High-spin states in 218Ra

Yrast states in 218Ra up to spin and parity Iπ = 17− were identified by means of the 208Pb(13C, 3n) reaction and standard γ-ray spectroscopic techniques. The level scheme is characterized by two bands of opposite parity with nearly constant level spacing. A cascade of strong E1 interband transitions connects both bands. The results are discussed within the systematics of the even Ra isotopes. The negative-parity band which is observed from the Iπ = 5− to the Iπ = 17− state, is interpreted as an octupole vibrational band. The level scheme can be well reproduced in the vibrational limit of the interacting boson approximation (IBA1) which fails, however, to explain the strong E1 feeding of the negative-parity band from the ground-state band