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Excited levels of the strongly-deformed odd-odd nucleus 166Tm, populated by the 165Ho(α,3nγ) reaction, were investigated using standard in-beam γ-ray spectroscopy, including measurements of a few conversion electron lines, and by high-resolution curved-crystal spectroscopy. A level scheme consisting of 178 transitions among 6 well-developed and 4 partial rotational bands is proposed. Level spins and parities were determined and the results were interpreted in the framework of the Nilsson model by comparison with predictions. The Gallagher-Moszkowski splitting for the { π 1 2 + [411] ± ν 5 2 + [642] } configuration was determined to be 245(20) keV. An anomalous signature splitting was observed for the {π 7 2 + [404] + ν 5 2 + [642]}K π = 6 + configuration.

Excited states of 166 Tm were investigated by means of the 165 Ho(α, 3n) reaction. Two rotational bands were identified up to tentative spins of 20 − and 18 + . Their electromagnetic.properties were studied and interpreted in the framework of the cranking shell model (CSM) and of the particle-rotor model (PRM). Both the revised Donau and Frauendorf formula (CSM) and the PRM calculations reproduce the experimental results rather well for spins between 10 and 14, whereas they fail at low and high angular momenta. The two models predict different I -dependences for the B (M1) values in the angular momentum region of I j p + j n . The existence and interpretation of the signature inversion of the yrast band is discussed using three different models. The results show that the occurrence of signature inversion does not necessarily mean the presence of trixial nuclear shape.

The nuclear levels in 174 Lu were investigated by means of 176 Yb(p, 3nγ) reaction spectroscopy. Standard germanium detector techniques as well as an on-line curved crystal spectrometer were used. Six well-developed rotational bands are observed. These results confirm and extend the scheme previously obtained by direct reactions. The presented data document a study on the anomalous g -factors of the 142 d isomeric band.