Solid Eu(III) complexes studied by positron annihilation, optical and Mössbauer spectroscopies: Insights on the positronium formation mechanism

► Absence of positronium formation in europium complexes. ► Mössbauer, luminecence and positron spectroscopies measured in Eu(dpm)3. ► Discussion based on fast electron hopping, Eu(III) reduction and charge transfer. ► A possible mechanism for positronium formation is presented.