The strength distribution of low-lying dipole excitations in the heavy odd-mass nucleus ${}^{181}\mathrm{Ta}$ was studied in nuclear resonance fluorescence experiments performed at the bremsstrahlung beam of the Stuttgart 4.3 MV Dynamitron accelerator. To increase the detection sensitivity in the whole range of excitation energies between 1.8 and 4 MeV two measurements were carried out at different bremsstrahlung end-point energies of 2.7 and 4.1 MeV using two large-volume HPGe detectors of a relative efficiency of 100%. Detailed information on excitation energies, decay widths, transition probabilities, and branching ratios of 37 new low-lying states in the energy range 1.8–3.5 MeV have been obtained. The observed dipole strength is rather fragmented, apart from a strong excitation at 2.297 MeV. The total strength in the investigated range of excitation energies (1.8–4 MeV) is reduced by a factor of $\approx 3.5$ as compared to the neighboring even-even nucleus ${}^{180}\mathrm{Hf}$.

• Received 10 March 1998

DOI:https://doi.org/10.1103/PhysRevC.58.765