If no chemical process occurs, the hot, isolated molecule is expected to cool down due to blackbody radiation. Since the seminal papers by Sellgren and Leger and Puget, 12 some specific near-infrared (IR) spectral features of interstellar dust have been assigned to polycyclic aromatic hydrocarbons (PAHs). These earlier works raised the hypothesis that those IR features arise from small, 5-10 Å molecules instantaneously heated to about 1000 K by UV radiation.