What is diffraction?
Diffraction is the process by which a system of waves is spread out by interaction with matter. If we can create a lens, the diffracted waves can be used to recreate an image. Otherwise, we can only measure the waves and reconstruct using a computer.
Why do we need to use diffraction?
We need to see atoms, but they are too small to see with light. We need to use something with a small enough wavelength (e.g. x-rays, electrons or neutrons). We can’t build an x-ray or neutron microscope because we can’t make lenses for x-rays or neutrons. Therefore, we have to measure diffraction from the molecule and work backwards.
What are some common diffraction experiments?
- x-ray crystallography
- electron crystallography
- neutron crystallography
- x-ray powder diffraction
- small angle x-ray scattering (SAXS)
Why do we use cystals for diffraction?
Any interaction with an atom that can tell us about its position will also seriously affect that atom due to radiation damage. A solution to this is to observe lots of copies of the molecule at once by using a crystal.
What can we learn from x-ray crystallography?
- Bond lengths (atomic radii, bond orders)
- Bond angles, bonding densities (chemical bonding, molecular orbital theory)
- Surface structure (catalytic chemistry)
- Biological structure (biological function, drug design)
