I heard that the intensity-dependence on the PL of the one-photon absorption is generally linear.
However, the intensity of PL at two-photon absorption increases to the quadratic power of the laser intensity. And three-photon does third power of the laser intensity.
Can you teach me a theoretical explanation?
Thank you.
In normal absorbtion matter interacts with one photon at time, so this interaction has linear function to response to light.
In higher order absorbtion matter interacts with multiphotons at "same time".
In other words, you can imagine everything like kinetic reaction of matter with light, where matter is used in excess. In the case of normal absorbtion you have pseudo first order kinetics, because the reaction depends only on amount of photon A1. In case of multiphoton absorbtion you will have two reagents photons A1 and A2, so it will be pseudo second order reaction.
Mykhailo Bondarchuk Thank you for the answer. I found many paper using the MPA, however, I could not found the exact equation and theory about MPA. Is there any?
Try to check this one, if you need very brief theory:
Ma, ZC., Chen, QD., Han, B. et al. Measurement of Two-Photon Absorption Cross Section of Metal Ions by a Mass Sedimentation Approach. Sci Rep 5, 17712 (2016). https://doi.org/10.1038/srep17712
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