Levels in 161Tm excited in the decay of 4.2 min 161Yb

Abstract

The decay of 161Yb ( T 1 2 = 4.2 min ) has been investigated with Ge(Li) and Si(Li) detectors and a toroidal β-spectrometer. Isobarically separated samples produced by the YASNAPP facility at Dubna Institute were used. The singles γ-ray spectrum, the conversion electron spectrum, γ-γ-τ and e-γ coincidences have been measured. In all, 67 γ-ray transitions have been observed. A decay scheme for 161Yb is proposed involving 12 excited states in 161Tm. The 7 2 +[404], 7 2 −[523] and 5 2 +[402] levels have been identified. The interpretation of the high-lying levels is discussed. The Q-value of 161Yb decay has been determined to be 3850 ± 250 keV. The A-dependence of the energies of the one-quasiparticle states in odd- A Tm isotopes is demonstrated.