High-Spin States in Odd-Odd ¹⁶⁸Lu

Abstract

We observed four rotational bands in ¹⁶⁸Lu using the ¹⁵⁹Tb(¹³C,4nγ)¹⁶⁸Lu reaction at 58.5 MeV and 62 MeV and populated high spin states up to 27 \hbar. On the basis of the X-γ gating procedure and excitation function measurements done at beam energies of 50, 55, 58.5, 60, 62 and 64 MeV, we could identify the γ-ray transitions belonging to ¹⁶⁸Lu. The configurations of two strongly populated rotational bands (bands A and B) were based on our previous study and were examined by using the additivity relation for alignments. The configurations of two newly found rotational bands (bands C and D) were also assigned by the additivity relation. These identified configurations were confirmed by the Drissi's recipe and energy systematics of neighboring odd-odd nuclei. The configuration of bands A was assigned as K^π = 6⁺ [π7/2⁺[404] + ν5/2⁺[642]]. The configurations of the previous reported band B and two new bands C and D are likely to be 3^-[π1/2^-[541]+ν5/2⁺[642]], 7^-[π9/2^-[514]+ν5/2⁺[642]] and 5⁺[π5/2⁺[402]+ν5/2⁺[642]], respectively. We observed band crossing for three bands A, C and D, but not for band B. The extracted band crossing frequencies were consistent with the neutron BC crossing observed in neighboring odd-odd nuclei as well as odd-N and even-Z nuclei in this mass region. This was attributed to the occupied ν5/2⁺[642] Nilsson configuration arising from the neutron ν i_13/2 orbital. Energy systematics of bands built on π g_7/2 \otimes ν i_13/2 and π h_11/2 \otimes ν i_13/2 in neighboring odd-odd nuclei were also studied in comparison with bands A and C in ¹⁶⁸Lu.