Non-planar distortion of single molecules revealed by vibronic fluorescence excitation: Terrylene in p-terphenyl and naphthalene crystals

Fluorescence excitation spectra of spatially resolved single terrylene molecules in p-terphenyl and naphthalene crystals were studied at 5 K. The observation of a single vibronic line at 251 ± 4 cm−1 above the purely electronic line indicates that the terrylene molecules in p-terphenyl crystals are planar in the S1 excited state. The observation for terrylene in naphthalene crystals of two vibronic lines located 239 ± 2 and 252 ± 2 cm−1 above the purely electronic origin in naphthalene crystals indicates that there is non-planar distortion of the terrylene skeleton. The fully saturated fluorescence detection rate for the purely electronic (0, 0) transition was found to be about two times smaller than that for the vibronic components.