Investigation of the 11/2^-isomeric state excitation of the ¹³⁷Ba nucleus in the (γ, γ')^m reaction

Abstract

ДОСЛІДЖЕННЯ ЗБУДЖЕННЯ ІЗОМЕРНОГО СТАНУ 11/2 − ЯДРА 137 Ва В РЕАКЦІЇ (γ, γ ′ ) m Виконане теоретичне та експериментальне дослідження перерізу збудження ізомерного стану 11/2 − ядра 137 Ва в реакції (γ, γ ′ ) m . Експериментальне дослідження проводилося на гальмівному пучку мікротрону М-30 в області енергій 4-17 МеВ. Ключові слова: атомне ядро, ядерні реакції, переріз, гігантський дипольний резонанс, гальмівний гаммаспектр, ізомерне відношення. INVESTIGATION OF THE 11/2 − ISOMERIC STATE EXCITATION OF THE 137 Ba NUCLEUS IN THE (γ, γ ′ ) m REACTION Purpose. To determine the (γ, γ ′ ) m reaction cross section dependence on the gamma-quanta energy for the 137 Ba nucleus. Methods.Activation analysis used for the measurement of the reaction output channels. Results.This paper presents measurement results for the experimental determination of the 137 Ba(γ, γ ′ ) 137m Ba reaction cross section in the region E γmax = 5−18 MeV for the maximum energies of the bremsstrahlung gamma-spectra. The work was performed on a beam of M-30 microtron electron accelerator Bremsstrahlung gamma rays. The energy dispersion of the accelerated electrons was ± (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) keV. The induction of the magnetic field of the accelerator and the corresponding energy of the accelerated electrons were determined by the method of nuclear magnetic resonance, and the measurement error did not exceed ±0.1%. The experimental yield curve of the reaction 137 Ba(γ, γ ′ ) 137m Ba was measured in 0.5 MeV increments and was used to calculate the cross section σ m (E) of the reaction (γ, γ ′ ) m . Calculations of σ m (E) were performed by the Penfold-Leiss method. The obtained experimental results were compared with theoretical calculations performed using the TALYS-1.9 software. Conclusion. In the obtained cross-sections a peak can be observed with a maximum of 0.8 mb at 7.0 MeV, and a smaller peak with a maximum at 15 MeV. The observation, that the theoretical cross section closely follows the experimental data points to the domination of the statistical mechanism in the (γ, γ ′ ) m reaction.