The assignment of modes based on wavenumber.
| Wavenumber (cm−1) | Approximate description | ||||
|---|---|---|---|---|---|
| 755 | C8–H22 | Indole ring | Strong | In-plane | Stretch |
| C12–H25 | Medium | In-plane | Stretch | ||
| C5–H20 | |||||
| N6–H21 | In-plane | Stretch | |||
| 840 | H23–C9 | Ring | Strong | ||
| H22–C8 | |||||
| H20–C5 | Rock | Out-of-plane | |||
| 946 | H22–C8 | Ring | Strong | ||
| H23–C9 | Rock | Out-of-plane | |||
| 1208 | H24–O11 | Rock | Strong | In-plane | |
| H22–C8–H23–C9 | Scissor | In-plane | |||
| 1312 | C3–H19–H18 | Twist | Strong | ||
| H16–C2–H17 | Twist | ||||
| H20–C5 | Rock | In-plane | |||
| 1360 | H16–C2–H17 | Twist | Strong | ||
| H20–C5 | Rock | In-plane | |||
| 1433 | H16–C2–H17 | Wag | Strong | ||
| H18–C3–H19 | Wag | Medium | |||
| 1542 | H16–C2–H17 | Scissor | Strong | ||