On the effect of microscopic roughness of the metal surface on the surface plasmon dispersion relation and photoemission

The effect of microscopic surface roughness on the opical characteristics of metal is considered. The field near the rough surface has been calculated on the basis of integral equations containing only smoothly varying field components. It appears that the influence of surface plasmons can cause, as a result of drastic enhancement of the field at the surface, an increase by several orders in such observed surface effects as photoemission and Raman scattering by adsorbed molecules. The results of calculation are compared with the experimental data obtained from the study of photoemission from silver with rough surface. Expressions have been derived for the dispersion relation for surface plasmons on a rough surface.     

Coupling of spontaneous emission from GaN-AlN quantum dots into silver surface plasmons

We have demonstrated the decay of spontaneous emission (SE) from AlN-GaN quantum dots (QDs) into silver surface plasmon (SP) modes in the ultraviolet at approximately 375-380 nm. Using time-resolved photoluminescence (PL), we show that the electron-hole recombination rate in AlN-GaN QDs is enhanced when SE is resonantly coupled to a metal SP mode, corresponding to the dip in the continuous-wave PL spectrum. Exciton recombination by means of silver SP modes is as much as 3-7 times faster than in normal QD SE and depends strongly on emission wavelength and thickness of the silver.     

Two resonances effect for light transmission assisted with surface plasmon through perforated metal film

When light is incident on a nonplanar metal surface, an oscillating dipole is excited at the entrance openings. We show that the enhanced transmission assisted with surface plasmon (SP) through a perforated metal film results from two different SP resonances effects: (i) zero-order Fabry-Perot resonance effect where each air hole can be considered as a section of metallic waveguide, forming a low-quality-factor resonator, and many dipoles are arranged inside the nanoholes region; and (ii) structure-factor-induced charges self-tunnelling effect due to the well-recognized surface structure periodicity, where the positive or negative charges can respectively tunnel into the right surface through the metal walls. Furthermore, when light transmits through the double-layer perforated metal films, the different transport behaviors are also clearly shown, which convinces the existence of dual SP resonances effect.     

Effective impedance spectra for predicting rough sea effects on atmospheric impulsive sounds

Two methods of calculating the effective impedance spectra of acoustically hard, randomly rough, two-dimensional surfaces valid for acoustic wavelengths large compared with the roughness scales have been explored. The first method uses the complex excess attenuation spectrum due to a point source above a rough boundary predicted by a boundary element method (BEM) and solves for effective impedance roots identified by a winding number integral method. The second method is based on an analytical theory in which the contributions from random distributions of surface scatterers are summed to obtain the total scattered field. Effective impedance spectra deduced from measurements of the complex excess attenuation above 2D randomly rough surfaces formed by semicylinders and wedges have been compared to predictions from the two approaches. Although the analytical theory gives relatively poor predictions, BEM-deduced effective impedance spectra agree tolerably well with measured data. Simple polynomials have been found to fit BEM-deduced spectra for surfaces formed by intersecting parabolas corresponding to average roughness heights between 0.25 and 7.5 m and for five incidence angles for each average height. Predicted effects of sea-surface roughness on sonic boom profiles and rise time are comparable to those due to turbulence and molecular relaxation effects.     

Two surface plasmon resonances effects for light through the perforated metal film

Light transmission through perforated metal film has been reported and some investigations have been made into the physical origin of this phenomenon. We show that the transmission assisted with surface plasmon (SP) through a perforated metal film results from two different SP resonances effects: surface plasmon resonance due to the periodicity at the left air/metal and right metal/air interfaces and localized cavities resonance inside rectangular holes. The fields intensity is localized separately on the left and right metal-air surfaces for structure-factor-induced surface plasmon mode. And for localized cavities resonance mode, standing electromagnetic fields can also be entirely localized inside the nanohole region. The aspect ratio of the rectangular holes can affect the transmission.     

The main results of cloud and rain remote sensing by multichannel microwave radiometry

The basic results have been considered for multiwave remote sounding of the troposphere with clouds and rain from ground-based station in the zenith direction. The radio wave scattering by rain drops as well as variation of vapour content in the atmosphere during measurements are taken into account when processing of the experimental data. A separation of the complete attenuation in clouds with rain has been made over three components: due to vapour, cloud and rain. A relation is considered of millimeter and centimeter wave attenuation in clouds with rain between each other and with the rain intensity. A behaviour of the relation of attenuation structural functions is explained. The Diagnostic problems of millimeter wave attenuation are considered.     

Effects of adsorbate-induced states on the metastable He atom scattering from water- and benzene-adsorbed Cu(1 0 0)

The intensity of metastable helium (He*) atoms which survive during the scattering from water- and benzene-adsorbed Cu(1 0 0) surfaces was measured. The survival probability (SP) of He* was found to be sensitive to the electronic states at around the Fermi level, which is derived from the adsorbate/metal hybridization and extend toward the vacuum. The SP is likely to depend largely on the kinetic energy of the He* atoms. The kinetic energy dependence can be understood on the basis of the He* decay mechanism. Metastable-atom deexcitation spectroscopy (MDS) and surface electronic structure calculation have been used for discussing the results for the He* SP.     

