Search

The low-lying dipole strength of the open-shell nucleus ${}^{94}$Mo was studied via the nuclear resonance fluorescence technique up to 8.7 MeV excitation energy at the bremsstrahlung facility at the Superconducting Darmstadt Electron Linear Accelerator (S-DALINAC), and with Compton backscattered photons at the High Intensity $\ensuremath{\gamma}$-ray Source (HI$\ensuremath{\gamma}$S) facility. In total, 83 excited states were identified. Exploiting polarized quasi-monoenergetic photons at HI$\ensuremath{\gamma}$S, parity quantum numbers were assigned to 41 states excited by dipole transitions. The electric dipole-strength distribution was determined up to 8.7 MeV and compared to microscopic calculations within the quasiparticle phonon model. Calculations and experimental data are in good agreement for the fragmentation, as well as for the integrated strength. The average decay pattern of the excited states was investigated exploiting the HI$\ensuremath{\gamma}$S measurements at five energy settings. Mean branching ratios to the ground state and first excited ${2}_{1}^{+}$ state were extracted from the measurements with quasi-monoenergetic photons and compared to $\ensuremath{\gamma}$-cascade simulations within the statistical model. The experimentally deduced mean branching ratios exhibit a resonance-like maximum at 6.4 MeV which cannot be reproduced within the statistical model. This indicates a nonstatistical structure in the energy range between 5.5 and 7.5 MeV.