Optical phase-space distributions for low-coherence light

Using a novel heterodyne technique, we measure optical phase-space distributions in momentum and position for low-coherence light. Quantitative information is obtained simultaneously about the longitudinal and the transverse coherence properties as well as the wave-front curvature of the light field. This method can be used to monitor these optical parameters directly for signal fields scattered from samples of interest, for tomographic imaging.     

Absorption spectra and light penetration depth of normal and pathologically altered human skin

A three-layered skin model (stratum corneum, epidermis, and dermis) and engineering formulas for radiative transfer theory are used to study absorption spectra and light penetration depths of normal and pathologically altered skin. The formulas include small-angle and asymptotic approximations and a layer-addition method. These characteristics are calculated for wavelengths used for low-intensity laser therapy. We examined several pathologies such as vitiligo, edema, erythematosus lupus, and subcutaneous wound, for which the bulk concentrations of melanin and blood vessels or tissue structure (for subcutaneous wound) change compared with normal skin. The penetration depth spectrum is very similar to the inverted blood absorption spectrum. In other words, the depth is minimal at blood absorption maxima. The calculated absorption spectra enable the power and irradiation wavelength providing the required light effect to be selected. Relationships between the penetration depth and the diffuse reflectance coefficient of skin (unambiguously expressed through the absorption coefficient) are analyzed at different wavelengths. This makes it possible to find relationships between the light fields inside and outside the tissue. __________ Translated from Zhurnal Prikladnoi Spektroskopii Vol. 74, No. 3, pp. 387–394, May–June, 2007.     

Depth distributions of Au recoil atoms in silicon

The depth distributions of Au recoil atoms in Si have been investigated for Ar, Kr, and Xe ions implantation in 25–30 nm of an Au-Si system. The profiles were measured by means of RBS and radioactive techniques. The experimental results were compared with theoretical Gras-Marti analytical expressions and Monte-Carlo simulated depth distributions.     

Enhanced raman scattering spectra for gaussian light beams

We show that effect of light-induced focusing of the low-frequency Raman scattering components and defocusing of the high-frequency components in the field of a gaussian exciting beam lead to a slight shift of the enhanced Raman line relative to the center of the spontaneous Raman line on the low-frequency side. We propose and provide a rationale for an efficient algorithm for calculating the average power for enhanced Raman scattering, based on numerical solution of the wave equation for the field of the Stokes beam developing from spontaneous Raman scattering. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 2, pp. 230–236, March–April, 2007.     

Time-resolved phase-space distributions for light backscattered from a disordered medium

We demonstrate time-resolved measurement of optical phase-space distributions as a new probe for investigating the propagation of light in disordered media. Phase-space techniques measure the joint transverse position and momentum distribution of the scattered light, and are sensitive to the spatially varying phase and amplitude of the field. Using this method we investigate light backscattered from a random medium. The measurements indicate that the weakly localized component is a phase conjugate of the incident light field. A new model of backscatter, based on Wigner phase-space distributions, elucidates the spatial and angular behavior of the localized and unlocalized components.     

Polarization distributions and degree of polarization for quantum Gaussian light fields

We examine polarization properties of electromagnetic field states with Gaussian complex-amplitude distributions, such as quadrature coherent and squeezed states, thermal chaotic states, and two-mode squeezed vacuum states. We compute their polarization distribution and we apply to them diverse measures of degree of polarization and polarization fluctuations. This allows us to investigate the main properties of the degrees of polarization introduced so far.     

Bounds on multiplicity distributions from one-particle inclusive spectra

Using energy conservation sum rules, we derive bounds on multiplicity distributions in terms of one-particle inclusive spectra.     

Mass spectra of meson molecular states for heavy and light sectors

We obtain mass spectra of the light and heavy meson-antimeson(molecular states) sectors by using a nonrelativistic potential model with Coulomb and one pion exchange potential terms for meson-meson interaction.The digamma decay widths are also obtained for the light sector.We compare our results with available experimental and theoretical data.     

Depth sensitivity of X-e− coincidence Mössbauer scattering spectra

The performance of the X-ray — e⁻ coincidence technique for recording depth selective⁵⁷Fe CEMS spectra was investigated. The technique proved useful for selection of K-shell conversion electrons (7.3 keV) from a beam of back scattered electrons. This makes it possible to observe the depth sensitivity of CEMS spectra recorded with an He/CH₄ flow proportional counter.     

Modified action for light quarks in the instanton vacuum

The procedure of averaging in an instanton medium in quarks with any number of flavors is discussed. It is shown that the effect of the instanton medium is equivalent to an interaction of light quarks with dynamically generated mass (four-quark interaction N _f = 2) and massless bosonic spinor fields (ghosts). The fact that the instanton liquid is dilute makes it possible to use perturbation theory. The article is published in the original.     

Reflections of light by the gradient of refractive-index distributions

We report the results of observation of weakly luminous rays produced by the gaussian beam incidence on the surface of inhomogeneous dielectric materials. These rays are experimentally distinguished from the ordinary geometrical optics rays that are reflected at the air-dielectric interface. The results are consistent with the theoretical prediction that the luminous phenomenon is caused by the reflection of the incident ray at every point in the inhomogeneous medium.     

Photoelectron spectra induced by broad-band chaotic light

We consider a model for laser-induced autoionisation in which the laser light is treated as a chaotic white noise. We solve a set of coupled stochastic integro-differential equations, which are based on the Fano model for autoionisation. For the case of symmetric Fano profile we determine the exact photoelectron spectrum and compare it with the results of previous models including different (diagonal and off-diagonal) relaxation mechanisms, and also spontaneous emission. It is interesting to note that equations of our model are of great similarity to those in the model with radiation damping.     

Depth distributions of implanted atoms under the influence of surface erosion and diffusion

Shallow range distributions are altered significantly by diffusion and surface erosion. It will be shown here that the simultaneous processes of implantation, diffusion, and surface erosion can be described by a second order differential equation which is mathematically tractable and yields general results in terms of analytical functions. The resulting depth distributions depend on one parameter only which is a combination of the mean particle range, the diffusion coefficient, and the velocity of surface erosion (e.g. sputtering). The theory is applied to practical cases, e.g. implantation of plasma particles in the wall of fusion reactors, or solar wind ions in the surface of meteorite materials.