| C3 | C6 | C8 | Ref. |
|---|---|---|---|
| -9.202 | 8.047[3] | 1.132[6] | M. Marinescu and A. Dalgarno, Phys. Rev. A 52, 311 (1995) |
| -10.06 | 1.135[4] | 6.744[5] | B. Bussery and M. Aubert-Frecon, J. Chem. Phys. 82, 3224 (1985) |
| -9.400 | 8.407[3] | 1.011[6] | F. Vigne-Maeder, Chem. Phys. 85, 139 (1984) |