A technique of the low-coherence reflectometry was applied to characterize the structure of foamed polylactide matrices. This technique is based on the analysis of the decaying output of a low-coherence scanning interferometer with a diffusively backscattering probed sample in the object arm. Estimations of the decay rate for the interferometer output allowed us to characterize the influence of the foaming parameters on the mean transport free path of light propagation in the examined foamed matrices. It was established that foaming in the vicinity of the critical point of the plasticizing and foaming agent (carbon dioxide) leads to a smaller average size of pores in the synthesized matrices compared to the foaming parameters far from the critical point.
Dielectric function of wide-zone semiconductor nanoparticles (titanium dioxide) was studied under the condition of laser pumping at various wavelengths. A closed-aperture z-scan method with simultaneous measurements of the right-anglescattered intensity was used to retrieve the real and imaginary parts of dielectric function in the dependence on the pump intensity. It was found that the efficiency of dielectric function modulation by pumping light strongly depends on detuning of the wavelength of pumping light with respect to the fundamental absorption band of nanoparticles. The ColeCole diagrammatic technique was applied for interpretation of the pump-induced changes of the dielectric function in the optical range. Applicability of the Kramers-Kronig relations for description of the observed behavior of the dielectric function is discussed.
Empirical data on the diffuse and collimated transmittance of aged liquid foams are discussed in terms of influence of mutual correlations in the scatter positions. This influence can be described introducing the static structure factor of a scattering system and occurs remarkable in the case of wet foams with gas bubbles as the basic scattering units. On the contrary, mutual correlations of basic scattering units (Plateau-Gibbs channels and vertices) in dry foams are negligible due to low values of their volume fraction. This causes dramatic changes of the scattering anisotropy of foam layers in the vicinity of the wet-to-dry transition. Some analogies can be drawn between this effect and a previously reported "optical inversion" of densely packed random media.
Results of the experimental study of changes in the bubble size statistics during aging of wet foams are discussed. It is proposed that the evolution of the bubble radii distributions can be described in terms of the one dimensional Fokker- Planck equation. The empirical distributions of the bubble radii exhibit a self-similarity of their shapes and can be transformed to a time-independent form using the radius renormalization. Analysis of obtained data allows us to suggest that the drift term of the Fokker-Planck equation dominates in comparison with the diffusion term in the case of aging of isolated quasi-stable wet foams.
Details of the dislocation interaction with exitons in deformated crystals are considered. This phenomenon is studied by calculating method of energy dissipation caused by the quantum transitions of the excitons induced by external disturbance. The dependence of deceleration force via dislocation velocity in some ranges was obtained.
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