On the inhibition of positronium formation in ethylenediamine and liquid ammonia solutions of NO 3− ions

Abstract

It is well known that the Ps formation is inhibited in water solutions of NO 3 − ions. Several models were advanced in order to explain the phenomenon (competition between the Ps and the e +NO 3 − formations; narrowing of the Ore gap by excited levels of NO 3 − ions; hot Ps reactions with NO 3 − ions; competition between NO 3 − ions and e + for electrons of the positron spur). With the hope to give a contribute to a better understanding of the phenomenon, the Ps inhibition by NO 3 − ions was reinvestigated in aqueous solutions and studied in liquid ammonia and en (ethylenediamine). The results obtained were examinated on the light of the models previously discussed. It was concluded that while the hypotheses of the formation of the e +NO 3 − compound and of the narrowing of the Ore gap must be discarded and the spur model does not seem at present full refined, on the contrary the hot reactions model offers a simpler explanation for the dependence of the inhibition of Ps formation on the NO 3 − concentration. A new equation relating the Ps formation I(o-Ps) to the inhibitor concentration was deduced. This equation allows us to advance some predictions, inter alia the behaviour of the positronium inhibition in solvent mixtures can be inferred.