Abstract
Reduced transition probabilities
B(E2) for spherical doubly even nuclei are calculated in the quasiboson approximation (QBA), the random-phase approximation (RPA) and the improved random-phase approximation (IRPA). A comparison is made with experiments for each approximation, and the effect of the Pauli principle is demonstrated. The effect of these approximations on the systematics is studied by comparing the average of the absolute deviations from the experimental values for each approximation. The problem is formulated by using double-time Green function techniques.