Do molecules have a characteristic frequency or natural oscillation, similar to a bridge or building?

Question

If it has, how can it be calculated and/or determined?

Answer 1

The absorption spectrum of a molecule tells you something about its energy states, related to the quantum states of the outer shell electrons. It tells you nothing about oscillations within the molecule. Consider a simple O2 oxygen molecule. Electrostatic repulsion between the two positively charged nucleii tends to push them apart. The binding force of the electrons orbiting both nucleii tends to pull them together. Think of two balls with a spring pushing them apart and a rubber band pulling them together. For this simple molecule, it's a simple mechanical resonance problem. For more complex molecules with multiple bonds, the calculations get much harder.

Answer 2

They often have several natural frequencies. These usually depend on the energies of the bonds between the atoms of the molecules. These energies often correspond to the same energy in a photon in the infrared spectrum, at least for organic molecules. A common way of determining the chemical composition of an unknown material is to shine an infrared light on the material and measure the frequencies that get absorbed. By comparing the absorbed frequencies with known values for standards, one can determine exactly what chemicals, or atr least what chemical bonds, are present.