two-photon resonance-ionization spectroscopy

Two-photon resonance-ionization spectroscopy (RIS) is a highly sensitive and selective analytical method that uses lasers to eject electrons from atoms or molecules, creating ions and free electrons. These charged particles are then detected to identify and quantify substances. Developed in the 1970s, RIS is valuable in physics, chemistry, and biology due to its ability to distinguish between different atoms and detect them at the single-atom level.123

The process involves using photons with specific energies to first excite an atom to a higher energy state, then a second photon completes the ionization. This stepwise approach ensures selectivity, as the laser must be tuned to the atom's specific energy levels. This technique allows for the detection of nearly every element in the periodic table. RIS has diverse applications, including dating materials, studying groundwater, measuring solar neutrinos, and analyzing trace elements in various fields.1423