Practice question

Jablonski diagram organizes electronic states by multiplicity and energy. Upon photon absorption electron jumps from ground singlet S0 to excited singlet S1 or higher S2, then undergoes rapid internal conversion and vibrational relaxation to lowest vibrational level of S1 within picoseconds conserving spin. Fluorescence represents radiative transition from S1 lowest vibrational level to various vibrational levels of S0, emitting photon with longer wavelength and nanosecond lifetime. This distinguishes fluorescence S1→S0 from phosphorescence T1→S0 which is spin-forbidden slower, and from nonradiative S2→S1 internal conversion steps that do not emit light.