Formation of high-spin neodymium and mercury isomers in neutron and charged particle induced nuclear reactionsS. Sudár1, 2, K. Hilgers2, M. Al-Abyad2, 3 and S.M. Qaim2
1 Institute of Experimental Physics, University of Debrecen, Bem tér 18/a, 4026 Debrecen, Hungary
2 Institut für Nuklearchemie, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
3 Cyclotron Facility, Nuclear Research Centre, Atomic Energy Authority, Cairo 13759, Egypt
Published online: 21 May 2008
The isomeric pairs 195m,gHg, 197m,gHg, 139m,gNd and 141m,gNd constitute interesting cases since the ground state has a low spin and the isomeric state a relatively high spin. Their formation was studied in several reactions induced by n, p, 3He, and α-particles. The four projectiles were produced at the Jülich variable-energy compact cyclotron (CV 28); for neutron production the 2H(d,n)3He reaction was used. The cross sections were measured by the activation technique. From the available experimental data, isomeric cross-section ratios were determined. Nuclear model calculations using the code STAPRE, which employs the Hauser-Feshbach and exciton model formalisms, were undertaken to describe the formation of both the isomeric and the ground states of the products. The calculations were compared with the results of the EMPIRE-II code. The total reaction cross section of a particular channel is reproduced fairly well by the model calculations, with STAPRE giving slightly better results. Regarding the isomeric cross sections, the agreement between the experiment and theory is only in approximate terms. A description of the isomeric cross-section ratio by the model was possible only with a very low value of η (η = Θeff/Θrig) for the mercury isotopes, while slightly larger η values were needed for neodymium isotopes. An exponential mass dependence of η is proposed.
© CEA 2008