Electrochemical switching of positronium triplet quenching.

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 τm 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 τm which perfectly correlates with the shift between the reduction and oxidation peaks simultaneously monitored by cyclic voltametry.