Measurement of isomeric yield ratios of 86m,g Y, 87m,g Y, and 89m,g Zr in the photonuclear reactions of 89 Y and nat Zr at the end-point bremsstrahlung energies of 45 and 55 MeV

Tatari, Mansoureh; Kim, Gui Nyun; Naik, H.; Kim, Kawngsoo; Yang, Sung Chul; Zaman, Muhammad; Shin, Seung Gu; Kye, Yong-Uk; Cho, Moo‐Hyun

doi:10.1016/j.nimb.2014.12.019

Cited by 6 publications

(1 citation statement)

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“…The spin distribution of the nuclear levels can be studied experimentally by investigating the rotational bands of the nuclei [1] or by studying the isomeric cross-section ratios. The dependence of the isomeric ratio on the excitation energy of the product nucleus as well as on the spins of the two states concerned has been demonstrated by considering data for (n, γ), (n, 2n), (n, p), (n, α) and (γ, n) reactions [2][3][4][5][6]. In charged particle induced reactions, a comparison of measured isomeric cross-section ratios with values obtained from nuclear model calculations also sheds light on the spin distribution of levels involved [7][8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%

Mass number and excitation energy dependence of the Θ /Θ parameter of the spin cut-off factor in the formation of an isomeric pair

Sudár

Qaim

2018

Nuclear Physics A

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The Θ ef f /Θ rig parameter of the spin distribution of the level density of an excited nucleus was determined for 61 nuclei covering the mass range of 44 to 200. The experimental isomeric crosssection ratios for 25 isomeric pairs were compared with the model calculation to find the best fit to the experimental data. An isomeric cross-section ratio may be affected by more nuclei depending on the reaction. The model calculations were carried out with the TALYS code using the backshifted Fermi gas model for the level density. The reduced χ 2 values were calculated to describe the deviation of the experimental data from the model calculation as a function of the η = Θ ef f /Θ rig parameter. The minimum of the reduced χ 2 curve defined the best probable Θ ef f /Θ rig parameter. An η d was introduced calculating the Θ ef f /Θ rig value from the low energy discrete levels of the nucleus. The η/η d values seem to be independent of the mass number, their average value near to one, but showing slight dependence on the odd-even characteristic of the proton and neutron number. The η/η d values also seem to be independent of the average excitation energy in the continuum, indicating that η is independent of the excitation energy. The mass number and (N-Z) dependence of the η values were studied. The η values for the nuclei with odd mass number show a characteristic exponential decrease as a function of the mass number or (N-Z). The η values for the odd-odd type of nuclei appear to be constant, near one, up to the mass number 110 or (N-Z) of 13. Above these values, the η values show characteristic exponential decrease like nuclei with the odd mass number. The η values for even-even type nuclei decrease exponentially up to A equal to 142 or (N-Z) equal to 20. The values are lower than those for the nearby odd-odd type nuclei.The η values increase for nuclei with A between 142 and 156 and (N-Z) between 20 and 28, and they finally reach the value of odd-odd type systematics. This behavior indicates some individual properties of the 156 Gd. The odd-even effect of Θ ef f /Θ rig may change the calculated activation cross section significantly in some energy regions.

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