RESUMO
The influence on luminescence from conical bubble collapse (CBL) with varying Ar gas content while perturbing the liquid 1,2-Propanediol (PD) has been investigated. The temporal, spatial, and spectral features were analysed with regards to the dynamics of collapse and liquid degradation. Sulphuric acid and sodium chloride were added to disturb the liquid. The following three cases were studied: PD/Ar, (I), (PD + H(2)SO(4))/Ar, (II), and (PD + H(2)SO(4) + NaCl)/Ar, (III). The intensities of those cases decrease as III > II > I. Temporally, single and multiple light emissions were found to occur. The pulse shape exhibited a large variety of profiles with a main maximum and up to two local maxima around the main maximum. These local maxima resembled those generated by laser cavitation. Spatially, no radial symmetry was detected in the light emissions. Spectrally, the Swan, CH and CN lines were observed at low volumes of gas and driving pressure. The ·OH radical and OH-Ar bands, as well as the Na and K lines, consistently appeared superimposed on an underlying continuum that almost disappeared in (III). The Na line was observed with two satellite diffuse bands representing Na-Ar complexes in (I) and (II), whereas in (III), only the line of sodium could be seen. Weak and diffuse emission lines from the Ar atom in the near-IR region were observed in (I) and (II). The proposed mechanism of bright CBL was based on the energy transfer from electron-excited homolytic cleavage products to the chromophore molecules generated during the collapse-rebound time line (~8200 K and ~1 ms of collapse time from model), which had accumulated inside the liquid and remained on the walls of cavity during the repetition of the collapse. A general mechanism for the bright CBL is broached.
Assuntos
Argônio/química , Argônio/efeitos da radiação , Medições Luminescentes/métodos , Microbolhas , Sonicação/métodos , Gases/química , Gases/efeitos da radiação , Ondas de Choque de Alta Energia , Doses de Radiação , Análise Espectral , TemperaturaRESUMO
The LiNbO(3) congruent crystals doped with small Nd concentrations, <1 mol% Nd, and co-doped with Mg ions, 0-9 mol% Mg, were systematically investigated by means of micro-Raman spectroscopy in the Y and Z crystal directions. Results obtained from an undoped congruent crystal, an Nd-doped crystal, a Mg-doped crystal and Nd, Mg-co-doped crystals are compared. From the analyses of the results obtained in the Y direction, the Nd and Mg content dependence of the two lowest-Raman A(1)(TO(1)) and A(1)(TO(2)) modes, the half-width composition and the area ratio of the A(1)(TO(4)) and E(TO(8)) bands, we reached several conclusions about the incorporation mechanism of the Nd and Mg ions into the LiNbO(3) lattice. Likewise the Raman shift and half-width of the E(TO(1)) and E(TO(7)) modes were investigated in the Z direction. Results indicate that Mg and Nd ions are located in the Li site for low doping concentrations and for larger concentrations there is a replacement in both Li and Nb ion sites.
RESUMO
The principal component analysis (PCA) was applied to Raman spectra of polycrystalline BaTiO(3) under pressure from atmospheric pressure to approximately 6.72 GPa. For the system utilized, PCA was able to distinguish spectral features and to determine the phase transition pressure: tetragonal to cubic at approximately 2.0 GPa. The present study demonstrates the potentialities of the application of PCA to the investigation on phase transitions at high pressure by Raman spectroscopy.