Photochemistry and Jablonski Diagrams

A fluorescent dye has an absorption maximum at 490 nm and an emission maximum at 520 nm. (a) Calculate the energy of the absorbed and emitted photons. (b) Explain the Stokes shift using a Jablonski diagram. (c) The fluorescence quantum yield is 0.85 and the fluorescence lifetime is 4.2 ns. Calculate the radiative and non-radiative rate constants. (d) Explain the difference between fluorescence and phosphorescence in terms of spin states and lifetimes. (e) How does intersystem crossing lead to phosphorescence?