Interatomic potential for the X¹Σ state of Be₂, revisited

An extended geminal model has been applied to determine the interatomic potential for the X 1 Σ state of Be 2 . By adopting a (23 s , 10 p , 8 d , 6 f , 3 g , 2 h ) uncontracted Gaussian‐type basis, the following spectroscopic parameters are obtained: R e = 4.633 a.u. (4.63 a.u.), D e = 945 ± 15 cm (790 ± 30 cm), G (1)– G (0) = 221.7 cm −1 (223.8 ± 2 cm −1 ), G (2)– G (1) = 175.0 cm −1 (169 ± 3 cm −1 ), G (3)– G (2) = 123.1 cm −1 (122 ± 3 cm −1 ), and G (4)– G (3) = 80.8 cm −1 (79 ± 3 cm −1 ), experimental values in parentheses. The calculated binding energy is substantially higher than the accepted experimental value.