Spectroscopic techniques for the characterisation of spectrochemical plasma sources

In spectrochemistry, various plasma sources are used for the analysis of sa mples. The simplest way to characterise these plasma sources is to determin e the absolute intensities of several atomic lines of the main plasma gas ( argon or helium). From these measurements absolute population densities of excited states can be deduced and, via a so-called Boltzmann plot, the elec tron temperature T-e and density n(e). This method works quite well as long as the plasma is relatively close to equilibrium. The reason why spectroch emical plasmas can show strong deviations from equilibrium will be discusse d. An other limitation of emission spectroscopy is the lack of accurate tra nsition probabilities for transitions from highly excited states. For argon 15 of these probabilities have been determined with an uncertainty of +/-2 5%.