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Isomeric Ratio of the $^{181}\rm{Ta}(γ,3n)^{178m,g}\rm{Ta}$ Reaction Products at Energy $E_{\rm{γmax}}$ up to 95 MeV

The photoneutron reaction $^{181}\rm{Ta}(γ,3n)^{178m,g}\rm{Ta}$ was investigated with the beam from the NSC KIPT electron linear accelerator LUE-40. The measurements were performed using the residual $γ$-activity method. The bremsstrahlung flux-averaged cross-sections $\langle{σ(E_{\rm{γmax}})}\rangle$, $\langle{σ(E_{\rm{γmax}})}\rangle_{\rm{m}}$, $\langle{σ(E_{\rm{γmax}})}\rangle_{\rm{g}}$ and the isomeric ratio of the reaction products $d(E_{\rm{γmax}})$ have been measured. Theoretical values of averaged cross-sections and isomeric ratio were calculated using partial cross-sections from the TALYS1.95 code for different level density models $LD$ 1-6. The obtained experimental $d(E_{\rm{γmax}})$ agree with the literature data, but differ from the theoretical values in absolute magnitude and the behavior of the energy dependence. A comparison of the found averaged cross-sections with the calculated ones showed the best agreement for the case of the $LD$ 5 model.