Investigation of Excitation of $${K}$$ Isomers $${}^{{179m2}}$$Hf and $${}^{{180m}}$$Hf in ($${\gamma,\gamma^{\prime}}$$) Reactions

Abstract

The weighted-average cross sections for $${}^{179m2}$$ Hf and $${}^{180m}$$ Hf population in ( $$\gamma,\gamma^{\prime}$$ ) reactions induced by gamma rays of bremsstrahlung spectrum with endpoint energies of 17.5, 37, and 55 MeV were measured for the first time. A second maximum in the excitation function for the $$K$$ forbidden isomers of $${}^{179}$$ Hf and $${}^{180}$$ Hf was found in the energy range between 20 and 35 MeV. A respective simulation was performed within the model of pre-equilibrium processes and within the statistical model by employing the TALYS-1.9 and EMPIRE-3.2 codes. It is shown that the integrated cross sections for ( $$\gamma,\gamma^{\prime}$$ ) reactions in the energy range between 20 and 55 MeV are described in the statistical limit of the compound-nucleus volume (TALYS-1.9 code).