Figure 10.3 Stretching and bending vibrations in molecules |
Hooke’s law and frequency of vibration
We have seen that the bonds are not static but vibrating in different ways. A vibrating bond can therefore be considered a spring with its ends tethered to two atoms (Figure 10.4).
Figure 10.4 Spring analogy of a bond vibration |
If the masses of the atoms are m1 and m2, the frequency of stretching vibration of the diatomic molecule can be given by the Hooke’s law:
..............................................................................(10.1)
where, ν is the frequency of vibration, k is the spring constant, and μ is the reduced mass i.e. 
Dividing equation 10.1 by λ gives:
............................................................................(10.2)