Electrochemical switching of positronium triplet quenching

Abstract

Switching of positronium triplet quenching could successfully be demonstrated by electrochemical means in an aqueous K₃[Fe(CN)₆] electrolyte. For this purpose a suitable cell was designed to combine positron annihilation with electrochemical measurements. Highly reversible substantial variations of the mean positron lifetime τ_m could be observed upon electrochemical switching between the oxidation states Fe(CN)₆³⁻ and Fe(CN)₆⁴⁻, arising from oxidation of positronium by Fe(CN)₆³⁻. Dynamic in situ measurements in dependence of potential exhibit a hysteresis like behavior of τ_m which perfectly correlates with the shift between the reduction and oxidation peaks simultaneously monitored by cyclic voltametry.