In a high-power, inductively coupled argon-oxygen plasma used to deposit high-temperature superconducting YBa2Cu307-x films rotational bands of the Schumann-Runge system B 3Σu− − X 3Σg− of O2 were detected around λ= 350 nm. After derivation of the line strength factors for the triplet
system rotational temperatures were determined by fitting calculated relative intensities to those observed experimentally, and the contributions of R- and
P-branches to the lines observed could be identified. The rotational temperature at the position where the deposition of superconducting films takes place lies between 1850 and 2050 K depending on the power input which was varied from 8 to 27 kW. Near the torch exit temperatures from 2600 to 3400 K are found. They depend strongly on gas composition and flow rate, in contrast to positions far away from the torch exit. Excitation temperatures near the torch exit derived from Ar lines are considerably higher than the rotational temperatures, indicating that the latter are typical of the colder outer parts of the plasma.