ABSTRACT
The nature and significance of the molecular transitions, shown as arrows in the diagram, are discussed in detail throughout this chapter. The states S0 and S1 are the ground state and lowest energy excited singlet electronic states, respectively, and T1 is the lowest energy triplet state for the molecule. Singlet and triplet states are distinguished by the
orientation of their electron spins.* The closely spaced levels within each electronic state represent the vibrational energy levels of the molecule, which are typically similar for the different electronic states. The different vibrational states are responsible for the characteristic shape of the absorption and emission spectral properties of a fluorescent molecule.
