Search for tetrahedral bands in yb isotopes

Abstract

Calculations by Dudek et al. predict shell gaps for tetrahedrally shaped nuclei at various proton and neutron numbers. 160Yb is expected to be a favourable nucleus, with tetrahedral bands predicted to lie 1 MeV above the ground state. A search for such states has been performed using the Afrodite Ge detector array at iThemba LABS. A 73MeV 160 beam bombarded a 147Sm target of thickness 3mg/cm2 to produce 160Yb at low spin and high excitation energy. After analysis of the data, new rotational bands have been added to the level scheme. Although these bands are in the expected energy interval for the tetrahedral states, they do not show the expected decay properties of the tetrahedral bands. Rather, we interpret them as vibrational y and 13 bands.