Enhanced approach to the Eu3+ ion 5D0→7F0 transition intensity

•We examine the dependence of the 5D0→7F0 transition with the linear terms of the CF parameter for different mechanisms.•A dependence of the 5D0→7F0 transition with the polarizability of the Eu3+ ion is predicted.•The mechanisms studied have the same order of magnitude in some materials. The dependence of the 5D0→7F0 transition intensity with the linear terms of the crystal field parameter and polarizability of the Eu3+ ion is predicted. It is shown that the breakdown of the closure approximation mechanism is the most important one if the Eu3+ ion has a finite dipole moment in the ground state. The Eu:BFCl crystal is used for comparison with a satisfactory agreement.