Role of hydrogen in the ionization and enhancement of argon ions in a microwave plasma

Abstract

The effect of adding hydrogen gas in a microwave-induced argon plasma was studied using optical emission spectroscopy (OES) to determine the role of the hydrogen gas in the ionization and enhancement (increase of excited and ionized plasma species) of argon atoms. Spectroscopy data from the visible optical emission of the argon plasma gathered from the experiment were analyzed. Neutral and ion species (argon and hydrogen) in the plasma were identified using the Table of Line Spectra of Elements and the NIST Atomic Transition Probability Table of the CRC Handbook of Chemistry and Physics. The OES spectrograph analysis of the argon plasma showed a vast species of excited argon atoms (ArI). The excited state of hydrogen, H_α, was also evident when hydrogen gas is added to the plasma. The electrons, e_i, of the excited hydrogen atoms provide the impact electrons to produce argon ions (ArII or Ar⁺) and probably higher order ions (ArIII or Ar²⁺) by electron impact process on already excited or already ionized argon atoms. This study will pave the way to better understanding of the microwave plasma source used in the experimental results.