A Long Period Positron Activity:Na22

Abstract

The bombardment of magnesium with 5.2 Mev deuterons was found to result in a long period radioactivity ascribable to ${\mathrm{Na}}^{22}$. The half-life, as determined from measurements extending over a period of a year, is 3.0±0.2 years. Absorption measurements on the positrons emitted agree with similar measurements made with a fluorine sample subjected to alpha-particle bombardment; the positron momentum distribution was investigated with a hydrogen-filled cloud chamber in a magnetic field, an upper limit being found at a value corresponding to 0.58±0.03 Mev.