Spatial distribution of nonemissive metastables in a two-frequency capacitively coupled plasma in Ar by using a pair of optical emission lines

When a pair of short- and long-lived excited molecules are coupled with an upper radiative state, it will be possible to derive the number density of the long-lived species from the optical emission spectroscopy of upper-level short-lived species by careful selection of the pair. Two-dimensional density distributions of the long-lived metastable state Ar (1 s₅) and that of the short-lived excited state Ar (2 p₂) are observed and compared in the time-averaged form, using a computerized tomography technique of the emissions from a pair of optical transitions in a two-frequency capacitively coupled plasma in pure Ar.