Correlation holes and wavefunctions for the 1S, 1P°, and 3P° states of Be, B+, and C2+

``Average'' pair distribution functions, P(r12), are calculated both from the Hartree-Fork (HF) and configuration interaction (CI) wavefunctions for the 1P°, 3P°, and 1S states of Be, B+, and C2+. The average electronic separation, , and interelectronic interaction energy, , are also obtained from the CI and HF wavefunctions. Reflecting the difference of the degree of correlation (between the CI and HF wavefunctions), the CI wavefunctions give a larger interelectronic distance than the HF wavefunctions except for the 1P° state of Be. For Be 1P°, the CI wavefunction reduces the average electronic separation in comparison with the HF wavefunction; this contradicts the general idea that the calculated electron pair distribution function for a CI wavefunction is more spread out than for the HF counterpart. This reduction of is discussed in connection with the fact that the 2p orbital obtained by the HF calculation in Be 1P° is much more diffuse that that in the other states and that the 2p electron distribution is contracted by the CI calculation. Apart from Be 1P°, the difference between the two functions, P(r12), calculated from the CI and HF wavefunctions, gives a shallower correlation hole for 3P° than for 1P° and 1S. This is because in the HF calculation the Pauli principle keeps the L-shell electrons apart in the triplet state.