TABLE 5.
Comparison of the absorption peak positions between the experimental and calculated THz spectra and vibrational modes for NFD-INA form I and form II.
| Exp./THz | Cal./THz | Vibrational mode assignment | ||
|---|---|---|---|---|
| 295 K | 85 K | 0 K | ||
| Form Ⅰ | 0.98 | 1.14 | Collective; t (NFD) + ι (INA) | |
| 1.21 | 1.44 | Collective; ν (Ar) + ι (INA) | ||
| 1.54 | 1.63 | 1.71 | Collective; t (NFD) + ι (INA) | |
| 1.94 | 1.99 | Mainly from δ tw (-CH3) | ||
| 2.44 | 2.40 | Collective; ν (-CH3) + δ tw (INA) | ||
| 3.37 | 3.21 | Collective; ω (Ar) + δ tw (INA) | ||
| Form Ⅱ | 0.97 | 1.02 | 1.14 | Mainly from t (Ar) + t (-CH3) |
| 1.37 | Collective; t (NFD) + t (INA) | |||
| 1.52 | 1.59 | 1.65 | Mainly from t (-CH3) | |
| 1.88 | 2.37 | Collective; ν (-CH3) + ι (INA) | ||
| 2.30 | 2.69 | Collective; ν (-CH3) + ι (INA) | ||
| 2.45 | 2.87 | Collective; ι (NFD) + ι (INA) | ||
| 3.05 | 3.29 | Collective; ν (-CH3) + ι (INA) | ||
| 3.44 | 3.77 | Collective; ν (-CH3) + ι (INA) | ||
| 3.72 | 4.10 | Collective; ι (Ar) + ι (INA) |
ν, rotation; t, translation; ω, wagging; δ tw, twisting; ι, librational; -CH3, methyl group in NFD; Ar, aromatic ring.