Anomalous fluorescence of terrylene in neon matrix

Fluorescence and fluorescence excitation spectra of terrylene deposited in Ne and Ar matrixes at 7 K have been studied. The (0,0) fluorescence band of terrylene in Ne matrixes is shifted by 330 cm(-1) to low energy with respe ct to the (0,0) fluorescence excitation band observed at 18990 cm(-1). Furt hermore, the vibronic structures of both spectra are different. In contrary to this observation, the fluorescence and fluorescence excitation spectra of terrylene in Ar matrixes have a common origin at 18312 cm(-1) and demons trate mirror symmetry. Semiempirical AM1 calculations combined with the ana lysis of the vibronic structure of the spectra suggest that terrylene molec ules in the excited S-1 state are subject to relaxation. This relaxation is possible in soft Ne but it is frozen in rigid Ar matrix.