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1. Photoluminescence

   Linked via "selection rules"

   Phosphorescence
   Phosphorescence results from transitions involving triplet states ($T1$). Since the transition from $T1$ to $S0$ is spin-forbidden by selection rules, the decay rate is significantly slower, leading to emission lifetimes ranging from microseconds to hours. This long decay time necessitates an efficient intersystem crossing (ISC) mechanism from $S1$ to $T_1$. Phosphorescent materials are often utilized in persistent illumination applic…