Positronium formation and inhibition in binary solid solutions on Al(III) and Co(III) tris(acetylacetonates)

Positron annihilation lifetime spectroscopy has been applied in mixtures and in solutions of solid Al(III), Al(acac) 3, and Co(III), Co(acac) 3, tris(acetylacetonates). For the solid solutions of Co(acac) 3 in Al(acac) 3, a strong inhibition of positronium formation is observed with increasing cobalt complex concentration, while there is no quenching of the positronium lifetime. In the solid mixtures the positronium formation probability decreases linearly with Co(acac) 3 concentration, while the positronium lifetime remains constant. The free volume model appears inadequate to explain the experimental results which are satisfactorily understood on the basis of the spur model.