An upgraded algorithm for shell model calculations and its implementation in medium-heavy nuclei

A matrix diagonalization algorithm we developed in the past years has been revised and implemented for large scale shell model calculations using a spin uncoupled basis so as to obtain a sparse Hamiltonian matrix. The dimensions of such a matrix are reduced drastically by a procedure that combines an effective projection of the good angular momentum with an importance sampling specific of the method. Its numerical implementation on 116Sn illustrates the simplicity of the method and the fast convergence of the iterative procedure