The incomplete fusion reactions ${}^7{\overrightarrow{\mathrm{Li}}}^{158,160}\mathrm{Gd}$ at beam energies of 8 MeV/nucleon have been used to study the first band crossing region in the heavy stable Dy isotopes ${}^{160,162}\mathrm{Dy}.$ The $\gamma$ rays were detected in the GASP spectrometer in coincidence with fast charged particles detected in the ISIS silicon ball. We succeeded to observe the first backbending in ${}^{162}\mathrm{Dy}$ at a crossing frequency of $ħ\omega \approx 350\hspace{0.5em}\mathrm{keV},$ a value much higher than expected from other nuclei in this mass region. Moreover, for the first time in a nucleus with a very large interaction strength, the yrare band in ${}^{160}\mathrm{Dy}$ could be established up to rather high spin $(I=20\mathrm{}ħ)$ allowing for a precise determination of the interaction strength between the ground state and the Stockholm band, $|V_{g-S}|=219\mathrm{}\left(2\right)\mathrm{}\hspace{0.5em}\mathrm{keV}.$ Together with $|V_{g-S}|=14\mathrm{}\left(2\right)\mathrm{}\hspace{0.5em}\mathrm{keV}$ determined for the corresponding interaction in ${}^{162}\mathrm{Dy},$ a full oscillation of the strengths from one node to the next could be observed within an isotopic chain. In addition to the ground state and Stockholm bands, many other known bands in the two nuclei were considerably extended to higher spin and the experimental results are compared to calculations within the projected shell model.

• Received 1 March 2002

DOI:https://doi.org/10.1103/PhysRevC.66.014312