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Resonance-ionization spectroscopy (RIS) is a spectroscopic method that uses resonant laser excitation to promote an atom or molecule above its ionization potential to create an ion. The ions are detected as a current by a biased collector or by a mass spectrometer. RIS is useful to study the electronic structure of atoms or molecules and to make quantitative measurements of analyte concentrations. For more information see the document on RIMS.
Laser-enhanced ionization (LEI) ionizes atoms in a flame. It relies on resonant laser excitation of an atom to a higher electronic excited state. The excited atom is then ionized by collisions in the flame. The ions are collected by biased wires or plates in or near the flame. The LEI method produces lower limits of detection for several elements.
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