| C3 | C6 | C8 | Ref. |
|---|---|---|---|
| -6.128 | 2.636[3] | 2.171[5] | M. Marinescu and A. Dalgarno, Phys. Rev. A 52, 311 (1995) |
| -6.480 | 2.669[3] | 2.301[5] | B. Bussery and M. Aubert-Frecon, J. Chem. Phys. 82, 3224 (1985) |
| -6.225 | 2.686[3] | 2.100[5] | F. Vigne-Maeder, Chem. Phys. 85, 139 (1984) |