Photoisomerization of azobenzene finds a wide range of applications in high-density storage devices , light-driven molecular motors and protein probes . Femtosecond spectroscopy revealed the important role of the low-lying excited states nπ * and ππ * in the course of isomerization . From the theoretical perspective, azobenzene's nonadiabatic dynamics initiated in the nπ * or ππ * states were investigated extensively 120, .