EPJ

2023 Impact factor 2.6
EPJ A - Hadrons and Nuclei
Hadrons and Nuclei
Eur. Phys. J. A 2, 253-261

Collective excitations built on the ${\bf 2^+_\gamma}$ state in 168Er

T. Härtlein1 - M. Heinebrodt1 - D. Schwalm1 - C. Fahlander2

1 Max-Planck-Institut für Kernphysik, D-69117 Heidelberg, Germany
2 Division of Cosmic and Subatomic Physics, Lund University, S-22100 Lund, Sweden

Received: 25 February 1998 Communicated by B. Povh

Abstract
To examine the collectivity of the previously proposed $K^\pi = 4^+$$\gamma\gamma$-two-phonon state in 168Er at an excitation energy of 2056 keV and of the first excited $K^\pi=0^+$ 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 $4^+_{\gamma\gamma}$state to the $\gamma$-band was remeasured to be \( {\rm B(E}2,4^{+}_{\gamma\gamma}\!\to2^+_\gamma)= (600\pm 130)\;\mbox{e$^{2}$fm$^{4}$}, \)which almost exhausts the harmonic expectation. In addition, the B(E2) values connecting the band head of the lowest lying excited $0^+_{\rm b}$ band to the $2^+_{\rm g}$ and $2^+_\gamma$ states were measured to be B(E2, $2^{+}_{\rm g}\!\to0^+_{\rm b})=(4.4\pm 0.6$) e2fm4 and B(E2, $2^{+}_{\gamma}\!\to0^+_{\rm b})=(30.4\pm 4.6$) e2fm4; the latter is almost a factor of 10 smaller than the B(E2, $2^{+}_{\gamma}\!\to0^+_{\rm g})$ value, which shows that the $0^+_{\rm b}$ band head has no significant contribution of the $K^\pi=0^+$ $\gamma\gamma$-two-phonon state in its wave function.

PACS
21.10.Re Collective levels and giant resonances - 23.20.Ck Lifetimes and transition probabilities - 25.70.Cd Elastic and quasielastic scattering and transfer - 27.70.+q $150\leq A \leq 189$

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