Measurements of the total energy lost per electron–ion pair lost in low-pressure inductive argon, helium, oxygen and nitrogen discharge

Experimental measurements of the total energy lost per electron–ion pair lost, eT, were performed in a low-pressure inductive atomic gases (Ar, He) and molecular gases (O2, N2) discharge. The value of eT was determined from a power balance based on the electropositive global (volume-averaged) model. A floating harmonic method was employed to measure ion fluxes and electron temperatures at the discharge wall. In the pressure range 5–50 mTorr, it was found that the measured eT ranged from about 70 to 150 V for atomic gases, but from about 180 to 1300 V for molecular gases. This difference between atomic and molecular discharge is caused by additional collisional energy losses of molecular gases. For argon discharge, the stepwise ionization effect on eT was observed at relatively high pressures. For different gases, the measured eT was evaluated with respect to the electron temperature, and then compared with the calculation results, which were derived from collisional and kinetic energy loss. The measured eT and their calculations showed reasonable agreement.