Infrared spectroscopy

• Atoms and molecules are joined by covalent bonds, which have energy and vibrate naturally around a central point. The amount of vibration increases with increasing temperature. The bonds can absorb infrared radiation, which makes them bend or stretch more.
• One type of vibration, a stretch, is a rhythmic movement along the line between the atoms so that the distance between the two atomic centers increases and decreases. The second type of vibration, a bend, results in a change in bond angle.
• The amount that a bond stretches or bends depends on:

  • the mass of the atoms in the bond- heavier atoms vibrate more slowly than light atoms
  • the strength of the bond- stronger bonds vibrate faster than weaker bonds