Measurement of isomeric yield ratios of 86m,gY, 87m,gY, and 89m,gZr in the photonuclear reactions of 89Y and natZr at the end-point bremsstrahlung energies of 45 and 55Â MeV

The isomeric yield ratios of 86m,gY, 87m,gY, and 89m,gZr produced in the reactions of 89Y and natZr with end-point bremsstrahlung energies of 45 and 55 MeV have been determined by activation and off-line γ-ray spectrometric technique using the 100 MeV electron linac at Pohang Accelerator Laboratory (PAL), Korea. The present data along with literature data show that the isomeric yield ratios of 86m,gY and 87m,gY in the 89Y(γ,xn) and natZr(γ,x) reactions and those of 89m,gZr in the natZr(γ,x) reaction increase with the end-point bremsstrahlung energy, which indicates the effect of excitation energy. However, the increase trend of the isomeric yield ratios of 87m,gY in the 89Y(γ,xn) reaction and 89m,gZr in the natZr(γ,x) reaction are very fast from the threshold value to 30 MeV due to the giant dipole resonance effect. After certain point of excitation energy, the isomeric yield ratios increase slowly with the end-point bremsstrahlung energy due to the partition of energy in different reaction channels. It was also observed that in both the reactions, the isomeric yield ratios of 87m,gY are always higher than those of 86m,gY. This is because of more number of particle emission and thus the disposition of more excitation energy needed for the formation of 86m,gY compared to 87m,gY.