Gating on the feeding or on the depopulating transition in coincidence recoil-distance Doppler-shift lifetime measurements

Two alternative ways of setting gates and lifetime determination in coincidence RDDS measurements are investigated for the case of two consecutive γ-ray transitions. Assuming a very general perturbed angular correlation function, it is shown that only the approach where the gate is set on the flight peak of the feeding transition gives results which are not influenced by the hyperfine interactions.