the bolt pitch. Therefore, the maximum tolerance for the gaps should be determined by the tolerable deformation of the contact joints and the requirements for the combined bolted joints as a total system.

Auger electron spectroscopic studies of the concentrations of sulfur in OFHC copper show that at concentrations around 10 a/o, the contact resistance values increase. Exposure of the sample to air leads to disappearance of sulfur and formation of an oxide film that enhances the contact resistance. Depending on the quantity of cold work done on the specimen, the thermal kinetics of sulfur segregation varies.

In this study the effects of intense excimer laser irradiation (10 to the eighth power-10 to the ninth power W cm to the -2) on some radiative properties of copper, aluminum, magnesium, tantalum, and molybdenum are investigated. The short pulse duration of the excimer laser (30 ns FWHM) and the wavelength of the radiation initiate a processing regime that is dominated by the effects of a laser-supported plasma above the workpiece surface. A laser- supported detonation wave is observed that acts on a thin molten surface layer. The resultant structure that is frozen on the surface is dependent on the thermophysical properties of the metal and the number and manner in which multiple pulses are applied to the surface. This surface roughness has features on both the macro- and microscopic scale that affect the radiative properties of the surface. The surface plasma also initiates very fast reaction rates that can create a thick oxidized layer on the metal surface. The surface oxide layer may either be lightly (CuO particles on a copper substrate) or tightly adhered (Al2O3 on aluminum) to the surface. The effect of excimer laser irradiation is characterized with scanning electron microscopy and Fourier transform infrared spectroscopy. Data on solar absorptivity Alpha(sub s), spectral reflectivity Rho prime(Lambda), bidirectional reflectivity Rho double prime(Lambda), and total near-normal total emissivity Epsilon prime(Tau) are also presented that show that in some cases heavily irradiated samples simulate the radiative behavior of a flat absorber.

The formation of a surface metal-metal bond can produce large perturbations in the electronic, chemical, and catalytic properties of a metal. Recent studies indicate that charge transfer is an important component in surface metal-metal bonds that involve dissimilar elements. The larger the charge transfer, the stronger the cohesive energy of the bimetallic bond. On a surface, the formation of a heteronuclear metal-metal bond induces a flow of electron density toward the element with the larger fraction of empty states in its valence band. This behavior is completely contrary to that observed in bulk alloys, indicating that the nature of a heteronuclear metal-metal bond depends strongly on the structural geometry of the bimetallic system., In general, metals are elements characterized by the presence of a large number of valence orbitals that can donate or accept electrons. Isolated metal atoms are unstable, very reactive, and [...]

Author(s): Bogdan Diaconescu [1]; Karsten Pohl (corresponding author) [1]; Luca Vattuone [2]; Letizia Savio [2]; Philip Hofmann [3]; Vyacheslav M. Silkin [4]; Jose M. Pitarke [5]; Eugene V. Chulkov [4]; [...]

We have studied the morphology, structure and magnetism of Fe films thermally deposited on stepped Cu(111) by scanning tunnelling microscopy (STM), low energy electron diffraction (LEED) and magneto-optical Kerr effect (MOKE). At room temperature, in the submonolayer range Fe films grow as quasi one-dimensional stripes along the upper step edges due to a strong decoration effect. Between 1.4 and 1.8 monolayer coverage the stripes percolate and become two-dimensional films. Between 2.3 and 2.7 monolayer coverage the films undergo a structural transition from fcc(111) to bcc(110) with Kurdjumov-Sachs orientation. In the fcc range the films have a low net magnetic moment, and a perpendicular easy magnetization axis. The magnetization switches to an in-plane high-moment phase correlated with the fcc to bcc structural transformation. Index Terms - Stepped metal surfaces, ultra thin film growth and magnetism

Interaction of high-power laser light with materials often causes irreversible damage of the near-surface region. It is shown that copper single-crystal surfaces can be patterned by laser light. Irradiation with green light produced adatoms and vacancies, which self-organized into nanoscale pyramids. This restructuring can be removed by annealing. In contrast to green light, infrared laser irradiation at equivalent absorbed energy density did not produce any structural change. This, for metallic systems, unforeseen spectral difference in laser light action points to a concerted process as the source for structural modification, which involves long-lived primary excitation of localized d-electrons through interband transition together with phonon excitation., The creation and dissipation of electronic excitation are fundamental for a variety of physical and chemical processes. Lasers, as a source of primary excitation, play an expanding role in material [...]

Time-resolved two-photon photoemission in combination with the coherent excitation of several quantum states was used to study the ultrafast electron dynamics of image-potential states on metal surfaces. For a (100) surface of copper, the spectroscopy of quantum beats made previously unresolved high-order states (quantum number n [is greater than or equal to] 4) experimentally accessible. By exciting electrons close to the vacuum level, electron wave packets could be created and detected that described the quasi-classical periodic motion of weakly bound electrons. They traveled more than 200 A away from the surface and oscillated back and forth with a period of 800 femtoseconds., Photoelectron spectroscopy has developed into one of the most versatile and successful tools for surface studies. Particularly attractive features of this technique are the high surface sensitivity associated with the [...]

A study was conducted to assess the validity of a simple sharp-kink approximation which relates the contact angle of a liquid on a surface to its density, its surface tension, and the effective molecule-surface potential. The equation might be applied to study the temperature-dependence of the contact angle for helium or alkali metal surfaces.

A systematic density functional theory (DFT) of hydrogen adsorption on Fe(111) at various coverages is presented. The coverage effects on the adsorption configrations and adsorption energies are addressed.