Bezshyyko O. Investigation of photonuclear reactions for nuclei 238U, 237Np, 232Th, 123Sb, 121Sb, 118Sn with using isomer ratio method

The isomer ratios have been measured and angular momenta have been obtained for the fragments 84Br, 129Sb, 130Sb, 131Te, 132Sb, 133Te, 134I, 135Xe from 238U photofission and for fragments 134I, 135Xe from 237Np photofission by the bremsstrahlung gamma-quanta having maximum energy of the spectrum Emax=16 MeV. The new experimental data on the isomer ratios for reactions 118Sn(g,p)117m,gIn, 121Sb(g,n)120m,gSb, 121Sb(g,n)120m,gSb have been obtained using bremsstrahlung spectrum with maximum energy 15 and/or 16 MeV. The method of isomer ratios has been developed for study the angular momenta of highly excited nuclear states. Code Empire II was modified and used for calculations of isomer ratios of the products of photonuclear reactions. The model of Huizenga and Vandenbosh for calculation of isomer ratios was tested with use of the experimental data base on levels and transition probabilities of the RIPL-2 library. It is shown that for major part of nuclei the approximation of Huizenga and Vandenbosh onthe last transition is either not applicable or could be applied with considerable restrictions.