Term: two-photon excitation
https://doi.org/10.1351/goldbook.T06541

Definition:
Excitation resulting from successive or simultaneous absorption of two photons by an atom or molecular entity. This term is used for successive absorption only if some of the excitation energy of the first photon remains in the atom or molecular entity before absorption of the second photon. The simultaneous two-photon absorption can also be called biphotonic excitation.

Related Terms:
1) excitation energy (http://doi.org/10.1351/goldbook.E02250).
2) biphotonic excitation (http://doi.org/10.1351/goldbook.B00668).
3) two-photon process (http://doi.org/10.1351/goldbook.T06542).

Source: PAC, 1996, 68, 2223. 'Glossary of terms used in photochemistry (IUPAC Recommendations 1996)' on page 2282 (https://doi.org/10.1351/pac199668122223)

Citation: 'two-photon excitation' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.T06541

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