Application of the extended pairing model to heavy isotopes

Relative binding energies (RBEs) within three isotopic chains (Sn100-130, Yb152-181, and Pb181-202) have been studied using the exactly solvable extended pairing model (EPM) (F. Pan, V.G. Gueorguiev, J.P. Draayer, Phys. Rev. Lett. 92; 112503 (2004) (see also these proceedings)). The unique pairing strength G, which reproduces the experimental RBEs, has been determined. Within EPM, log(G) is a smooth function of the model space dimension dim(A), as expected for an effective coupling strength. In particular, for the Pb and Sri isotopes G can be described by a two parameter expression that is inversely proportional to the dimensionality of the model space, G.= alpha dim(A)(-beta) with beta approximate to 1.