Multiple emissions of α-naphthil: fluorescence from S₂ state

Abstract

Multiple emissions of α-naphthil are reported in solution phase at room temperature as well as in ethanol glassy matrix at 77 K, frozen under different conditions of illumination. Steady state and time-resolved fluorometric measurements are undertaken to assign the observed emissions to the different species in terms of geometry and electronic states of the fluorophore. The unexplored emission band peaking at 423 nm has been ascribed to originate from the S₂ electronic state. Exhaustive experiments reveal that while the trans conformer of α-naphthil gives only the S₁ emission, the conformation with a geometry close to the ground state one emits from both S₁ and S₂ electronic states depending on the excitation wavelength.