ABSTRACT
This chapter describes fundamental plasma properties of nonthermal plasmas and introduces suitable diagnostic techniques. Elastic scattering of light on electrons is considered the gold standard of electron diagnostics in low temperature plasmas. Radiative energy transitions of species in a plasma can be probed by spectroscopy. With known quenching coefficients and quenching species, quencher-densities can be determined as is, for example, the case for water concentration in plasma jets over a water surface. The chapter also describes the physics background for spectroscopic analysis of plasma properties. These techniques range from optical emission spectroscopy, laser methods such as laser induced fluorescence techniques, scattering techniques such as Rayleigh-, Raman-, and Thomson scattering. The techniques also include optical absorption spectroscopy measurements to techniques known from chemical analysis such as mass spectrometry, gas chromatography, or electron paramagnetic resonance spectroscopy. Optical emission spectroscopy probes excited species in a plasma.
