Pseudo-spin band in the odd-odd nucleus 172Lu

High-spin states in the odd-odd nucleus 172Lu have been populated in a 170Er(7Li, 5n) reaction and the emitted \(\gamma\)-radiation was detected with the GASP array. Two sequences of a new identical band have been observed with the transition energies in the favoured and unfavoured sequences being identical within \(\approx 3\) keV at low spins and \(\approx 1\) keV at high spins over the whole observed spin range. Aninterpretation as a pseudo-spin singlet band of \(\pi 1/2^- [541] \otimes \nu 1/2^- [\widetilde{420}]\) configuration is proposed. It represents the best example of a pseudo-spin singlet band in normal deformed nuclei known until now.