Splitting scheme of the singlet excited states

Figure 6. Energy level scheme for a typical aromatic hydrocarbon. So denotes the electronic ground state, S the first excited singlet state and T the first excited triplet state. The triplet state is actually split into three sublevels by magnetic dipolar interaction of the triplet electrons (zero-field splitting). The dots and arrows denote the approximate populations and lifetimes of the sublevels for a typical, planar aromatic hydrocarbon. The lower panel shows schematically the time distribution of fluorescence photons (photoelectric pulses) for a single emitter undergoing singlet-tiiplet transitions leading to photon bunching.

Fig. 34. Magnetic susceptibility of UPCI2AI3 for field parallel to a- and c-axis. The pronounced maximum for XJ ( ) is a typical signature of CEF split localised 5f-states (Grauel et al., 1992). The full line is a fit using a CEF level scheme containing singlet ground state and first excited state (33 K).

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