| C3 | C6 | C8 | Ref. |
|---|---|---|---|
| -5.503 | 1.401[3] | 1.021[5] | M. Marinescu and A. Dalgarno, Phys. Rev. A 52, 311 (1995) |
| -5.510 | 1.301[3] | 9.920[4] | B. Bussery and M. Aubert-Frecon, J. Chem. Phys. 82, 3224 (1985) |
| -5.494 | 1.374[3] | 9.987[4] | F. Vigne-Maeder, Chem. Phys. 85, 139 (1984) |