Describing Neutron Transfer Reactions for Deformed Nuclei with a Sturmian Basis

Highly excited states in 156Gd, populated via the neutron pickup reaction 157Gd(3He,4He)156Gd, are investigated, and their spin–parity distribution P(Jπ,E) is examined. The cross section for one-neutron transfers to states above the neutron separation energy in 156Gd is calculated as coherent sum, using standard reaction codes that employ spherical basis states. Spectroscopic factors and form factors for the relevant states are obtained by expanding the deformed neutron wave functions in a spherical Sturmian basis. For the energy regime relevant to surrogate applications involving neutron absorption, 155Gd+n →156Gd⋆, the calculations show that the reaction 3He+157Gd →4He+156Gd⋆ induces a well-behaved formation probability P(Jπ,E) of approximately Gaussian shape. It is observed that the centroid and shape of the Gaussian distributions of the positive and negative parity states of the compound system can be significantly different from each other!