Optical Emission and Parameters of Dielectric Barrier Discharge Plasma In A Mixture of Mercury Diiodide and Mercury Dibromide Vapor With Helium

摘要

The spectral, energy and electrical characteristics of the plasma of a dielectric barrier atmospheric pressure nanosecond discharge on a mixture HgI_(2)/HgBr_(2)/He are investigated. The discharge was initiated by a pulse-periodic voltage with a pulse repetition rate 5-20 kHz of positive polarity, an amplitude 25.5 kV, and a half-height duration 150 ns. The emission of exciplex molecules HgI (B~(2)Σ~(+)_(1/2)-X~(2)Σ~(+)_(1/2)) and HgBr (B~(2)Σ~(+)_(1/2)-X~(2)Σ~(+)_(1/2)) was studied. Based on a comparison of the temporal behavior of the spectra of B-X transitions of HgI, 444 nm, and HgBr, 502 nm molecules, the mechanism of simultaneous formation of the exciplex molecules HgI* and HgBr* is determined. Based on the numerical solution of the Boltzmann equation for the electron energy distribution function, the energy and velocity distributions of the processes responsible for the emission of HgI and HgBr molecules are analyzed. The studies revealed the possibility of optimizing the pulsed power to obtain a simultaneous emission in the visible (violet-blue and blue-green light) spectral range in atmospheric pressure discharge in the HgI_(2)/HgBr_(2)/He mixture. When a short powerful pulse of several nanoseconds in duration (3-5) ns is used to obtain a relatively high initial ion ionization (10~(12)-10~(13) cm~(-3)), followed by a long pulse of tens or hundreds of nanoseconds, depending on the component composition of the mixture and pressure with relatively low electric fields, a mixed power source will ensure efficient excitation of HgI* and HgBr* molecules and may be the optimal solution for the discharge lamps based on HgI* and HgBr* emission.