Atomic emission spectroscopy

Scientists use light to learn what materials are made of. This method is called atomic emission spectroscopy.

It works by looking at the light that atoms give off. Every element has a unique atomic arrangement. Because of this, each element creates its own special pattern of light. These patterns are called spectral lines. The specific wavelength of a line tells us the identity of the element. The intensity, or brightness, of the light tells us how much of that element is in the sample.

To see these lights, we must first excite the atoms. This means we give them energy. We can use a flame, a spark, or even plasma. When an element is burned in a flame, its atoms move from a ground state to an excited state.

As those atoms move back down to their ground state, they emit electromagnetic radiation. This radiation can be measured as light. A device called a monochromator can disperse these wavelengths so we can see them. We can even use the width of these lines to learn about an atom's temperature.

Two scientists named Robert Bunsen and Gustav Kirchhoff first used this as a tool. They established it as an important way to do chemistry.

Since then, the tools have changed a lot. One modern way uses something called inductively coupled plasma, or ICP-AES. This method uses a coil of wire with an electric current. This current creates a magnetic field inside a quartz tube. This field puts energy into a plasma. Plasma is a collection of charged particles like cations and electrons.

Using plasma is very helpful because it is much hotter than a flame. These high temperatures help create more excited atoms. In ICP-AES, we often use liquid samples. A peristaltic pump moves the liquid into a nebulizer. The nebulizer turns the liquid into a fine mist. Only the finest droplets enter the plasma with the argon gas. This method is great because it can detect many different elements at once. It also provides a very stable and reproducible signal for scientists to study.

We can also use sparks or arcs to study solid metal samples. This is common in places like metal casting facilities to check quality. For materials that do not conduct electricity, we can mix them with graphite powder. This makes the sample conductive so the spark can pass through it. This helps us understand the chemical makeup of many different mixtures. Whether using a simple flame or a high-tech plasma, light helps us see the tiny building blocks of our world.