Atomic and Molecular Fluorescence Spectrometry

Laser-induced Atomic and Molecular Fluorescence Spectrometry 

Principles and Characteristics The analytical capabilities of the conventional fluorescence (CF) technique (c/r. Chp. 1.4.2) are enhanced by the use of lasers as excitation sources. These allow precise activation of fluorophores with finely tuned laser-induced emission. The laser provides a very selective means of populating excited states and the study of the spectra of radiation emitted as these states decay is generally known as laser-induced fluorescence (LIF, either atomic or molecular fluorescence) [105] or laser-excited atomic fluorescence spectrometry (LEAFS). In LIF an absorption spectrum is obtained by measuring the excitation spectrum for creating fluorescing excited state 

At low laser intensities, the processes of laser-induced excitation and subsequent fluorescence are simply related for each laser photon absorbed an atom, ion or molecule is excited, and there is a constant probability that the subsequent decay will be via spontaneous radiation of a fluorescence photon. Provided that the sample is optically thin, the ratio of fluorescent signal to laser intensity will hence give the absolute species concentration. This is the basis of absolute measurements by LIF. However, at high laser intensities, typical of pulsed excitation, saturation occurs. 

Laser-induced atomic fluorescence is increasingly being used for trace elemental analysis. Despite the monochromaticity of laser radiation the 

In general, the accuracy of LEAFS is to be assessed by comparison to standard reference materials (SRM s) but is usually very good. The technique [113,114] shows freedom from spectral interferences, low matrix effects and a linear dynamic range of 5-7 orders of magnitude. With ETA-LEAFS, direct solid analysis is a fast, safe and accurate means to analyse polymers compared with methods that require difficult and time-consuming dissolution procedures. A major drawback inherent with ETA-LEAFS and ETAAS is the single-element capability. 

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Laser-induced Atomic and Molecular Fluorescence Spectrometry.343... 

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