Diagnostics in a High-Flow-Rate (>6 L min −1 ) Helium Capacitively Coupled Microwave Plasma: Aqueous versus Organic Solution

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 ( T exc ), rotational ( T rot ), and ionization-recombination ( T ion ) temperatures were determined, along with the electron number density ( n e ). T exc was calculated from the slope of the Boltzmann plot with the use of Fe as the thermometric species. Values for T exc in aqueous and organic solution were 3430 and 3450 K, respectively. T rot determined with the use of both OH and N 2 + . With OH, T rot values were 1620 and 1660 K for aqueous and organic solutions, respectively. If no solution was introduced, a T rot value of 2350 K was determined with N 2 + . N 2 + also gave T rot values of 1900 and 1930 K with aqueous and organic solutions, respectively. The T ion values were 6220 and 5610 K with the use Cd and Mg, respectively. The n e value was on the order of 4 × 10 14 cm −3 . Background spectra and limits of detection are also presented.