two-photon photochromism

https://doi.org/10.1351/goldbook.TT07491
Photochromic process involving a @T06542@. The process might involve the simultaneous or the sequential absorption of two photons.
Source:
PAC, 2007, 79, 293. (Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)) on page 436 [Terms] [Paper]