Study of Isomeric States Formation by Nuclear Reaction of Light Particles on Some Nuclei

Abstract

The thermal cross section and resonance integral for 79Br (n,γ)80m+gBr was identified as σm,gBr,0 = 10.05±0.3 b and Im,gBr,0=89.38±2.68 b and for 81Br (n,γ)82m+gBr was identified as σm,gBr,0 = 2.12±0.06b and Im,gBr,0= 46.03±1.38b. Model calculations were done using EMPIRE code to simulate isomeric ratio and compared with the experimental results. Steady neutron field could be retained with isotopic neutron source with moderation setup and geometry of suitable homogeneity and isotropy. In the present work the effects of isomeric state formation on the measurement of thermal neutron cross section and its associated resonance integral on neutrons reaction are discussed. The isomeric thermal neutron cross section and isomeric resonance integral of 109Ag (n, γ) 110mAg, 133Cs (n, γ) 134mCs and 134gCs, and 136Ba (n, γ) 137mBa, 68Zn (n,γ)69mZn, 79Br(n,γ)80m+gBr and 81Br(n,γ)82m+gBr reactions were investigated together with 115In (n, γ) 116mIn monitor reaction. These residual nuclei have broad half-life time scale suitable for our investigation; (isomeric states having different half-life time from 2.5 min to 2 year). Moderated neutrons from steady Am-Be sources were used for neutron activation. Field was monitored and mapped using gold and indium activation. The k0-factor was measured for some residual nuclei, hence the k0-factor for 137mBa was measured for the first time. The isomeric thermal neutron cross section and resonance integral for 115In (n, γ) 116mIn were evaluated to be 162.6 b and 2585 b. These data were used to measure the k0-factors; and compared to reported values to confirm the present procedure. The thermal neutron cross section and resonance integral for 133Cs (n, γ) 134mCs were found to be 2.64±0.11 b and 42±1.7 b, respectively; while those of the 109Ag (n, γ) 110mAg reaction were 4.09±0.35 b and 68±6 b. Thermal neutron cross section for 136Ba (n, γ) 137mBa was identified as 0.032±0.003 b, while the resonance integral could not be evaluated as a result of interfering reactions.