Excitation of isomeric states in reactions (γ, n) and (γ, 2n) on 197Au nuclei

The measurement and interpretation of isomer rations have provided detailed information about the energy level structure of nuclear systems and the angular momentum and reaction mechanism effects involved in the production of isomeric states in nuclei. In the present work the results of the experimental study of the photoexcitation of isomeric states 197mAu(Jπ=11/2-), 196mAu(Jπ=12-) and 195mAu(Jπ=11/2-) in reactions(γ, γ), (γ, n) and (γ, 2n) on nuclei in the range 10-25 MeV are presented. The isomeric yield ratios were measured by the induced radioactivity method. The samples of 99.9% pure metallic gold have been irradiated in the bremsstrahlung beam of the betatron SB-50 of Institute of Applied Physics of National University of Uzbekistan. A device for the intra-chamer bremsstrahlung irradiation of samples in a betatron, combined with a K5-2A pneumotransport system was used in order to increase the density of the bremsstrahlung flux was used. The induced activities were examined by detecting and analyzing γ-rays with help of a 63 cm3 Ge(Li) semiconductor spectrometer equipped with a 4096 channel pulse height analyzer. The counting system had a resolution of ∼3.5 keV for the 1332 keV γ-line of 60Co. Isomeric ratios for 197Au(γ, n) 196m,gAu reaction yields are measured in the 12-30 MeV energy range with 1 MeV energy step. The obtained Eγwax dependence of the isomeric ratio yields for the (γ, n) reaction, , looks like a saturation curve. In the saturation region = (5.6±0.4)10-4 .The results are in good agrement with the data of ref. For (γ, 2n)m reaction cross sections are obtained at first. The cross section isomeric ratios of Em=17 MeV are estimated. Experimental isomeric ratios are compared with calculations by a statistical model of nuclei.