MECHANISTIC STUDIES OF LASER-INDUCED BREAKDOWN SPECTROSCOPY OF MODEL ENVIRONMENTAL-SAMPLES

We examine a number of factors which influence the use of laser-induce d breakdown spectroscopy (LIES) to detect the cation content of physic al mixtures of Eu2O3 and K2Cr2O7 with granular, crystalline SiO2. Exci tation of the powdered specimens is by focused KrF excimer laser light (248 nm, 30 ns pulse width, fluence/pulse 0.3-30 J cm(-2), irradiance 10-1000 Mw cm(-2)) in 1 atm air. We discuss the resulting time resolv ed UV/vis spectra of the plasma, the parameters and physical effects w hich influence the detection of impurities and examine the consequence s of the presence of water in the samples together with variations in the sample morphology. We also present preliminary results on spectra from mixtures of these compounds with a basaltic soil.