The yield ratio of the high-spin state of 122mSb (8−) and the low-spin state of 122gSb (2−) formed via the 123Sb(γ,n)122m,g Sb reaction has been measured as a function of the bremsstrahlung end-point energy in the range of 40-MeV to 60-MeV. Use was made of the activation technique in combination with high-resolution γ-ray spectrometry. The isomeric yield ratios for the 123Sb(γ,n)122m,g Sb reaction measured at 40-, 45-, 50-, 55-, and 60-MeV bremsstrahlung are ± , ± , ± , ± , and ± . According to our | Communications in Physics, Vol. 22, No. 1 (2012), pp. 75-81 MEASUREMENT OF THE YIELD RATIO OF THE 122m,g Sb ISOMERIC PAIR ABOVE THE GIANT RESONANCE PHAM DUC KHUE, KIM TIEN THANH, AND NGUYEN VAN DO Institute of Physics, VAST Abstract. The yield ratio of the high-spin state of 122m Sb (8− ) and the low-spin state of 122g Sb (2− ) formed via the 123 Sb(γ,n)122m,g Sb reaction has been measured as a function of the bremsstrahlung end-point energy in the range of 40-MeV to 60-MeV. Use was made of the activation technique in combination with high-resolution γ-ray spectrometry. The isomeric yield ratios for the 123 Sb(γ,n)122m,g Sb reaction measured at 40-, 45-, 50-, 55-, and 60-MeV bremsstrahlung are ± , ± , ± , ± , and ± . According to our knowledge, the present results are the first measurement. I. INTRODUCTION The isomeric ratio is defined as the ratio of the cross-section for the production of an isomeric state over that of unstable ground state (σ m /σ g ). Studies of isomeric ratios are of great importance in both fundamental nuclear physics research and applications [1-6]. So far, the isomeric ratios are mainly measured on nuclear reactions induced by neutrons [7-12], charged particles [13-16], and bremsstrahlung photons [3,5,17,18]. The measurement with gamma quanta as projectiles has some essential advantages in studying nuclear structure and nuclear reaction mechanism. In the present work we have chosen the 123 Sb(γ,n)122m,g Sb photonuclear reactionfor studies. From literature we have found some experimental data for the 123 Sb(γ,n)122m,g Sb reaction, but all of them were measured at low-energies, from threshold up to 22-MeV [17,18]. For those reactions, the reaction mechanisms are well understood at low-energy, but very little is known in detail about the reaction mechanisms that proceed at higher energies. In this work we extend our measurements to higher incident bremsstrahlung energies, from 40-MeV to
