Comparison Among Translational Temperatures Of He(P-1(1)O), He(S-3(1)), And Ar(4s [3/2](2)(O)) In Inductively Coupled Plasmas

We compared the translational temperatures of He(P-1(1)o), He(S-3(1)), and Ar(4s [3/2](2)(o)) in low-pressure inductively coupled plasmas. We employed laser absorption spectroscopy for measuring the Doppler broadening widths of the transition lines, and they told us the translational temperatures of the three electronic excited states. From the comparison between the temperatures of He(P-1(1)o) and He(S-3(1)), we confirmed that the metastable S-3(1) state can work as the probe for the temperature measurement of the ground state helium atoms. We observed higher temperatures for Ar(4s [3/2](2)(o)) than He(S-3(1)) in helium-argon mixture plasmas with total pressures less than 80 mTorr. The higher Ar(4s [3/2](2)(o)) temperature is considered to be due to the selective heating of argon by the charge exchange collision with Ar+. (C) 2021 The Japan Society of Applied Physics