Interelectronic angles of group 14, 15, and 16 atoms in their low-lying multiplet states

The average interelectronic angles 〈θ_12〉 in position space and 〈θ¯_12〉 in momentum space are examined for the multiplet states arising from the ground electronic configurations of the group 14, 15, and 16 atoms. The angles 〈θ_12〉 and 〈θ¯ _12〉 are greater than 90 degrees with no exceptions and two electron vectors prefer inverse directions to the same direction on average. Common to all 15 atoms, it is found that in position space, lower multiplets have larger interelectronic angles 〈θ_12〉 than higher multiplets. However, the opposite is true in momentum space and the interelectronic angles 〈θ¯_12〉 are smaller in lower multiplets. The differences in the angles Δ〈θ_12〉 and Δ〈θ¯_12〉between multiplets have good linear correlations with the relative stability ΔE of the multiplets