Intershell nl4f electron correlation effects

The pair correlation energies for some nl 4 f pairs of the ground state of the Yb atom are calculated for the first time. The partial wave ( PW ) increments to the second‐order pair energies are generated using numerical first‐order radial pair functions obtained as the solution of two‐dimensional differential equations. The analysis of the PW s contributions shows the dominant role of the df , fg , and gh PW s for the 4 d 4 f pair, of the pf and dg PW s for the 4 p 4 f and 5 p 4 f pairs, and of the sf and pg PW s for the 4 s 4 f , 5 s 4 f , and 6 s 4 f pairs. A discussion of the similarities and differences of the structure of the correlation energy found in this paper with those calculated earlier for smaller atoms is given.