Collective excitations built on the 2+γ state in 168Er

To examine the collectivity of the previously proposed Kπ=4+γγ-two-phonon state in 168Er at an excitation energy of 2056 keV and of the first excited Kπ=0+ band at 1217 keV (b-band), a Coulomb excitation experiment has been carried out at the Heidelberg-Darmstadt Crystal Ball spectrometer. The B(E2) value connecting the 4+γγ state to the γ-band was remeasured to be B(E2,4+γγ→2+γ)=(600±130)e2f m4, which almost exhausts the harmonic expectation. In addition, the B(E2) values connecting the band head of the lowest lying excited 0+b band to the 2+g and 2+γ states were measured to be B(E2,2+g→0+b)=(4.4±0.6)e2fm4 and B(E2,2+γ→ 0+b)=(30.4±4.6)e2fm4; the latter is almost a factor of 10 smaller than the B(E2,2+γ→0+g) value, which shows that the 0+b band head has no significant contribution of the Kπ=0+γγ-two-phon on state in its wave function. (orig.)