Temporal Evolution of Gas Temperature in the Afterglow of Pulsed ICP Discharge Using Rayleigh Scattering

A Rayleigh scattering technique was adopted in the current work to measure for the first time (to our knowledge) the temporal evolution of the gas temperature in the afterglow of low-pressure pulsed ICP discharge operated with argon and Ar/O2 (10 % O2) gases. For all gas compositions used in this work and for averaged applied RF power of 100 Watt, the gas temperature was found to be constant in the afterglow time period having a value of 350 K. By using averaged RF power of 500 Watt, the trends of the temporal evolution of the gas temperature and their values were found to be a function of the gas composition and its pressure. For gas pressure of 20 mTorr of pure argon and Ar/O2 (10% O2) admixture, the trends of gas temperature evolution were exponentially decaying with decaying time constant of 2.5 & 19 microseconds, respectively. For 100 mTorr of Ar/O2 (10% O2) a striking trend of the temporal evolution of the gas temperature was observed where the gas temperature was increasing in the afterglow period which might be ascribed to the increase of the electron temperature in the afterglow due to the transition of the deposited RF power from inductive mode to capacitive mode enhanced by vibrational ?rotational deexcitation of molecular oxygen.