K-shell ionisation in the positron decay branch of 68Ga

The number of K-shell vacancies produced per positron emitted in the β+ decay branch of 68Ga has been found to be (10.3 +- 1.0) x 10-4. This is 50% higher than the prediction of the theory of Law and Suzuki (1982 Phys. Rev. C 25, 514), which has proved successful in β- decay, and confirms the trend of the experimental results obtained in the three other positron decays which have so far been investigated. The importance of the final-state interaction in β+ decay has recently been shown theoretically by other authors, and a successful theory will probably require a combination of their approach with that of Law and Suzuki, which emphasises many-body effects. (author)