Confirmation of irregular signature splitting in ⁷⁴As

Most odd-odd nuclei in the mass A ~ 70 region exhibit a consistent alternating pattern in the energy differences between adjacent states (signature splitting) in their strongest positive-parity bands.  In odd-odd ⁷⁴As, the pattern shows an irregular phase reversal at high spin, which has been attributed to the onset of an unpaired band crossing with an underlying triaxial deformation. However, this interpretation depends critically on the behavior of the signature-splitting pattern, which is based on uncertain spin assignments. The motivation for this study was to make firm spin assignments in the strongest positive-parity band of ⁷⁴As. High-spin states in ⁷⁴As were produced using the ¹⁴C(⁶²Ni, pn) reaction with a beam energy of 50 MeV at Florida State University. γ-γ coincidences were measured using a Compton-suppressed Ge detector array comprised of three Clover detectors and seven single-crystal detectors. Measurements of directional correlation of oriented nuclei (DCO) ratios were used to confirm most of the spin assignments in the strongest positive-parity band, supporting the interpretations of previous work.