Directional correlation measurements of the gamma rays emitted in the decay of 160Tb

Abstract

The decay of 160Tb to levels in 160Dy has been investigated by measuring the gammagamma directional correlations using two 30 cm 3 coaxial Ge(Li) detectors in conjunction with multichannel coincidence and routing electronics. A detailed analysis was performed in order to correct for the effects on the measured correlations of Compton-scattered radiation. The results of the sixteen measured directional correlations served to verify the current spin assignments, and in addition yielded values for the E2 M1 and M2 E1 multipole mixing ratios of the gamma transitions, given in terms of explicitly defined reduced matrix elements. Values obtained for the mixing ratios δ( γ) are (energies in keV): δ(215) = − 0.18 ± 0.10, δ(299) = + 0.005 ± 0.010, δ(392) = + 0.005 ± 0.070, δ(765) = − (7 +20 − 5), δ(879) = − 11.5 ± 1.9, δ(962) = − 18.0 ± 5.0, δ(1178) = + 0.02 ± 0.02, δ(1272) = − 0.03 ± 0.03. The results are discussed in terms of collective rotational nuclear motion.