Abstract

A helium capacitively coupled microwave plasma (CMP) with a high plasma gas flow rate (>6 L min^-1) is described. Plasma gas flow rates above 6-8 L min^-1 produce a cylindrical-shaped plasma. Diagnostic studies were performed. Electronic excitation (<i>T</i>_exc), rotational (<i>T</i>_rot), and ionization-recombination (<i>T</i>_ion) temperatures were determined, along with the electron number density (<i>n</i>_e). <i>T</i>_exc was calculated from the slope of the Boltzmann plot with the use of Fe as the thermometric species. Values for <i>T</i>_exc in aqueous and organic solution were 3430 and 3450 K, respectively. <i>T</i>_rot determined with the use of both OH and N₂⁺. With OH, <i>T</i>_rot values were 1620 and 1660 K for aqueous and organic solutions, respectively. If no solution was introduced, a <i>T</i>_rot value of 2350 K was determined with N₂⁺. N₂⁺ also gave <i>T</i>_rot values of 1900 and 1930 K with aqueous and organic solutions, respectively. The <i>T</i>_ion values were 6220 and 5610 K with the use Cd and Mg, respectively. The <i>n</i>_c value was on the order of 4 × 10¹⁴ cm^-3. Background spectra and limits of detection are also presented.

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