Yrare low-spin positive-parity states in N = 88 ₆₆¹⁵⁴ Dy

Low-spin positive-parity yrare states of ₆₆¹⁵⁴Dy₈₈ were established using the ¹⁵⁵Gd(³He,4n) reaction at a beam energy of E_lab= 37. 5 MeV. The AFRODITE spectrometer array at iThemba LABS was used to record γγ coincidences and measure DCO ratios and polarisation asymmetries. The K^π= 2 ⁺γ band has been observed up to spin 13 ⁺ in the odd spins and to 12 ⁺ in the even spins. The staggering parameter S(I) of the γ band is compared to that found in other N = 88 isotones. Different behaviour of S(I) with increasing spin is observed for each of the isotones. We conjecture that the variation in S(I) is mainly due to mixing of the even-spin states with the same spin and parity states in neighbouring rotational bands. A second K^π= 2 ⁺ band has been established up to a spin of 12 ⁺ in the even spins. We suggest that this is a γ band based on the J^π= 0 ⁺ state at E_x= 660. 6 keV.