Study of photonuclear reactions with the alpha particles' emission on zirconium, niobium, and molybdenum

Photonuclear reactions with the emission of protons and alpha particles have been little studied experimentally since their cross-sections are much smaller than those of the (gamma, n) channel due to the Coulomb barrier. However, the study of such reactions is of great applied interest to producing medical isotopes. Besides, experimental data on photonuclear reactions with the emission of charged particles for nuclei with Z = 40, 41, 42 open up great opportunities for learning the role of magic numbers. In the presented article, we obtained the weighted average yields of (gamma, an)-reactions for natural zirconium, niobium, and molybdenum at bremsstrahlung gamma-quanta of 20 MeV boundary energy for the first time. A significant effect of a closed N = 50 shell was established on the reaction yield with the emission of alpha particles. Our research shows that the semi-direct mechanism for (gamma, an) reactions dominates in the energy range below the Coulomb barrier. As a result, we can note the prospects of applying (gamma, an)-reaction on Mo-94 to produce the Zr-89 promise medical radionuclide isotope using electron accelerators.