ETD

• cation sensor
• dye sensor
• LSC

So, when the molecule finally arrives at the lowest vibrational level of the S1 electronic state (after only 10-12 s) fluorescence is emitted. Fluorescence usually takes place in 10-10 to 10-8 s, depending on many factors as the environment of the chromophore, the presence of dynamic quenching, or energy transfer. If the molecule fluoresces, it returns to one of many different higher vibrational levels of the S0 state. It is worthy to highlight that photons emitted by fluorescence have a lower energy than the initial excitation photons due to the competition at different energy levels between radiative and non-radiative decay pathways during electron descent ot the ground state as previously discussed. This energy gap is called the Stokes shift.