Espectroscopia de luminescencia resolvida no tempo : implementação da tecnica e aplicações

AUTOR(ES)
DATA DE PUBLICAÇÃO

1992

RESUMO

Initially, the optimization of the SR250 Boxcar integrator and averager s parameters for excited-state lifetime measurements was performed. A quantitative theoretical model which takes into account the linear RC time constant distortions on the excited-state lifetime (t) decay waveforms was proposed. The computer simulations using a mathematical expression, derived from the model, is in good agreement with the experimental decay curves. The results showed that the expression can be applied to the optimization of instrumental parameters, as well as in least-squares data reduction methods for luminescence kinetics measurements. After this, the interfacing of the equipment to a microcomputer was performed, allowing the implementation of the technique Time-Resolved Luminescence Spectroscopy. The interfaced instrumentation was used for spectroscopic and kinetic investigation of the luminescence of solid uranyl compounds. The first study, on powder uranyl nitrate hexahydrate, showed that the radiative energy migration (self-absorption) phenomena is the main responsible for the observed variations in t and in the relative intensities of the time-resolved vibronic electronic transitions. The second study, on potassium uranyl nitrate trihydrate at liquid nitrogen temperature, showed that the luminescence spectra is characterized by a vibronic progression in the symmetric stretching mode of the uranyl ion. The luminescence decay curves could be described as a bi-exponential function and two mechanisms were proposed to account for the experimental results.

ASSUNTO(S)

fisico-quimica analise espectral espectroscopia de luminescencia

ACESSO AO ARTIGO

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