Investigation of isomer ratio in (γ, 2n) phoionnuclear reactions on 89Y, 113In and 197Au nuclei

In the work the results of the investigation of isomeric yields ratios Ym/Yg and isomeric cross section ratios σm/σg of reactions 89Y(γ, 2n)87m,gY, 113In(γ, 2n)111m,gIn and isomeric cross section ratios σm/σg of the reactions 197Au(γ, 2n)195mAu by the induced radioactivity method in the energy range of 15-35 MeV with energy step of 1 MeV are presented. A device for the intra-chamber Bremsstrahlung irradiation of samples in betatron, combined with a K5-2A pneumatic transport system was used in order to increase the density of the Bremsstrahlung flux. The device is mounted at a distance of 14 cm from the tungsten target of a high-current SB-50 betatron which allows the samples to be transferred in plastic containers without a risk of overheating. The induced activities were examined by detecting and analyzing γ-rays with help of 63 cm3 Ge(Li) semiconductor spectrometer equipped with a 4095 channel pulse height analyzer. The counting system had a resolution of 3.5 keV for the 1332 keV γ-line of 60Co. The isometric ratios were calculated according to the equation of Vanska and Rieppo. The experimental results are compared with the calculations made in statistical Fermi-gas theory. The experimental results are in agreement with the calculated ratios for values of spin cut-off parameter σ between 2 and 3