Low-spin non-yrast states in light tungsten isotopes and the evolution of shape coexistence Original Research Article

Excited states in 170W, 172W, 174W, 176W and 178W have been populated in the β-decay of 170–178Re isotopes and studied using γ-ray singles and coincidence techniques, utilising the high efficiency of a Compton-suppressed array, and conversion electron systems. Many new states at low excitation energies have been identified, complementing the level schemes previously established from in-beam studies. A large body of data on decay properties, spins and parities, and relative E2 and E0 matrix elements has been obtained. The properties of the Kπ=0+ (“quasi”-β) and the Kπ=2+ (“quasi”-γ) bands are compared with similar bands observed in light osmium, platinum and mercury isotopes, where shape coexistence has been established at low spin.