Electron Number Densities in Analytical Inductively Coupled Plasmas as Determined via Series Limit Line Merging

Abstract

A convenient and a rapid technique is introduced to estimate the electron number densities, n_e, in inductively coupled plasmas. The method is based on previously reported observations that the principal quantum number of the last discernible line in a series limit depends on n_e. The spatially integrated n_e values, as determined from the spectra of H, Li, Mg, Al, Ca, and K emitted in a pure Ar plasma ranged between ∼4 × 10¹⁴ and ∼3 × 10¹⁵ cm⁻³ for various forward powers and observation heights. These results agreed with n_e values derived from other methodologies such as the Stark broadening and absolute continuum intensity.