M. Thoresen et al., COMPARISON OF TECHNIQUES FOR COMPUTING SHELL-MODEL EFFECTIVE OPERATORS, Physical review. C. Nuclear physics, 57(6), 1998, pp. 3108-3118
Different techniques for calculating effective operators within the fr
amework of the shell model using the same effective interaction and th
e same excitation spaces are presented. Starting with the large-basis
no-core approach, we compare the time-honored perturbation-expansion a
pproach and a model-space truncation approach. Results for the electri
c quadrupole and magnetic dipole operators are presented for Li-6. The
convergence trends and dependence of the effective operators on diffe
ring excitation spaces and Pauli Q-operators are studied. In addition,
the dependence of the electric-quadrupole effective charge on the har
monic-oscillator frequency and the mass number, for A = 5,6, is invest
igated in the model-space truncation approach.