Annihilation of Positrons in Organic Compounds

The mean life ${\tau }_2$ and the fraction $I_2$ of positrons which decay with a "long" ${10}^{-9\mathrm{}}$-sec lifetime have been measured in several organic compounds, most of which are derivatives of benezene. For the long components observed in liquids ${\tau }_2$ ranges from 1.6×${10}^{-9\mathrm{}}$ sec to 2.5×${10}^{-9\mathrm{}}$ sec, whereas $I_2$ varies from 35% to 4%. A correlation between $I_2$ and certain properties of the molecules indicates a qualitative explanation of the results.