Search

We have evaluated the surface plasmon dispersion relation in the presence of the inhomogeneous surface zone which has been proposed for liquid mercury. Assuming that photon-plasmon coupling occurs through the mechanism of frustrated total reflection, we find the dispersion relation to be sensitive to the existence of such a zone, providing retardation effects are taken into account. The results, it is believed, define nonradiative surface plasmon absorption as a useful technique for the study of conducting surfaces.

The absorption of light by surface plasmons has been studied using the method of attenuated total reflection. The reflectance from a quartz-Ag interface has been measured as a function of angle and surface structure for the wavelength region from 3600 to 6000 . It is shown that the reflectance minimum for a smooth Ag film is changed in both angular position and spectral half-width by roughening the Ag surface with CaF 2 underlayers. Dispersion curves are presented which show that the wave vector of a surface plasmon propagating on an irregular surface is greater than that of an equally energetic surface plasmon propagating on a planar surface.

We report the first experimental and theoretical investigation of the coupling of second-harmonic generation of light to surface plasmons in thin silver films. A model of second-harmonic generation due to polarization sources at the silver-air interface correctly predicts the observed harmonic enhancement of one and a half orders of magnitude because of excitation of the surface plasmon.

The observation of a broad ‘atomic plasmon’ resonance, recently predicted by Wendin is reported, together with a number of discrete features due to excitation of a single electron from the 4d subshell in Ba I. HartreeFock calculations indicate mixing between configurations built on 4d95p66s2, 4d95p65d 6s and 4d95p65d2of Ba II. Discrepancies between Wendin’s theory and experiment are attributed to this mixing. The spectrum near 16 Å arising by excitation of the 3d subshell has also been observed.

The inelastic-scattering probability of low-energy electrons due to the bulk- and surface-plasmon excitations is calculated using the infinite-square-barrier model. When the dispersion of the plasmons is neglected, the probability becomes the one derived by using the high-frequency step-density model. In order to consider the scattering by the lattices and the absorption effects for an incident electron, the distorted-wave method is used, which upon some manipulation gives essentially the same inelastic intensities as the ones given by Duke and Laramore. Some numerical calculations are performed for the Al(111) surface, and it is found that the absorption plays an important role in determining the intensity for the bulk plasmon relative to the one for the surface plasmon, and the cutoff wave numer at $k=0$ has some influence on the angular profile. The intensities obtained in this paper are qualitatively in agreement with the experimental results.

A hologram has been made using a surface plasmon resonance wave as the reference beam. The surface wave was stimulated on a 1200-line/mm aluminum reflection grating that was coated with a thin layer of high-resolution photographic emulsion. Experimental results are presented.

Experimental evidence is presented for the existence of both the volume and surface photoelectric effects in aluminum. Good agreement is obtained between the observed strengths of the surface effect and the predictions of the Mitchell-Makinson theories when the photoemission due to surface plasmon decay is divided into surface and volume photoeffect components.

The nonlocal surface plasmon dispersion relation in a quantizing magnetic field perpendicular to the surface is analysed, and the linear wave number shift of the principal surface plasmon mode is calculated in a way that incorporates Landau quantization effects for both the degenerate and nondegenerate cases. This mode is seen to be heavily damped when omega c>or= omega p in the electrostatic (nonretarded) regime.

The charge density fluctuation in a surface plasmon is calculated for a step-potential model of an Al surface. At low K the plasmon is largely localized to within an atomic radius of the surface, but at high K no localized mode is found. The dispersion relation is found for low K.

Anomalous polarization peaks in the first-order on-blaze diffraction spectra from concave reflecting gratings have been analysed in terms of a surface plasmon resonance in the grating surface for various metal and dielectric layers on the metal substrate. Non-radiative surface plasmon dispersion curves have been constructed from the experimental data and compared with classical dispersion curves based on the propagation of surface plasma waves. The cases considered were diffusion pump oil and aluminum oxide layers on an aluminum substrate and a multilayer of the type vacuum–dielectric–metal–dielectric–metal where the dielectric is aluminum oxide and the metal is aluminum. The wavelength region investigated was from the visible through the vacuum ultraviolet (7000 to 500 A). Shifts to longer wavelengths of the anomalous polarization peaks were found for both the double dielectric layer and the multilayer that were in good agreement with the appropriate theoretical non-radiative surface plasma wave modes. Anomale Polarisationsmaxima im Blaze-Beugungsspektrum erster Ordnung von konkaven reflektierenden Gittern wurden mit Oberflachenplasmonenresonanz in der Gitteroberflache fur verschiedene Metalle und dielektrische Schichten auf Metallsubstraten analysiert. Dispersionskurven nichtstrahlender Oberflachenplasmonen wurden aus den experimentellen Werten konstruiert und mit klassischen Dispersionskurven, die auf der Ausbreitung von Oberflachenplasmawellen basierten, verglichen. Die betrachteten Falle sind Diffusionspumpenol und Aluminiumoxydschichten auf Aluminiumsubstraten und eine Mehrfachschicht vom Typ Vakuum–Dielektrikum–Metall–Dielektrikum–Metall, wobei das Dielektrikum Aluminiumoxyd und das Metall Aluminium ist. Der untersuchte Wellenlangenbereich erstreckte sich vom sichtbaren bis zum Vakuum-UV-Bereich (7000 bis 500 A). Verschiebungen der anomalen Polarisationsmaxima zu langeren Wellenlangen, die in guter Ubereinstimmung mit geeigneten theoretischen, nichtstrahlenden Oberflachenplasmawellenmoden sind, wurden sowohl fur die dielektrische Doppelschicht als auch fur die Mehrfachschicht gefunden.

