Luminescence of SrX 2 microcrystals (X = Cl,I) activated with Eu2+ ions and dispersed in a NaI matrix

Luminescence spectroscopy has been used to determine the parameters of NaI-SrI₂-Eu, NaI-SrCl₂-Eu, and NaI-BaI₂-Eu compounds in the energy range of 3.7–18 eV at 10 and 295 K and investigate the phase formation in these crystalline systems. The NaI-SrI₂(1 mol %)-Eu(0.02 mol %) crystalline system has revealed formation of SrI₂ microcrystals activated with europium ions and dispersed in the NaI matrix. Formation of SrCl₂-Eu²⁺ microcrystals dispersed in a NaI matrix is observed for NaI-SrCl₂(1 mol %)-Eu(0.02 mol %) crystalline system. The mechanisms of aggregation of impurity ions and specific features of luminescence excitation for europium ions in dispersed microcrystals are discussed.     

Effect of spatial constraints on phase separation during polymerization in sequential semi-interpenetrating polymer networks

The viscoelastic properties of sequential semi-interpenetrating polymer networks prepared via the swelling of network polyurethane in different monomers (butyl methacrylate, styrene) followed by their polymerization in the polyurethane matrix have been studied by means of dynamic mechanical analysis. It is found that the relaxation behavior of the test systems and the degree of segregation of the components depends on M _c of the polyurethane matrix because of a change in the molecular mass of the polymer block. The compatibility of the components in sequential semi-interpenetrating polymer networks substantially increases when the network inner space in the polyurethane matrix decreases.     

Spontaneous radiation of molecules in open cavities

Within the framework of classical electrodynamics, a formula is derived for the spontaneous radiation rate of molecules and atoms in an arbitrary open cavity in the weak coupling approximation with allowance made for radiation absorption or amplification by the cavity material. The formula agrees well with microdroplet luminescence data. The effect of suppression of the spontaneous resonance radiation rate by the active laser medium is predicted.     

Investigation of vibrational relaxation of excimers

The excimer vibtational relaxation have been studied in the diffusional approximation, and stationary substantially non-equilibrium populations of high vibrational levels have been found. New formulae have been derived for quantum yield of UV lasing. Taking into account the vibrational relaxation the new effect of far-IR radiation amplification in the active media of excimer lasers is predicted.     

Peculiarities of KrF excimer vibrational relaxation in low-pressure Kr/F2 mixtures excited by a short pulse

The importance of excimer vibrational relaxation is manifested once again by the example of the low-pressure Kr/F₂ gain medium excited by a short pulse. The pressure is determined at which a sharp fall of the population efficiency of low KrF(B) vibrational levels should appear. Time peculiarities of the gain are investigated analytically for short-pulse excitation operation.     

Polypropylene/polyperoxide interaction in the melt phase

This paper deals with the effect of polyperoxide on the properties and characteristics of PP. Interaction of PP with polyperoxide was carried out by their mixing in melt phase applying co‐rotating twin screw machine. The analysis of melting/crystallisation processes was performed using DSC. Influence of polyperoxide concentration and mixing condition (temperature, residence time) on PP properties was investigated via determination of PP molecular weight. Mechanism of the PP degradation and decomposition of peroxide groups was judged by thermogravimetric analysis, FT‐IR‐, and NMR‐spectroscopy. It was observed that decomposition of peroxide groups brings about degradation of polypropylene. However, simultaneously some part of short, chains of PP are grafted onto macrochain of the polyperoxide decomposed.