Atomic absorption spectroscopy is a commonly used technique for the determination of single elements in compounds. As the name suggests, the particles must be atomized in order to perform analysis. After the compound has been atomized (usually by a flame), a radiation source produces waves that pass through the substance and are received by a detector. The most common light sources are hollow cathode lamps, and the most common detectors are photomultiplier tubes. Both of these elements of the instrument are further explained under sources and detectors. This type of spectroscopy has been around for over fifty years, and it remains one of the most common instrumental analysis techniques for single elements.