Quenching of Positronium Lifetimes by Molecular Iodine

Measurements of the mean life of the τ₂ component for decay in solutions of iodine in normal heptane give a value of 10^-17 cm² for the cross section of molecular iodine for annihilating ³S positronium on collision. This effect is attributed to an enhancement of "pickoff" annihilation resulting from either a tendency to form positronium iodide or the high polarizability of molecular iodine. In quenching τ₂ from 2.49×{}10^-9 sec to 1.32×{}10^-9 sec the intensity I₂ of the long component was observed to vary over a range from 40% to 27%; however, the errors in I₂ are so large for the shorter lifetimes that it is impossible to tell from the data whether or not I₂ is influenced by the presence of iodine.