Dispersion and damping of a surface plasmon polariton on a one-dimensional randomly rough metal surface

Abstract

By the use of the reduced Rayleigh equation for the amplitude of a surface plasmon polariton on a one-dimensional randomly rough metal surface that is in contact with vacuum, we calculate the dispersion and damping of the surface electromagnetic wave to the lowest nonzero order in the rms height of the surface. It is found that the frequency of the surface plasmon polariton is depressed by the surface roughness. The attenuation of the surface plasmon polariton in the long wavelength limit is due primarily to its scattering into other surface plasmon polaritons, while in the short wavelength limit it is due primarily to its roughness-induced scattering into volume electromagnetic waves in the vacuum. The energy mean free path of the surface plasmon polariton is shorter on a randomly rough metal surface than it is on a lossy planar metal surface, and the surface plasmon polariton is more tightly bound to a rough surface than to a planar one.     

Surface-enhanced emission from single semiconductor nanocrystals

The fluorescence behavior of single CdSe(ZnS) core-shell nanocrystal (NC) quantum dots is dramatically affected by electromagnetic interactions with a rough metal film. Observed changes include a fivefold increase in the observed fluorescence intensity of single NCs, a striking reduction in their fluorescence blinking behavior, complete conversion of the emission polarization to linear, and single NC exciton lifetimes that are >10(3) times faster. The enhanced excited state decay process for NCs coupled to rough metal substrates effectively competes with the Auger relaxation process, allowing us to observe both charged and neutral exciton emission from these NC quantum dots.     

Plasmon surface polariton luminescence from periodic metal gratings

When a gold grating is illuminated at an appropriate energy, polarization, and angle to excite a plasmon surface polariton (SP) all lower energy radiative SP states emit light. This enables the dispersion of SP states to be mapped by luminescence providing an alternative to reflectivity measurements. A similar effect has been observed for bare silver gratings, and silver gratings coated with several layers of cadmium arachidate by Langmuir-Blodgett technique. Two additional effects have been observed for Au gratings. First, one can obtain emission from radiative SP states by exciting the interband transition directly with photons of energy greater than approximately 2.4 eV. At these energies, SP states do not exist because the metal dielectric function has a large imaginary part. This is significant because it suggests that the degradation pathway involves electron-hole pair states as intermediates. Second, some gold gratings show $\text{surface enhanced Raman}$ of molecular species superimposed on the SP luminescence emission.     

Plasmonic metasurfaces for waveguiding and field enhancement

The explosive progress in nanoscience has led to uncovering and exploring numerous physical phenomena occurring at nanoscale, especially when metal nanostructures are involved so that optical fields and electronic oscillations can be resonantly coupled. The latter is the subject of (nano) plasmonics with implications extending from subwavelength waveguiding to localized field enhancements. In this review paper, we consider making use of various phenomena related to multiple scattering of surface plasmons (SPs) at periodically and randomly (nano) structured metal surfaces. After reviewing the SP waveguiding along channels in nanostructured areas exhibiting band‐gap and localization effects, SP‐driven field enhancement in random structures and plasmonic fractal drums is discussed in detail. SP manipulation and waveguiding using periodic nanostructures on the long‐wavelength side of the band gap is also considered.     

Dispersion and attenuation of surface shear acoustic waves with horizontal polarization on the free statistically rough surface of the hexagonal crystal

Expressions for dispersion of the phase velocity and inverse damping depth of surface acoustic waves with shear horizontal polarization are derived in an analytical form within perturbation theory using the modified mean-field method for the Z-cut hexagonal crystal with a free statically rough surface. Both two-and one-dimensionally rough surfaces are considered. The one-dimensionally rough surface is considered as a special case of the two-dimensionally rough surface. It is shown that shear surface waves with horizontal polarization cannot exist on the flat surface of the Z-cut hexagonal crystal. The derived expressions are studied analytically and numerically in the entire frequency range accessible in perturbation theory. The long-wavelength limit (most interesting from the experimental point of view) is considered, where the wavelength is much longer than the roughness correlation radius. The conditions for the existence of SH-polarized waves are determined for both roughness types. It is shown that dispersion and attenuation of SH polarized waves are qualitatively similar in character to those we considered previously for an isotropic medium.     

Identification of molecules through the fluorescence enhancement by a metal tip

A fluorescence enhancement phenomenon, which is realized as a result of a sharp increase in the radiative decay rate of a quantum dipole emitter (QDE) is investigated theoretically in the vicinity of a conical metal tip. The QDE relaxation process is considered as a self-stimulated transition from an excited state into the ground state due to the feedback field formation from the tip. The dynamics of the system shows a stepped relaxation behavior that differs significantly from the conventional exponential decay. This effect can be observed in a small region of the resonance frequency, which is defined by an angle of conical tip. The increase of fluorescence when approaching of molecule to the metal tip on the surface enables one to determine its location.     

