Isomeric yield ratios and mean angular momenta of photofission fragments of 235U, 237Np and 239Pu

Abstract

Измерены изомерные отношения выходов фрагментов фотоделения ядер 235 U, 237 Np и 239 Pu тормозными γквантами с граничной энергией 18 МэВ. Получены новые данные для выходов изомерных пар ядер 84 Br, 90 Rb, 131 Te, 132 Sb, 132 I, 133 Te, 134 I, 135 Xe. Изомерные отношения определены с вычетом вклада заселенностей состояний исследуемых фрагментов от β-распада соответствующих изобарных ядер. Определены средние угловые моменты фрагментов деления в рамках обобщенной статистической модели Хьюзенга-Ванденбоша с использованием кода EMPIRE 3.2. Ключевые слова: фотоделение, метод изомерных отношений, средние угловые моменты продуктов деления. ISOMERIC YIELD RATIOS AND MEAN ANGULAR MOMENTA OF PHOTOFISSION FRAGMENTS OF 235 U, 237 Np AND 239 Pu Isomeric yield ratios for the fragments of photofission 235 U, 237 Np and 239 Pu by bremsstrahlung with end-point energy of 18 MeV are measured. New data for isomeric yield ratios of the fragments 84 Se, 90 Br, 131 Te, 132 Sb, 132 I, 133 Te, 134 I, 135 Xe are determined. The contributions to the isomeric yield ratios from β-decay of the nuclei of parent isobaric chain were removed. Mean angular momenta of studied nuclei are estimated within the framework of an extended Huizenga-Vandenbosh statistical model with using EMPIRE 3.2 code.

Isomer Ratios and Mean Angular Momenta of Primary 97Nb Fragments at 235U and 238U Photofission

“…When calculating the isomeric ratios, we used a generalization of the Huizenga-Vandenbosh statistical model, which was proposed in Refs. [9,10]. Furthermore, we took into account the population of the ground ( ) and metastable ( ) states of the researched nucleus ( , ) with charge emerging owing to the decay of isotopes ( = + , ) with a larger number of neutrons ( ≤ ).…”

“…Δ = 2¯) and involves almost all excited states that can populate the ground and isomeric states of the researched nucleus (see As was done in Refs. [9,10], the parameter in formulas (3) and (4) was calculated in the framework of the Fermi model for the gas of spherical nuclei. The parameters and were found by fitting the theoretical values of isomeric ratio (2) to experimental data.…”

“…This work continues a cycle of researches dealing with the isomeric ratios and the mean angular momenta of photofission fragments of actinide nuclei (see Refs. [7][8][9][10][11] and references therein). Its aim consists in the determination of the isomeric yield ratios for the primary 97 Nb nucleus fragment and the determination of its mean angular momentum in the photofission reactions of 238 U and 235 U nuclei with the use of the bremsstrahlung with various end-point energies.…”

Photofission of 238U with bremsstrahlung in wide interval of values of the boundary energy

“…Для теоретичного розрахунку ІВ використовувалося розроблена в [7,13] узагальнена статистична модель Хьюзенги -Ванденбоша [14,15]. Враховувалась заселеність основного (g) та метастабільного (m) станів досліджуваного ядра (A f , Z f ) вiд розпаду ізотопів із масовим числом A i = A f + i з більшою кількістю нейтронів i ≤ i m .…”