MEASUREMENT OF THE ROTATIONAL TEMPERATURE OF OXYGEN IN A HIGH-POWER INDUCTIVELY-COUPLED PLASMA

In a high-power (30 kW), inductively coupled argon-oxygen plasma used as a tool to deposit high-temperature superconducting YBa2Cu3O7-x film s rotational bands of the Schumann-Runge system B-3 Sigma(u)-X(3) Sigm a(g) Of oxygen were detected in the spectral regions around 340 and 36 0 nm. After derivation of the line strength factors for the triplet sy stem, rotational temperatures can be determined by fitting calculated relative intensities to those observed experimentally, and the contrib utions of R and P branches to the lines observed can be identified. Th e rotational temperature T at a distance of 34.5 cm from the exit of t he plasma torch where the deposition of superconducting films takes pl ace lies in the range 1850-2050 K depending on the RF power input whic h was varied in the range 8-27 kW. Near the torch exit, temperatures i n the range 2600-3400 K are observed. They depend strongly on gas comp osition and gas flow rate, in contrast to positions far away from the torch exit. Excitation temperatures near the torch exit which were der ived from Ar lines are considerably higher than the rotational tempera tures, indicating that the latter are typical of the colder outer part s of the plasma.