In its purest sense, spectroscopy is understood to be the interaction between energy and matter as a function of wavelength – but don’t let that put you off. Spectroscopy is an amazing technique for studying the properties of matter; it helps astronomers explore space, reveals the molecular structure of our natural world, and it produces some pretty cool pictures too.
There are three key types of spectroscopy; X-ray fluorescence (XRF) is just one of them. To understand exactly how XRF works, you first need to know a few of the fundamentals: the universe is made up of atoms and inside those atoms are electrons. Each element – hydrogen, oxygen, carbon – has its own atomic fingerprint, because the arrangement of electrons is different for each.
So that’s atoms, now for light: all types of light are made up of a spectrum of different colours. That’s why when the sunlight hits raindrops the light is dispersed and you end up with a rainbow. There are different types of light, including visible, infrared, and X-ray light. All light moves in peaks and troughs like waves, and the different types of light have different wavelengths. For XRF, we need X-rays because their small wavelength is able to pick up individual atoms in material.
When X-ray light passes through an atom, some of the colours of light will be absorbed by the electrons and some will pass straight through. Which colours are absorbed is determined by the arrangement of the electrons inside the atom; this means that different elements absorb different colours. So if you shine X-rays onto a sample, different colours will come out of the other side depending on what elements are in the sample.
Scientists use XRF to determine the elements present in various materials. The technique can be used on something smaller than a grain of sand or as large as a planet. From stars to rainbows, spectroscopy often reveals nature at its best and most beautiful.
Diamond Light Source is the UK's national synchrotron science facility, located at the Harwell Science and Innovation Campus in Oxfordshire.
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