Time-Resolved Characteristics of Atomic Emission Spectrum in Sodium-Argon Mixture after Ionization

Herein, the atomic emission spectrum of a sodium-argon mixture is obtained after ionization, and its time-resolved characteristics are experimentally studied. When observing the time-resolved evolution of argon spectral intensity at 763.5 nm, two peaks appear. The first peak with a decay time of (33.3±2.3) ns is observed via the fast radiation of particles at argon 2p6 state, which excited through collisional energy transfer from the excited sodium atom [time constant is (15.2±0.8) ns]. Following the recombination of argon ions and electrons, the second peak is observed; this peak's decay process contains both a fast [(0.24±0.03) μs] and a slow [(3.98±1.03) μs] steps. Using the evolution relationship of electron density with time, the mechanism for decay time, which is impacted by the recombination process, is analyzed. The evolution relationships of electron density and electron temperature with time are obtained. The time-resolved atomic emission spectrum can experimentally explain the unusual phenomenon of the obviously different broadening between the D1 and D2 lines of the sodium spectra; these reasons are the spectral line of argon at 588.9 nm overlaying the sodium D2 line (589.0 nm) after Stark broadening and the self-absorption on two D lines of the sodium. Because the energy level splitting is small for the excited argon atom after recombination, the particle population accumulated on the 2p6 state via cascade relaxation takes a shorter time than that on the sodium 3P state, and the duration of the argon atom emission spectrum is obviously shorter than that of the sodium atom. © 2019, Chinese Lasers Press. All right reserved.