Lifetime measurements of excited K^π=0⁺ bands in ¹⁷⁸Hf

Lifetimes of three excited Kπ=0+ bands have been measured in the same deformed nucleus (178Hf). Evidence is presented for the first observation of two excited Kπ=0+ bands connected via collective E2 transitions. Five-band mixing calculations show that these collective transitions are not the result of mixing between the various bands. It is therefore suggested that the Kπ=05+ band at 1772.2 keV is a collective excitation built on the single phonon Kπ=02+ band at 1199.4 keV.