SPECTROSCOPIC TEMPERATURE-MEASUREMENTS IN OXYGEN DISCHARGES

The rotational temperature of the excited state O2 (b1-SIGMA-g+, v = O) in an oxygen glow discharge is measured from the intensity distribution of the atmosphereic A-band O2 (b1-SIGMA-g+, v = O) --> O2(X3-SIGMA-g-, v = 0) at lambda = 760 nm. The kinetic temperature, often called the gas temperature is also deduced using vacuum ultraviolet absorption spectroscopy in the same experimental conditions: pressure p = 0.5-5 torr, discharge current up to 100 mA and deposited power up to 2 W cm-1. It is shown that the rotational temperature of the A-band is equal to the rotational temperature of the molecular X3-SIGMA-g- ground state and of the first metastable a 1-DELTA-state measured by coherent anti-Stokes Raman spectroscopy. Since the kinetic temperature is in equilibrium with the rotational temperature of the ground state, we conclude that the rotational temperature of the O2 (b1-SIGMA-g+) state is identical to the gas temperature.