Slides

Vibrational Motions
• High-­‐frequency:
– Examples: νX-­‐H (νO-­‐H, νS-­‐H, νN-­‐H, νC-­‐H, ...)
– Wavenumbers: 2800 – 3600 cm -­‐1
– Frequencies:
– Vibra4onal periods:
• Intermediate frequencies:
– Examples: νC=O, δOH, aroma4c ring vibra4ons, ...
– Wavenumbers: ˜ ν = 400-­‐1800 cm -­‐1
– Frequencies:
ν ≈1.2⋅ 10 13 5.4⋅ 10 13 s −1
– Vibra4onal periods: T = 83 -­‐ 18 fs
• Low frequencies:
˜ ν =
– Examples: intermol. modes, e.g. hydrogen bond modes, ...
– Wavenumbers: 10-­‐400 cm -­‐1
– Frequencies:
– Vibra4onal periods: T = 3 ps -­‐ 83 fs
m
ν = ˜ ν ⋅ c = 3000⋅ 10 8 s ⋅ 1
10 −2 m = 9⋅ 1013 s −1
T = 1 ν ≈11⋅ 10−15 s =11fs
˜ ν =
ν ≈ 0.03⋅ 10 13 1.2⋅ 10 13 s −1