A spectrometric study of a 40 MHz inductively coupled plasma—VI: Argon continuum in the visible region of the spectrum

The nature of a pure Ar continuum observed in ICP-AES has been studied in the 400–700 nm range. The radiative recombination is predominant below 500 nm, but bremsstrahlung must be considered above 500 nm. The electron temperature T_e deduced from the ratio of an Ar line to the adjacent continuum is about 10,000 K, which is significantly different from the excitation temperatures previously measured in this source. The electron number density (n_e) determined from the continuum is in good agreement with the value determined from the Stark effect on Ar 1549.5 nm line and about 5 × 10²⁰ m^?3. The continuum varies with the input power and the carrier gas flow rate. This is mainly due to the variation of n_e.