Mechanism of Spectrum Excitation in a Solid Aerosol-Laden Plasma Jet of a Two-Jet Argon Arc Plasmatron

A possible reason for the high intensity of the ion emission in the spectrum excitation in a plasma jet generated by a two-jet argon arc plasmatron was considered. The injection of a test substance as an air–solid suspension between the plasma jets (i.e., mixing of a hot plasma with a cold directional carrier-gas flow) created a radial temperature gradient and induced an intense argon influx from the dense plasma jets to the cold axial plasma zone used for analytical purposes. Favorable conditions were thus created for the analyte Penning impact ionization with argon ions. This was confirmed by the existence of a correlation between an increase in the intensity of ion lines with the carrier-gas flow rate (cooling rate) and the total energy of ionization and excitation of an element. It was shown that charge transfer from the argon ion to the analyte occurred only in the case when the total energy of the element was lower than 16 eV, i.e., lower than the ionization energy of argon plus its kinetic energy.