[en] The study of multicharged plasma production from aluminium target in dependence on frequency of pulsed-periodical laser was made and charge and mass spectra of ions were measured. The processes causing the generation of highly ionized plasma with laser frequency growth are discussed. (A.A.D.)

No abstract available

No abstract available

[en] A wide variety of thin film coatings, deposited by different techniques and with potential applications in various important areas, have been characterised by the Phase Modulated Spectroscopic Ellipsometer, installed recently in the Spectroscopy Division, B.A.R.C. The Phase Modulated technique provides a faster and more accurate data acquisition process than the conventional ellipsometry. The measured Ellipsometry spectra are fitted with theoretical spectra generated assuming an appropriate model regarding the sample. The fittings have been done objectively by minimising the squared difference (χ²) between the measured and calculated values of the ellipsometric parameters and thus accurate information have been derived regarding the thickness and optical constants (viz, the refractive index and extinction coefficient) of the different layers, the surface roughness and the inhomogeneities present in the layers. Measurements have been done on (i) ion-implanted Si-wafers to investigate the formation of SiC layers, (ii) phenyl- silane coating on glass to investigate the surface modifications achieved for better adsorption of rhodamine dye on glass, (iii) GaN films on quartz to investigate the formation of high quality GaN layers by sputtering of GaAs targets, (iv) Diamond-like-coating (DLC) samples prepared by Chemical Vapour Deposition (CVD) to investigate the optical properties which would ultimately lead to an accurate estimation of the ratio of sp³ and sp² bonded carbon atoms in the films and (v) SS 304 under different surface treatments to investigate the growth of different passive films. (author)

[en] Plasma oscillations (plasmons) in solids are collective electron charge-density oscillations. They are observed, e.g., as peaks in the electromagnetic absorption spectra of thin metal films, where several types of plasmon mode occur (bulk, surface, standing, two-dimensional). Metallic plasmons typically have frequencies in the ultraviolet region, but in the epitaxial GaAlAs system, the plasmons lie in the far infrared because of the small electron effective mass and high dielectric constant of the underlying semiconductor. Plasmons are therefore of interest for possible far-IR-active devices. They may also be a limiting factor in the design of ultrasmall (nanosized) transistors and other electronic components. An understanding of the mutual plasmons of separated nanostructures is a key to prediction of van der Waals or dispersion forces, with applications ranging into chemistry and biology. In positively charged metal clusters or metal films one can prove a harmonic potential theorem. This states that, despite the Coulomb interaction between the electrons, there is a mode in which the entire electron gas, including its highly inhomogeneous edge regions, moves rigidly at the bare harmonic-well frequency. This motion has proved to be a crucial test case for approximate theories of time-dependent many body phenomena. In particular, the author has shown that this test is failed both by the usual approximations for the ∇n pressure term in hydrodynamics, and by the most sophisticated expressions for the exchange-correlation kernel f_xc in time-dependent density functional theory. To rectify these failures the author has proposed modified theories

[en] We calculate the ac dielectric function of a model Drude metal-insulator composite, using a three-dimensional (d=3) transfer-matrix algorithm. The real part of the effective conductivity, Reg_e(ω), reveals (i) a Drude peak that appears only above the percolation threshold p_c; and (ii) a broad spectrum of surface-plasmon resonances whose lower edge approaches zero frequency at p_c. Sufficiently near p_c, the dielectric function is consistent with an expected scaling form previously verified in d=2. The surface-plasmon spectrum resembles effective-medium predictions except for a weak but persistent peak near 0.4ω/ω_p

[en] Anisotropic intrasubband magnetoplasmons of an electron gas in a wide parabolic quantum well are obtained by using a method within the framework of the random-phase approximation. The symmetries and shapes of the various perturbed Hartree potentials along the confining direction at B=0 are found analytically. Anisotropy of the intrasubband modes in the presence of a longitudinal magnetic field perpendicular to the confinement direction is revealed and explained. We also make a striking prediction that a strong longitudinal magnetic field can give rise to an additional one-dimensional-like undamped intrasubband magnetoplasmon mode which is well within the experimentally accessible range

[en] The purpose of this study is to develop calibration procedures by simulation code on the computer system instead of phantoms. Total-body potassium, mainly distributed in muscle mass, has been estimated by the Whole-body counter of the University of Tokyo. The subjects were counted with a plastic scintillation detector system for 10 minutes. It has high sensitivity, but its energy resolution is inevitably low. We used human-shaped water- and potassium-phantoms of five different sizes for calibration. There are considerable differences between physique of the subjects and shape and dimensions of phantoms. Physique varies from individual to individual and from time to time even in one individual, particularly in growth. So, we have been developing calibration procedures by the simulation. The EGS-4 simulation code was used. Countings given by the actual whole-body countings of potassium phantoms were used to evaluate the validity of the simulation code. Homogeneous potassium solution was assumed to be in the phantoms, and efficiency rates and energy spectra were assessed. Geometrical efficiency well agreed with actually observed one, which implies that the simulation procedures are able to provide reliable results. (author)

[en] We present an application of the current-density functional formalism to a nonuniform many-fermion system in a strong magnetic field. To this end, we construct a current-dependent local ground-state energy functional and derive self-consistent equations for the current density associated with a given density profile. We apply the formalism to the calculation of the surface properties of an electron-hole droplet and we find that the surface tension of the droplet is a rapidly increasing function of the magnetic field

[en] This dissertation consists of two parts covering two different topics. In the first part, Manson and Ritchie's self-energy formalism is applied to investigate the image potential for a charged particle near a solid surface. A generalization of this formalism to include high-order corrections is given. Numerical evaluation of the image potential is carried out using the complete and orthogonal basis set of Coulombic wave functions. Calculation of high-order corrections to the binding energy of electrons in image states is described. In the second part, a nonlinear mechanism of photon absorption by surface-plasmon excitation through intraband excitations facilitated by electron-ion interactions is investigated. Results indicate that this mechanism may make small corrections to the absorptance of photons at an Al metal surface. Further theoretical and experimental work in this area is indicated