Determination of the activity of 225 Ac and of the half-lives of 213 Po and 225 Ac.

The activity concentration of an 225Ac solution was determined by means of liquid scintillation counting using three custom-built TDCR counters. The efficiency calculation was carried out in the same way as it had been done in an earlier article on 229Th. The computation of the counting efficiency is rather complex and requires a correction to allow for the short-lived 213Po. The experimental deadtime was varied to validate the correction.