Landau damping results from the loss of energy of collective motion to the excitation of individual particles. Well known for plasmons, it can also occur for phonons and photons, as is shown herein. For a coupled longitudinal plasmon-optical-phonon wave, it can be significant both near the phonon resonance and near the plasmon resonance. It is generally insignificant for coupled transverse photon-optical-phonon waves. These results are important for infrared spectroscopy and Raman scattering involving plasmons and optical phonons.

The plasmon threshold experiment reported in the preceding letter is analysed and implications on surface and volume plasmon dispersion laws are drawn. It is concluded that there does not exist today any theoretical surface plasmon dispersion law able to describe the experimental result for short wavelengths. The volume plasmon threshold has a dependence on the electron density in accordance with the result from the Random Phase Approximation.

An electromagnetic analysis of a black-box type yields a general model-independent surface plasmon dispersion relation. This confirms and extends the validity of Harris and Griffin's formula 2 in terms of the charge density fluctuation and its dipole moment, but it shows furthermore that there is an extra term due to surface current fluctuations. In the RPA the effect of this term is zero, but a very crude estimate of the effect of diffuse surface scattering of the carriers indicates that it could account for a good fraction of the observed and otherwise calculated 3 order of magnitude of the surface plasmon lifetimes in metals.

Described are the resonance effects associated with surface plasmon excitation (the excitation of evanescent electro-magnetic surface waves) which occur when light is reflected from metal gratings and rough surfaces.

Anomalies found in the intensity of $p$-polarized light from concave diffraction gratings have been analyzed in terms of an interaction between the incoming photon and a surface-plasmon resonance in the grating surface. There is clear evidence for zone gaps in the dispersion curves which we have constructed for surface plasmons in Al and Au. The phenomena reported here may be regarded as manifestations of second- and possibly higher-order plasmon-grating interactions.

A method is described of directly coupling an optical beam to surface excitations. Using this technique the frequency and linewidth of surface plasmons in doped germanium and in gold and surface phonons in calcium molybdate are determined. The method also allows the dispersion curve to be measured.

A theory of the intensity and shape of plasmon satellite bands in the soft X-ray emission spectra of aluminium, magnesium and sodium is proposed. Based on the Bohm and Pines semi-quantitative treatment of the electron gas, this theory is able to account very satisfactorily for the experimental data and provides a physical interpretation of the phenomenon. Because the electron undergoing the transition and the localized vacancy have opposite charges, their plasmon eigenfields partially cancel one another when the X-ray transition occurs. This interference effect is not total because of the slight difference between the two plasmon field frequencies which arises from the relative motion of the vacancy and electron. This explains the occurrence and the weak intensity of the plasmon emission. The dispersion of the plasmon frequency provides an explanation of the profile of the plasmon satellites. Similar effects must occur when the electron-positron annihilation in a metal is accompanied by the emission of a real plasmon.

Measurements of the resonant excitation of surface plasmons at both the air and substrate surfaces of evaporated Ag films indicate that the real part of eAg is a larger negative number at the substrate interface. This difference can be explained with a Maxwell‐Garnett type theory which assumes that the film density near the air surface is several percent below that near the substrate interface.

The agreement between a recently propounded theory of metallic surface energies and experiment is a consequence of the arbitrary choice of the same plasmon cut-off wave-vector, k c , for both bulk and surface plasmons. With a more reasonable choice of k c 's, the ‘plasmon theory’ predicts negative surface energies.

The local surface plasmon dispersion relation for a slab of plasma in a magnetic field (perpendicular to the slab faces) is analyzed. Magnetic field modifications of both antisymmetric and symmetric slab surface plasmon modes are determined in the local limit.

