Multi-band spectral structure and kinetics of the third continua in Ar,Kr and Xe gases excited by a pulsed discharge

Time-resolved VUV-UV emission of Ar, Kr, and Xe gases (Rg), excited by a pulsed discharge, have been measured to clarify the origin of the 3rd continua. Several detected continuum bands exhibit very different time behaviors due to various atomic (ionic) precursors and plasma kinetics. Imaging experiments with ns-gated ICCD camera have shown that the 2nd continua (Rg₂^*) and Rg^* lines emit uniformly in the positive column of the discharge. However, the 3rd continua and Rg^+* lines were excited exclusively in the negative glow zone, where high-energy electrons are injected from the cathode layer. The multi-band structure of the 3rd continua has been connected with Rg²⁺ ions produced in the ground and different excited states. These precursors lead to the formation of several bound states Rg₂^2+*, which decay radiatively to the repulsive states (Rg⁺ + Rg⁺), where Rg⁺ ions can be on ²P_3/2, ²P_1/2 levels due to spin-orbit coupling. The rate constants for the formation of Rg₂²⁺ excimers in three-body reaction and two-body collisional quenching of Rg^2+∗ ions have been determined from the time behaviors of emission. The quenching of Rg^2+∗ ions is explained by the level crossing between bound (Rg^2+* + Rg) and repulsive (Rg²⁺ + Rg) potential curves.