Radiation of metal atoms in the plasma of an atmospheric pressure glow discharge with an electrolyte cathode

The radiation of atoms of lithium (λ = 670 nm), sodium (λ = 588–589 nm), and calcium (λ = 657.2 nm, triplet) in an atmospheric pressure glow discharge plasma when the solution of the salt of the respective metal serves as a cathode is experimentally studied. It is shown that, in a system with solution circulation, the intensity of the mentioned lines during the discharge burning process rises tending to a constant limit value. The characteristic time of the establishing of the radiation intensity asymptotic value for the solutions of lithium, sodium, and calcium salts is 22, 5.5, and 9.5 minutes, respectively. These variations correlate with the previously observed growth of the rate of the nonequilibrium transfer of the solution components into the plasma zone. It is also found that the relationship between the line intensity and the discharge current is characterized by the presence of the threshold current (10–15 mA). The transfer from an alkaline solution to an acid one is attended with an increase of the intensity of the radiation of metal atoms.