Spin dependence of K mixing, strong configuration mixing, and electromagnetic properties of ¹⁷⁸Hf

The combined data of two Coulomb excitation experiments has verified the purely electromagnetic population of the K^π=4⁺,6⁺,8^-, and 16⁺ rotational bands in ¹⁷⁸Hf via 2≤ν≤14 K-forbidden transitions, quantifying the breakdown of the K-selection rule with increasing spin in the low-K bands. The γ-, 4⁺, and 6⁺ bands were extended, and four new states in a rotational band were tentatively assigned to a previously known K^π=0⁺ band. The quasiparticle structure of the 6⁺ (t_1/2=77 ns) and 8^- (t_1/2=4 s) isomer bands were evaluated, showing that the gyromagnetic ratios of the 6⁺ isomer band are consistent with a pure π7/2⁺[404],π5/2⁺[402] structure. The 8^- isomer band at 1147 keV and the second 8^- band at 1479 keV, thought to be predominantly ν7/2^-[514],ν9/2⁺[624] and π9/2^-[514],π7/2⁺[404], respectively, are mixed to a degree approaching the strong-mixing limit. Based on measured 〈K^π=16⁺‖E2‖K^π=0⁺〉 matrix elements, it was shown that heavy-ion bombardment could depopulate the 16⁺ isomer at the ~1% level, although no states were found that would mediate photodeexcitation of the isomer via low-energy x-ray absorption.