Mean Lives of Positrons in Aqueous Solutions

Abstract

By measurement of the time distribution of positron annihilations in aqueous solutions, reaction rates for oxidation of positronium by the ions MnO4—, IO3—, and Hg++ have been determined. In strong oxidizing solutions the mean life of the positrons reaches a lower limit of 4.3×10—10 sec; the short lifetime τ1 in water was measured and found to agree with this value. A Pb(ClO4)2·3H2O solution reduced the intensity I2 with no significant change in the long life τ2, an effect previously observed in nitrate solutions. This may mean that in these two cases oxidation can occur before Ps is thermalized but not afterwards. The decay distributions from a mixture of Hg++ and MnO4— ions in solution and the Hg++ ion in separate solutions with Cl— and ClO4— indicated an association taking place between the negative and positive ions.