TABLE I.
The low-lying intermolecular vibrational energy levels in cm−1 of the CO2 cyclic trimer obtained with the harmonic approximation, as well as VSCF, VMP2, and VCI methods.
| HAR | HAR | VSCF | VMP2 | VCI | |||
|---|---|---|---|---|---|---|---|
| CCSD(T)-F12b/aVDZ | mbCO2 | mbCO2 | mbCO2 | mbCO2 | Experimenta | Theoryb | |
| ν1(E″)c | 16.9 | 11.0 | 15.9 | 12.0 | 13.5 | 12.301 | |
| ν2(E″)c | 10.75 | 11.4 | 16.6 | 12.3 | 15.7 | ||
| ν3(A″) | 25.58 | 19.6 | 24.2 | 21.0 | 22.2 | 18.7 | 22.4 |
| ν4(E′)c | 60.12 | 51.8 | 49.5 | 44.1 | 49.8 | ||
| ν5(E′)c | 58.12 | 52.4 | 49.9 | 43.0 | 49.1 | ||
| ν6(E′)c | 68.82 | 58.2 | 53.9 | 55.4 | 54.6 | ||
| ν7(E′)c | 66.34 | 58.8 | 54.4 | 54.6 | 53.9 | ||
| ν8(A′) | 77.43 | 65.5 | 59.9 | 57.2 | 59.4 | ||
| ν9(A′) | 108.59 | 99.5 | 87.9 | 94.5 | 91.3 |