⁹⁵Tc and⁹⁶Tc production by (γ, xn) reactions

The⁹⁹Tc (γ, 3n)⁹⁶Tc and⁹⁹Tc (γ, 4n)⁹⁵Tc reactions were studied by irradiation of target⁹⁹Tc with bremsstrahlung from the linear electron accelerator of Tohoku University, up to 50 MeV γ-energy. The resulting⁹⁶Tc (4.3 d) and⁹⁵Tc (20 h) activities were determined by γ-spectrometry. The γ-flux was monitored by the⁹⁹Tc (γ, γ′)^99mTc reaction. Metallic copper and gold foils were used as additional flux monitors in front of and behind the samples. Their measured radioactivity was utilized for normalizing bremsstrahlung flux calculations, in order to determine reaction cross sections. Cross sections were also determined theoretically, performing calculations in the framework of a neutron cascade evaporation model. Above the (γ, 3n) and (γ, 4n) threshold energies the neutron emission channel was supposed to be the only open channel for deexcitation following photoabsorption. The preeguilibrium contribution was considered negligible. The experimental results obtained for the integrated cross section at 30 and 50 MeV fit reasonably well the calculated curves.