Spectral excitation of dielectric matrix trace atomic and molecular species by atmospheric pressure sliding spark plasma

Abstract

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.