LASER-PARTICULATE INTERACTIONS IN A DUSTY RF PLASMA

The interaction of particulates formed in an argon RF discharge contai ning 1-5% CCl2F2 admixture with a pulsed infrared laser (Nd:YAG, inten sity approximately 10(9) W . m-2, pulse duration approximately 10(-4) s) has been studied in situ. The white light emitted during this proce ss has been monitored as a function of time and wavelength using a fas t photo diode and an optical multichannel analyser. The spectra have b een fitted with blackbody curves with a standard deviation of 5 %. A s pectral temperature of about 3500 K has been obtained for various plas ma conditions and attributed to the decomposition temperature of the p articulate material. A model based on laser heating, internal heat con duction and chemical decomposition is compared with the experimental r esults. This model predicts the time constants for heating and decompo sition of the particulates and explains the dependence of the measured emission intensity on the laser intensity.