Time- and space-resolved measurements of Ar(1s₅) metastable density in a microplasma using diode laser absorption spectroscopy

Abstract

Time- and space-resolved measurements of Ar(1s 5 ) metastable (Ar*) density were carried out in a pulsed dc argon microplasma discharge, using diode laser absorption spectroscopy. The temporal behaviour of metastable density after discharge turn off (in the afterglow) depended on their spatial location in the microplasma. In the early afterglow, the Ar* density decayed monotonically with time in the region around the sheath edge, while in the bulk plasma the Ar* density showed a maximum with time. This behaviour was attributed to electron–ion dissociative recombination. Later in the afterglow, the Ar* decay was everywhere monotonic with time, mainly due to three-body collisional quenching by ground state argon atoms. The time evolution of the Ar* density in the afterglow predicted by a kinetic model is in good agreement with the experimental measurements.