Practice question

In Jablonski representation, absorption excites an electron from ground S0 to vibrationally excited levels of S1. Rapid internal conversion and vibrational relaxation bring the molecule to the lowest S1 level within picoseconds, following Kasha rule. Fluorescence is the radiative return from this relaxed S1 state back to various vibrational levels of S0, emitting a photon of lower energy. S0 to S1 represents absorption, S1 to T1 denotes intersystem crossing, and T1 to S0 yields delayed phosphorescence. Only S1 to S0 corresponds to prompt fluorescence.