Leak noise propagation and attenuation in submerged plastic water pipes

Detection of water leaks in buried distribution pipes using acoustic methods is common practice in many countries. Correlation techniques are widely used in leak detection, and these have been extremely effective when attempting to locate leaks in metal pipes. However, a number of difficulties have been highlighted when trying to determine the position of leaks in plastic pipes. Of particular interest here is what happens to the leak noise when the pipe passes through an expanse of water, such as across a river or lake.In this paper, the low-frequency acoustic propagation and attenuation characteristics of a submerged plastic water pipe are investigated experimentally in the laboratory, supported by predictions from a theoretical model. It is found that, whilst the signal attenuation for a submerged pipe is increased relative to that for a similar in-vacuo pipe, energy does not, in fact, radiate into the water; furthermore, the attenuation is small compared with that for a pipe buried in soil.     

Propagation effects of a fractal rough ocean surface on the vertical electric field generated by lightning return strokes

Based on an improved two-dimension (2D) fractal model of rough ocean surface, the propagation effects of the rough ocean surface on the vertical electric fields generated by lightning return strokes are analyzed. The results show that the rough ocean surface has much effect on the electric field derivatives, but has no or little effect on the field peaks. The frequency above 10 MHz is attenuated significantly by the rough ocean surface, and the rapid attenuation of frequency above 10 MHz in the experimentally obtained spectrum may be taken into account the errors introduced by the roughness of the ocean surface.     

Decay of high-frequency acoustic excitations in chain-type lattices and weak localization

The attenuation of high-frequency sound in disordered quasi-one-dimensional semiconducting and dielectric crystals, which is associated with three-phonon decay and elastic scattering by structure defects is considered theoretically. It is shown that specific interference processes occurring in the regime of weak localization of acoustic vibrational excitations considerably affect the propagation of sound. This mechanism of sound attenuation can be observed experimentally from the anomalies in the frequency dependence of the reciprocal attenuation length of sound.     

Absorption of surface plasmons in a metal-cladding layer-air structure in the terahertz frequency range

The effect of a thin dielectric cladding layer of a metal on the absorption of surface plasmons (SPs) in the terahertz frequency range is studied experimentally and numerically. It is found that, as the radiation wavelength increases, the attenuation of SPs caused by the cladding layer can increase by a factor of ～10⁴ as compared to the absorption of SPs propagating along the unperturbed metal-air interface. Data obtained in experiments with germanium-cladded aluminum specimens using radiation from a terahertz free-electron laser (v = 90 cm^?1) confirm that application of a dielectric cladding on the metal surface causes the SP absorption to increase.     

The absorption of rayleigh's sound waves in metals in a parallel magnetic field

The electron absorption coefficient has been calculated for the Rayleigh waves in a metal, with the magnetic field parallel to the boundary. Reflection of electrons from the metal surface is assumed to diffuse. For high magnetic fields the shape and width of the absorption lines have been investigated as well as maximum values of the attenuation. For low fields oscillations of the geometric and cyclotron resonance type are predicted.     

Rare decay modes of fission fragments

The experimental data on rare modes of radioactive decay of fission fragments is reviewed. These decay modes are due to a large excess of neutrons and a high energy of β decay fragments. They appear in delayed emission of various particles after the β decay (several neutrons, α particles, or heavy clusters) and excitation of unusual states (giant multipole resonances and shape isomers). The β decay and internal conversion of γ radiation into bound states of the atomic electron shell and their influence on the probability of secondary particle emission are considered. The possibility is discussed of observing decays that have not yet been experimentally detected, but theoretically predicted, as well as information on the nuclear structure obtained by studying such decay modes.     

Fractional precursors in random media

When a broadband pulse penetrates into a dissipative and dispersive medium, phase dispersion and frequency-dependent attenuation alter the pulse in a way that results in the appearance of a precursor field with an algebraic decay. We derive here the existence of precursors in non-dispersive, non-dissipative, but randomly heterogeneous and multiscale media. The shape of the precursor and its fractional power law decay with propagation distance depend on the random medium class. Three principal scattering precursor classes can be identified: (i) in exponentially decorrelating random media, and more generally in mixing random media, the precursor has a Gaussian shape and a peak amplitude that decays as the square root of the inverse of the propagation distance. (ii) In short-range correlation media, with rough multiscale medium fluctuations, the precursor has a skewed shape with a tail that exhibits an anomalous power law decay in time and a peak amplitude that exhibits an anomalous power law decay with propagation distance, both of which depend on the Hurst exponent that characterizes the roughness of the medium. (iii) In long-range correlation media with long-range memory, the situation mimics that of class (ii), but with modified power laws.