Plasma diagnostic on a low-flow plasma for inductively coupled plasma optical emission spectrometry

In order to elucidate the fundamental properties of a low-flow inductively coupled plasma (ICP) operated under total Ar consumption of 0.6 L min− 1, excitation temperatures, rotational temperatures, ionization temperatures, electron temperatures, and electron number densities were studied with optical emission based methods. The plasma was operated in the SHIP torch (Static High Sensitivity ICP), which was designed for optical emission spectrometric detection.For the first time, this plasma was studied in a laterally resolved manner and at selected observation heights. The Boltzmann plot method was used to obtain excitation and rotational temperatures in the range of 5000–8000 K and 3100–4000 K, respectively. Electron temperatures were determined from the line-to-continuum method to be as high as 9000 K in the analytical channel. The electron number densities were determined with the hydrogen-beta line method and found to be in the range of 5–8 × 1015 cm− 3 at 1.1 kW radio frequency (rf) power. Ionization temperatures between 6250 and 7750 K were found at different observation heights in the plasma. The influence of applied rf powers between 0.9 and 1.2 kW on selected key parameters was investigated. The low-flow plasma exhibited temperature ranges similar to those prevailing in conventional ICP sources.