Spectral excitation of dielectric matrix trace atomic and molecular species by atmospheric pressure sliding spark plasma
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The goal of this work was to investigate the potential of sliding spark plasma to excite from dielectrics emission spectra that have utility in direct trace quantitative analysis of non-conducting materials in air at atmospheric pressure. The sliding spark is a special variety of pulsed plasma specularly discharging across a dielectric surface enforced between a pair of electrodes. Analysis of the emission spectra measured between 212 ≤ λ ≤ 511 nm using CCD spectrometer showed that the sliding spark is accompanied by prompt atomic and molecular emission over a broad wavelength range. Each dielectric is characterized by unique spectral features composed of mostly overlapping atomic, ionic and molecular lines and a complex background that results from the plasma species, cathode material, operating environment and the major components of the sample matrix including their reaction products. Among the measured lines a number (depending on the oxidation state of the element in the matrix) of atomic and ionic lines were found to be free from spectral interference and with good signal-to-noise ratio, which indicates their potential for direct trace quantitative analysis utilizing a new technique: sliding spark spectroscopy. Mostly ionic lines are optically thin. In the UV range the lines are especially not broadened and are identifiable against a weak continuum.