Photonuclear reactions on molybdenum isotopes
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CLEI Theory
Photonuclear Reactions on Molybdenum Isotopes B. S. Ishkhanov1), 2) , I. M. Kapitonov1), A. A. Kuznetsov2)* , V. N. Orlin2) , and Han Dong Yoon1) Received March 11, 2014
Abstract—The results of experimentally and theoretically studying the photodisintegration of molybdenum isotopes are presented. The yields of various photonucleon reactions on stable molybdenum isotopes were determined by the gamma-activation method. Use was made of bremsstrahlung photons from an electron accelerator that were characterized by the endpoint energies of 19.5, 29.1, and 67.7 MeV. Reactions involving the emission of up to three nucleons from the target nucleus were observed. The experimental results in question were compared with theoretical predictions based on the combined photonucleonreaction model and obtained for 15 molybdenum isotopes. The relations between basic photonucleon reactions on the molybdenum isotopes considered in our present study were explained. DOI: 10.1134/S106377881410007X
1. INTRODUCTION At photon energies in excess of the nucleonseparation energy, various collective oscillations of nucleons are vigorously excited in nuclei. The giant dipole resonance (GDR) is a dominant collectiveoscillation type in the photon-energy region extending from 10 to 35 MeV. Its investigation contributes greatly to obtaining deeper insight into the nature of high-energy nuclear excitations [1–4]. At energies around 10 to 20 MeV and below, giant dipole resonances decay predominantly through the emission of one neutron or one proton from the nucleus being considered. These are (γ, n) and (γ, p) reactions. Above the GDR maximum, photonuclear reactions involving the emission of two, three, or more nucleons from the excited nucleus begin to play a significant role. Experimental data on these reactions are substantially scantier than data on single-nucleon reactions. At the same time, the former are precisely the reactions that determine the character of relaxation of nuclear excitations within the high-energy section of the giant dipole resonance, where the role of the quadrupole and quasideuteron excitation of nuclei becomes substantial [5, 6]. The branching ratios of various photonucleon reactions on molybdenum isotopes are another aspect of photonucleon reactions that have not yet received adequate study. By tracing the change in these ratios upon going over from one isotope to another, one 1)
Moscow State University, Moscow, 119991 Russia. Skobeltsyn Institute of Nuclear Physics, Moscow State University, Moscow, 119991 Russia. * E-mail: [email protected]
2)
can obtain new information about the mechanisms of decay of high-energy nuclear states. Mediummass and heavy nuclei, which frequently have long chains of stable isotopes, are especially convenient for studying this aspect of photonuclear disintegration. The objective of the present study is to obtain new information about basic photonuclear reactions on molybdenum isotopes over a broad region of photon energies. We have performed both experimental and theoret
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