Ortho–para conversion of positronium in some rare-earth ion aqueous solutions

Abstract

We have extended a previous investigation by studying the ortho–para conversion of positronium in aqueous solutions of some lanthanide ions (Yb3+, Tm3+, Er3+, Dy3+, and Tb3+). The corresponding cross sections were found to be proportional to the number of unpaired electrons in the ion. Furthermore, the contact density of the electron–positron pair in the origin was obtained for a 1 M aqueous solution of ErCl3.