Comparative studies of time differential and integral directional correlation methods on delayed γ-ray cascades

Abstract

A time differential directional correlation method using a slow-fast coincidence setup consisting of four BaF 2 detectors was applied to measure the anisotropy of a number of γ-ray cascades in the β decay of 140La and the EC decay of 75Se. Such a four-detector arrangement combined with a proper data reduction method makes it possible to accurately separate prompt, random and delayed events, and to eliminate instrumental effects such as detector efficiencies to a large extent. In addition, hyperfine interaction attenuation could be accurately corrected for. Accordingly the achieved results: A 22(329–487) = −0.109(4) A 22(329–1596) = −0.103(3) and A 22(433–487) = +0.168(12) for 140 Ce and A 22(121–280) = −0.431(10) for 75 As are considered to be more reliable than values previously determined by means of conventional time integral methods.