| notation | experiment | calculation | |||||||
|---|---|---|---|---|---|---|---|---|---|
| vibration | rotation | gas-phase | neon | argon | krypton | xenon | harmonic | anharmonic | |
ν3[F2] |
νasCH |
R(1) | 3038.5 | 3027.1 | 3040.9 | 3030.0 | 3018.3 | ||
| R(0) | 3028.8 | 3027.4 | 3037.3 | 3026.5 | 3013.3 | ||||
| R(0)' | n.a. | 3020.0 | 3033.5 | 3022.2 | n.a. | ||||
| Q | 3018.8 | 3018.6 | 3029.2 | 3018.8 | 3005.3 | 3163.7 | 3024.5 | ||
| P(1) | 3009.0 | 3014.9 | 3022.2 | 3010.1 | 2995.6 | ||||
| ν1[A1] | νsCH | Q | 2917 | n.a. | n.a. | 2915.7 | 2905.4 | 3040.8 | 2919.6 |
| ν2[E] | δasCH | Q | 1534 | n.a. | n.a. | n.a. | n.a. | 1572.3 | 1533.9 |
ν4[F2] |
δsCH |
R(1) | 1316.8 | 1309.5 | 1309.8 | 1306.9 | 1304.8 | ||
| R(0) | 1311.4 | 1308.4 | 1306.6 | 1303.4 | 1300.7 | ||||
| R(0)' | 1307.3 | 1305.9 | |||||||
| Q | 1305.8 | 1306.3 | 1302.7 | 1299.1 | 1295.7 | 1346.8 | 1312.1 | ||
| P(1) | 1300.3 | 1303.9 | 1298.7 | 1294.8 | 1290.9 | ||||
Note: The frequencies of the molecular vibrations are given in wavenumbers cm-1.
• The notation of rotational-vibrational transitions indicates, above all, whether the transition is found in the P-, Q-, or R-branch. The number in the brackets stands for the change in the rotational quantum number ΔJ = J' - J'' caused by the state transition, where J' indicates the target state and J'' the initial state. Consequently, the rotational transitions (J' ← J'') are labeled as R(J'') for ΔJ = +1, as Q(J'') for ΔJ = 0, and as P(J'') for ΔJ = -1.
• Methane's spectrum has been studied in matrices of neon ( Dinu 2020, ??), argon ( Dinu 2020, ??), krypton ( ??) and xenon ( ??), among others ( ??).
• There are systematic rotational-vibrational transitions assignable in matrix-isolation infrared spectra.
• Methan is not considered to occupy different cages within solid matrices ??
• Anharmonic frequencies are form vibrational self-consistent field and configuration interaction (VSCF/VCI) calculations relying on a 3-mode potential energy surface using CCSD(T)/aug-cc-pVTZ energies, see Dinu 2020.