Cold atmospheric plasmas (CAPs) are a topic of growing interest nowadays, especially due to their applicability in material processing and biomedical applications. The laser scattering techniques of Thomson, Rayleigh and Raman provide precise measurements of the electron temperature, electron density, and the gas temperature. These laser scattering diagnostic methods are advantageous due to the high spatial and temporal resolution that they can achieve.
In this contribution we aim to address the possibilities of laser scattering techniques as well as the main complications that come into play when they are applied to cold atmospheric discharges. A classical problem for Thomson scattering experiments is the false stray light, which might deteriorate the detection limit. As a consequence of their low gas temperature and open air operation, CAPs present high concentrations of molecules. This implies that the Thomson and Raman spectra will overlap, and therefore the two signals must be precisely disentangled. Another characteristic of CAPs is the low ionization degree which can induce deviations in the electron energy distribution function (EEDF). These deviations mainly affect the tail of the EEDF. An energy region that is not easy to measure by Thomson scattering. Finally, the laser heating of the electron gas is another issue which has to be considered. In the case of CAPs the contribution to the laser-heating intermediated by electron-atom collisions cannot be neglected.
To place the specific features of laser scattering techniques in a broader perspective we will compare the CAP results to those obtained on low pressure plasmas
