Question: what are the different types of spectroscopy and what do they all do?

Andrew McKinley answered on 17 Nov 2014:

There are soooo many different types it’s difficult to keep track! At its core, spectroscopy can measure anything about a molecule when the molecule changes energy states. There are 4 types of energy states; in order of increasing energy:

– Nuclear (a nucleus in a magnetic field flipping up and down)
– Rotational (the molecule rotating in space)
– Vibration (the bonds in the molecule vibrating like a spring)
– Electronic (the electrons in the molecule hopping about – this is what I do)

With nuclear spectroscopy, you can learn about the electric field around the molecule, as this affects the magnetic field around the nucleus. Each atom has a signature field, and this helps you unravel the structure of the molecule.
– Rotational spectroscopy allows you to measure bond-lengths and determine masses of the atoms in simple molecules. This is used a lot by astrochemists (chemists interested in molecules in space)
– Vibration spectroscopy helps you to identify “functional groups”, as each bond has a characteristic vibration frequency (look at each bond as a spring – some springs are stronger than others).
– Electronic spectroscopy helps you to learn about the environment that the molecule is in, and study things such as the effect of different solvents (water, ethanol, propanone etc)

Within any one type of spectroscopy, there are loads of different techniques used, and I’m not sure that they can be listed here!