Gold nanoshells are new constructional units consisting of dielectric core encapsulated by gold nano- layer that exhibits a plasmon-derived optical resonance typically shifted to near-infrared (NIR) wavelengths (800∼1200 nm). The fabrication of gold nanoshell was optimized based on the relative contributions of the aging of gold colloids, concentration of reducible gold salts, and dosages of formaldehyde reducing agents. One-week-aged gold colloids produced a relatively monodisperse deposition of gold seeds onto silica nano- particles, whereas one-day-aged gold colloids produced a heterogeneous deposition of gold seeds on the silica nanoparticle surfaces. At the optimal dosages of reducing agents, the thickness of the gold layer increased with the increment of the concentrations of the reducible gold salts, consequently leading to the smoother morphol- ogies and stronger plasmon resonances of the gold nanoshells. The excessive addition of gold salts and/or re- ducing agents, however, resulted in a significant reduction of the plasmon resonance because of the increased aggregation between the gold nanoparticles.

The dispersion of surface plasmons at an air-metal interface has been studied experimentally using the method of attenuated total reflection. In the vicinity of the surface plasmon energy the dispersion curve was found to bend back toward the light line instead of increasing asymptotically to the surface plasmon energy at infinite momentum. We conclude that surface plasmon interactions must be characterized by a complete response-function surface rather than by a single dispersion curve.

The effect of a dc magnetic field of arbitrary magnitude and orienation on surface plasmons in a metal or degenerate semiconductor is studied in the "nonretarded" limit.

A microscopic theory of barrier heights at metal-semiconductor interfaces is proposed. The theory explains the resonance in barrier adjustability as a function of semiconductor ionicity described by Mead et al., in terms of the interfacial-surface plasmon energy and the covalent-bond energy of the semiconductor.

Energy spectra of electrons reflected at a very smooth surface of liquid indium show both energy losses due to the excitation of surface plasmons (8.4 eV) and multiple peaks which correspond to a gain of one surface plasmon.

The plasmon spectrum is investigated in the quantum strong field limit, (ℏωc > ζ ∼ EF). We find another set of plasmon resonances in addition to those already discussed in the literature. This new set of resonances is only very mildly damped under appropriate conditions of low wavenumber. Under such low wavenumber conditions, the new resonances are of comparable importance (in terms of excitation amplitude) with other resonances previously reported. The result is that there are two plasmon resonances which lie near each multiple of the cyclotron frequency, except for propagation nearly perpendicular to the magnetic field.

Granular films of alkali and coinage meta ls are the most popular objects for expl oring plasmonic effects. They are easy to obtain via physical vapor deposition and to study via optical means. In this contribution we show several ways not only to record but also to modify the granular meta l films using thermal and nonthermal optical effects. Keywords: metal nanoparticles, plasmon resonance, dephasing time, surface diffusion, surface morphology, laser assisted growth INTRODUCTION Granular metal films have found a numb er of applications. They are employed in surface e nhanced Raman scattering, fast and sensitive photodetection, high performance photovoltaic s, as well as in many other existing and emerging areas. Bright optical properties of granular metal films form the basis of these applications. On the other hand, optical means may be used to shape and to study granular metal films. Granular metal films obtained via physical vapor deposition comprise nanoparticles with wide size and shape distributions. This property is detrimental in some applications. Selective reshaping of silver nanoparticles under the pulsed ruby laser illumination is shown to significantly change the shape distribution. On the other hand this process may be used to reveal the homogeneous width of the plasmon resonance in the particles of definite shape otherwise hidden under the inhomogeneous broadening of the whole ensemble.

Inelastic scattering of charges by metal surface plasmons is described in terms of coherent excitation of the harmonic plasmon fields. Several applications are discussed. Coherent plasmon states provide a clear insight into the quantum mechanical nature of the classical image charge.

The reflectance of silver decreases in the energy range of surface plasmons because of coupling between light and surface waves via surface roughness.

The surface structure autocorrelation function of evaporated thick silver layers contains quasiperiodic terms due to preferred sizes and distances of surface irregularities. This determines the angular dependence of the electron induced surface plasmon radiation.

Using the R.P.A., we relate the term in the surface plasmon energy which is linear in k| to the charge dipole associated with the density fluctuation.

The plasmon contribution to the optical absorption in sodium has been calculated numerically by using up to k 6 term in the plasmon frequency and a proper plasmon renormalization factor. The resulting peak is about one third of that obtained in previous calculations.

We have calculated the probability of surface plasmon generation at a rough surface of a thick dielectric slab by means of first-order perturbation theory. Comparison is made with the results of Crowell and Ritchie, who treated the special case of reflectance of free-electron-like metal, and employed a different form of perturbation theory.

It is shown that (Al-MgF(2))-interference filters of better performance than have been predicted and obtained previously are possible in the uv below 2500 A. Experimental results are given for conventional filters of first and higher order and for new filter designs that use multilayer structures for the two mirrors of the filter. All discrepancies between theoretical and experimental results are explained by a coupling of light into the surface plasmon of aluminum via a surface roughness of the MgF(2) films.

In the RPA it is shown that the classical image charge is induced entirely by the surface plasmon and that the volume plasmon contributes nothing when the static test charge is outside the medium.