The level structure of 156Gd studied by means of the (α, 2nγ) reaction

Abstract

A complete set of conventional γ-ray spectroscopic techniques has been applied to investigate the level structure of 156Gd. A total of twenty-five new levels has been established; unambiguous spin assignments could be given for twelve of them on the basis of angular distributions and conversion electron measurements. The proposed level scheme contains 49 levels, which can be ordered in seven rotational bands. The ground-state band was excited up to J π = 14 +, the β-band up to 10 +, the γ-band up to (11 +), the second K π = 0 + band tentatively up to (10 +), the K π = 4 + band up to (8 +). Two negative-parity bands, one with even spins and one with odd spins, were excited to J π = (12 −) and (13 −). An isomeric state was established with T 1 2 = 1.3 μs, J π = 7 −, E x = 2137.7 keV . The properties of the K π = 4 + band and the isomeric state can be well explained by two-quasiparticle configurations. The negative-parity bands are interpreted as aligned octupole bands. Positive and negative-parity bands have been calculated in terms of the IBA model. Good agreement with the experimental results is obtained.