Core Technology & Physics
Excitation
Putting the energy in–the absorbed photon every fluorescence measurement starts with.
Definition
Excitation is the absorption of a photon that lifts a fluorophoreLoading... from its ground state to a higher-energy electronic state. The molecule remains there for a few nanoseconds–its fluorescence lifetimeLoading...–before returning. Only wavelengths the fluorophore absorbs will excite it, which is what makes channels separable. In FRETLoading... the donor is excited and the acceptor is not: acceptor signal under donor excitation is the evidence that transfer occurred.