Positron annihilation in triphenylphosphine oxide complexes: Positronium inhibition mechanism involving excitation of charge transfer states

Positronium formation in triphenylphosphine oxide and its lanthanide and hydrogen peroxide complexes have been characterized. The low probability of positronium formation observed has been attributed to a mechanism involving competition between charge transfer at large distances induced by the positron-molecular electron interaction and positronium formation during positron molecule scattering. The molecular site responsible for positronium formation has been identified.