Evolution of chirality from γ Soft 108Ru to triaxial 110,112Ru

Rotational bands in Ru-108,Ru-110,Ru-112 have been investigated by means of gamma-gamma-gamma and gamma-gamma(theta) coincidences of prompt gamma rays emitted in the spontaneous fission of Cf-252. The positive parity bands are described by different versions of IBA, where Ru-108 is best described as a gamma-soft nucleus whereas Ru-110,Ru-112 these are more like rigid triaxial rotors. New Delta I = 1 negative parity doublet bands are found. In case of Ru-110,Ru-112, these are interpreted as soft chiral vibrations. Many of the experimental findings can be explained by microscopic calculations that combine the TAC mean-field with random phase approximation but a simple geometrical explanation is not apparent. (C) 2008 Elsevier B.V. All rights reserved.