Bulg. J. Phys. vol.44 no.4 (2017), pp. 489-497

Neutron Transfer Reactions for Deformed Nuclei Using Sturmian Basis States

V.G. Gueorguiev1,2, J.E. Escher3
1Ronin Institute, NJ, USA
2Institute for Advanced Physical Studies, Sofia, Bulgaria
3Lawrence Livermore National Laboratory, Livermore, California, USA
Abstract. We study the spin-parity distribution P(Jπ,E) of 156Gd excited states above the neutron separation energy Sn = 8.536 MeV [1] that are expected to be populated via the 1-step neutron pickup reaction 157Gd(3He,4He)156Gd. In analogy with the rotor plus particle model [2], we view excited states in 156Gd as rotational excitations built on intrinsic states consisting of a neutron hole in the 157Gd core; that is, a neutron removal from a deformed Woods-Saxon type single-particle state [3] in 157Gd. The particle-core interaction usually dominated by a Coriolis coupling are accounted via first order perturbation theory [4]. The reaction cross section to each excited state in 156Gd is calculated as coherent contribution using a standard reaction code [5] based on spherical basis states. The spectroscopic factor associated with each state is the expansion coefficient of the deformed neutron state in a spherical Sturmian basis along with the spherical form factors [4]. The total cross section, as a function of the excitation energy, is generated using Lorentzian smearing distribution function. Our calculations show that, within the assumptions and computational modeling, the reaction 3He + 157Gd → 4He + 156Gd* has a smooth formation probability P(Jπ,E) within the energy range relevant to the desired reaction 155Gd + n156Gd*. The formation probability P(Jπ,E) resembles a Gaussian distribution with centroids and widths that differ for positive and negative parity states.

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