Spatially Resolved Oxygen Dissociation and Thermometry of an Atmospheric Ar/O 2 Plasma Using Ultrafast CARS

Simultaneous detection and point-wise radial profiling of O and O2 in a newly developed 1 kW atmospheric inductively coupled plasma (ICP) is demonstrated using an ultrafast pure-rotational coherent anti-Stokes scattering scheme. Running an Ar/O2 mixture containing 14.2 vol% O2, radial line profiles were acquired approximately one torch diameter downstream of the nozzle exit at 600, 750, and 900Wof applied RF power. Atomic oxygen is found to dominate core of the jet at higher powers, transitioning to a mixture of atomic and molecular species near the sheath. Pure rotational O2 CARS thermometry is used to estimate radial bulk temperatures, exhibiting classical ICP thermal stratification profiles while peaking at 3859 K for the 600W condition and exceeding 4200 K in the higher power cases.