Intruder level and deformation in the SD-pair shell model
  The influence of the intruder level on nuclear deformation is studied within the framework of the nucleon-pair shell model truncated to an SD-pair subspace. The results suggest that the intruder level has a tendency to soften the deformation and plays an important role in determining the onset of rotational behavior. 
Yan An Luo (1,2), Chairul Bahri (1,3), Feng Pan (1,4), and Jerry P.   Draayer (1) ((1) Department of Physics and Astronomy, ...