Particle-$\gamma$ coincidence experiments were performed at the Oslo Cyclotron Laboratory with the ${}^{181}\mathrm{Ta}(d,X)$ and ${}^{181}\mathrm{Ta}({}^3\mathrm{He},X)$ reactions to measure the nuclear level densities (NLDs) and $\gamma$-ray strength functions ($\gamma \mathrm{SFs}$) of ${}^{180,181,182}\mathrm{Ta}$ using the Oslo method. The back-shifted Fermi-gas, constant temperature plus Fermi gas, and Hartree-Fock-Bogoliubov plus combinatorial models were used for the absolute normalizations of the experimental NLDs at the neutron separation energies. The NLDs and $\gamma \mathrm{SFs}$ are used to calculate the corresponding ${}^{181}\mathrm{Ta}(n,\gamma )$ cross sections and these are compared to results from other techniques. The energy region of the scissors resonance strength is investigated and from the data and comparison to prior work it is concluded that the scissors strength splits into two distinct parts. This splitting may allow for the determination of triaxiality and a $\gamma$ deformation of $14.9^{\circ }\pm 1.8^{\circ }$ was determined for ${}^{181}\mathrm{Ta}$.

• Received 3 December 2018
• Revised 25 February 2019

DOI:https://doi.org/10.1103/PhysRevC.99.054330