  The electron and gas temperature of non-equilibrium argon plasma torch
sustained by a focused 24 GHz microwave beam in the external atmosphere of air
was measured by optical emission spectroscopy. The excitation temperature of
argon atoms was found about 5000 K, while the vibrational and rotational
temperatures of ambient nitrogen molecules were respectively estimated at 3000
K and 2000 K. The effective mixing of the external gas atmosphere into the
plasma torch is experimentally demonstrated. The vibrational and rotational
temperatures of nitrogen molecules slightly increased with the distance from
the nozzle exit. Experimental results demonstrate that microwave discharge at
atmospheric pressure may be relevant for the decomposition of highly stable
molecules, e.g. carbon dioxide, in non-equilibrium conditions.
