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

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 K^π=0⁺ ("quasi"-β) and the K^π=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.