Isomer Ratios in Photonuclear Reactions With Multiple Neutron Emission

Abstract

The aim of this work is studying of gamma-quanta energy dependence of isomeric ratios in A(γ,xn)m,g(A − xn) reactions in energy range 35...100MeV , i.e. beyond Great Dipole Resonance (GDR) region. Experimental data were taken from international database EXFOR for a wide range of nuclear mases (55 < A < 181). Theoretical values of isomeric ratios were obtained using TALYS-1.8 code. Several models of level densities with both enabled and disabled pre-equilibrium mechanism were considered in our simulations. Obtained results let us to make conclusions about different mechanisms of photonuclear reactions on certain nuclei, energy dependence of their relative contribution.

Isomeric pair 95 m,g Nb in the photonuclear reactions on natMo at the bremsstrahlung end-point energy of 38–93 MeV

“…As a result, to find the experimental values of the IR, it is necessary to solve the system of equations describing the radioactive decay of the metastable state and decay with accumulation for the ground state. The solution of such a system of equations is described in several works [4,44,45], with different analytical representations.…”

Photoneutron reactions on 93Nb at Emax=33–93 MeV

“…Summarizing the analysis of the known experimental data on the photodisintegration of 93 Nb in the region of -quanta energies above 30 MeV, it should be noted that they are extremely discrete and local. It will be fair to say that a similar situation has developed for other nuclei, despite the many years of efforts made by experimenters to solve this problem [32,33].…”

“…The errors in the data obtained were mainly determined by the errors given for the values of the half-life and absolute intensity of lines for the 89 Nb nucleus in the isomeric and ground states (see Table 1). More detailed calculations of isomeric ratios for this reaction were carried out by us earlier [32] using the TALYS1.8 code. In our simulations, we used several level density models incorporated in TALYS1.8, but we failed to satisfactorily describe the behavior of the energy dependence of isomeric ratios obtained in the experiments of Naik et al [22].…”

Study the Isomeric Ratios in Photonuclear Experiments on the Lue-40 Linac RDC “Accelerator” NSC Kipt

“…The isomeric ratios IR for most photonuclear reactions change rapidly as the bremsstrahlung end-point energies increase from the reaction threshold up to the end of the GDR region. After 30 MeV the IR increases slowly or saturates in all energy ranges, as shown in the reviews [23,24]. The fast-increasing isomeric ratios can be explained by a compound nuclear reaction mechanism in which the increased momentum was transferred to the compound nuclei.…”