Relation between emission spectrum and excitation wavelength

Relation between emission spectrum and excitation wavelength 

Jablonski diagram reveals that emission occurs from the excited state Si. Therefore, emission is in principle independent from the excitation wavelength. In another chapter we are going to see that this is not always the case. 

Emission occurs with lower energy than absorption, and not all the molecules present at the excited states are going to participate in the fluorescence. Therefore, a fluorescence quantum yield cpp exists and is equal to  

Equation 2.12 describes the relation that exists between the fluorescence intensity at a precise emission wavelength and the intensity of the incident light (lo), the quantum yield of the fluorophore and the optical density of the fluorophore at the excitation wavelength. 

Apparently, the fluorescence intensity increases linearly with all these parameters. However, we are going to see the limits of this linearity especially when experiments are performed at high optical density. 

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