Nucleon-pair shell model: Formalism and special cases

Abstract

A formalism is described for a nucleon-pair shell model (NPSM) for even-even and even-odd nuclei. The building blocks of the model space are collective nucleon pairs of angular momenta J = 0,2,… for an even system, and nucleon pairs plus one unpaired nucleon for an odd system. Analytical formulas are given for the matrix elements of a general Hamiltonian. Without any space truncation, the NPSM is equivalent to the shell model in full space, while with a special choice for the building blocks and Hamiltonian it reduces to the broken pair model, the favored-pair model of Hecht and the fermion dynamical symmetry model.