The penetration and concentration of solvated electrons and hydroxyl radicals at a plasma-liquid interface

In this work, we present an analytic model for the interfacial behavior of hydroxyl radicals (OHaq) and solvated electrons (e(aq)(-) ) delivered into an aqueous solution by an atmospheric pressure low-temperature plasma. The model yields simple scaling laws for the interfacial concentration and average penetration depth into the solution in terms of a few key operational parameters. Notably, the interfacial flux of free radicals is shown to be a key parameter, and the penetration of radicals into solution is shown to decrease as the radical flux increases. Additionally, the model sets upper limits for the average penetration on the order of 100 nm and interfacial concentration on the order of 1 mM (10(17) cm(-3)).