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Atomic emission spectroscopy measures the energy of atoms in a sample by adding energy to see what happens to the atoms. The machine recognizes the light energy and calculates the concentrations of individual elements. Samples must be decomposed into free atoms, and each element produces a distinctive set of photons. Atomic absorption spectroscopy works on the same principles but reads the amount of light energy the sample absorbs.
Atomic emission spectroscopy (AES) is an analytical technique that measures the energy of atoms in a sample. Central to this method is adding energy to a sample to see what happens to the atoms already there. Individual elements produce slightly different beams of light energy after the extra energy temporarily alters the atom. The reader portion of an atomic emission spectroscopy machine recognizes the light energy coming from the sample, and the computer portion of the machine calculates the concentrations of individual elements in a sample from the wavelengths of incoming light.
Every element in the world, in its simplest form, is a single atom, although many occur in nature as multiple atoms stuck together or in combination with other elements. Atoms are tiny particles that typically have small particles called protons and neutrons locked together in a central nucleus known as the nucleus. The smallest particles called electrons also continuously surround the nucleus.
Electrons move around the nucleus in a specific way. Similar to hula hoops of different diameters, electrons only circulate in specific diameters, with some in smaller diameter orbitals and some in larger diameter orbitals. Usefully for atomic emission spectroscopy, however, each electron can jump to a higher orbital if enough ambient energy is present.
Samples for AES analysis often contain mixtures of elements and compounds such as soil for example. An atomic emission spectroscopy machine, however, can only read individual atoms. Therefore, when an analyst prepares a sample for AES testing, he must decompose all the molecules of the compound into free atoms. Typically, the analyst turns the sample into an aerosol by adding energy from sources such as ovens, lasers, or sparks.
The extra energy from the source that breaks the sample is also the energy acting on the electrons in the sample elements. With the extra energy, the electrons jump into higher orbitals. When they fall back after the energy has dissipated, the energy they had stored from the source emits as photons of light. Photons are like little packets of energy.
Every spectroscopy machine has a detector that recognizes the presence of energy and transmits that information to a computer program that converts the raw data into clearer descriptions. In the case of an AES machine, the detector reads the presence and intensity of individual photons. Intensity is related to the wavelength of light, and each element in the sample has a distinctive set of photons that would produce specific wavelength readings. From the photons, therefore, the machine can understand which elements, and how many of each, are present in a single sample.
Another method for analyzing the elemental composition of samples is atomic absorption spectroscopy (AAS). It works on the same principles as the AES, but instead of reading the light emitted by an energized sample, the machine reads the amount of light energy the sample absorbs as an indication of the type and amount of electrons in the sample. AAS is suitable for gas samples.
