| C3 | C6 | C8 | Ref. |
|---|---|---|---|
| -20.95 | 1.739[4] | 1.656[7] | M. Marinescu and A. Dalgarno, Phys. Rev. A 52, 311 (1995) |
| -24.27 | 2.609[4] | 2.451[7] | B. Bussery and M. Aubert-Frecon, J. Chem. Phys. 82, 3224 (1985) |
| -21.53 | 1.951[4] | 1.625[7] | F. Vigne-Maeder, Chem. Phys. 85, 139 (1984) |