Multiple triaxial bands and abnormal signature inversion in As3374

Excited states of the odd-odd nucleus 74As have been investigated via heavy ion fusion evaporation reaction Zn70(Li7,3n)As74 at beam energy of 30 MeV. The properties of the positive- and the negative- parity bands can be interpreted in terms of the Cranked Nilsson-Strutinsky (CNS) model calculations which show that the observed bands are built on the triaxial deformed shape. The inversion of the favored and unfavored signature branches observed in the positive-parity bands presents at high spins rather than normal signature inversion occurs at low spins. This phenomenon may be explained as the origin of unpaired band crossing in a highly rotating triaxial nucleus.