Electron-temperature and electron-density profiles in an atmospheric-pressure argon plasma jet

Line-shape analysis of the electron feature of Thomson-scattered laser light has been used to directly determine electron-temperature and electron-density profiles of an atmospheric-pressure argon plasma jet. Measured center line values of the electron temperature are in excess of 20 000 K at the torch exit, and remain essentially constant with increasing axial distance even though the plasma is recombining. These results are shown to be inconsistent with Saha equilibrium and classical electron-ion momentum transfer theory.