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

TL;DR

This study measured the isomeric ratio and cross-sections of the $^{181}$Ta(n) reaction at energies up to 95 MeV, comparing experimental results with theoretical models to evaluate their accuracy.

Contribution

It provides new experimental data on the isomeric ratio and cross-sections for the $^{181}$Ta(n) reaction and assesses the performance of different level density models in theoretical calculations.

Findings

Experimental isomeric ratios agree with literature but differ from theory.

Best theoretical agreement with the LD 5 level density model.

Experimental cross-sections show energy dependence deviations from models.

Abstract

The photoneutron reaction $^{181}\rm{Ta}(\gamma,3n)^{178m,g}\rm{Ta}$ was investigated with the beam from the NSC KIPT electron linear accelerator LUE-40. The measurements were performed using the residual $\gamma$-activity method. The bremsstrahlung flux-averaged cross-sections $\langle{\sigma(E_{\rm{\gamma max}})}\rangle$, $\langle{\sigma(E_{\rm{\gamma max}})}\rangle_{\rm{m}}$, $\langle{\sigma(E_{\rm{\gamma max}})}\rangle_{\rm{g}}$ and the isomeric ratio of the reaction products $d(E_{\rm{\gamma max}})$ 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 $d(E_{\rm{\gamma max}})$ 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.