| C3 | C6 | C8 | Ref. |
|---|---|---|---|
| -12.26 | 4.094[3] | 2.120[6] | M. Marinescu and A. Dalgarno, Phys. Rev. A 52, 311 (1995) |
| -12.95 | 4.144[3] | 2.421[6] | B. Bussery and M. Aubert-Frecon, J. Chem. Phys. 82, 3224 (1985) |
| -12.51 | 4.164[3] | 2.078[6] | F. Vigne-Maeder, Chem. Phys. 85, 139 (1984) |