Quenching of Positronium Lifetimes by Molecular Iodine

Abstract

Measurements of the mean life of the ${\tau }_2$ component for decay in solutions of iodine in normal heptane give a value of ${10}^{-17\mathrm{}}$ ${\mathrm{cm}}^2$ for the cross section of molecular iodine for annihilating ${}_{}{}^3{}_{}{}^{}S$ 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 ${\tau }_2$ from 2.49×${10}^{-9\mathrm{}}$ sec to 1.32×${10}^{-9\mathrm{}}$ sec the intensity $I_2$ of the long component was observed to vary over a range from 40% to 27%; however, the errors in $I_2$ are so large for the shorter lifetimes that it is impossible to tell from the data whether or not $I_2$ is influenced by the presence of iodine.