Experimental evidence for far configuration mixing effects on off-diagonal hfs interaction between the (3d+4s) N+2 configurations of free atoms

In our systematic investigations on the hyperfine structure (hfs) of high lying metastable states in 3d-shell atoms we have found evidence for an extraordinary strong far configuration mixing effect on off-diagonal matrix elements between configurations. Using theABMR-LIRF method the hfs of (3d ² 4s ²)³ P ⁴⁷Ti, (3d ³ 4s ²)⁴ P ⁵¹V (3d ⁵ 4s ²)⁴ G ⁵⁵Mn and (3d ⁶ 4s ²)³ H ⁵⁷Fe has been measured. Values found for the effective radial parameters (a^{k_s k_l } ) of the magnetic dipole interaction disagreed up to 300% with those known from hfs measurements of lower lying multiplets of the same configuration, even when intermediate coupling and electrostatically correlated second order hfs effects within each of the configurations are taken into account. We suggest that the main part of these discrepancies can be explained, if two-body core polarization is considered, which screens the ordinary one-body core polarization parametera _3d ¹⁰ . Preliminary values for the corresponding parameters are given.