Thermal relaxation process of a vibrational excess energy of similar to2800 cm(-1) deposited on nu' = 2 level of ring-breathing mode has been investigated on S-1 perylene and S-1 12-(3-perylenyl)dodecanoic acid in 2-methyltetrahydrofuran at room temperature. The Franck-Condon analysis of femtosecond time-resolved fluorescence spectra indicated that noticeable vibrational transients exist at nu' = 2 level even a few picoseconds after photoexcitation. It was confirmed that the population distribution over nu' = 0, 1, 2 levels is non-Boltzmann type at early time stage and converges into Boltzmann type with a few picoseconds time constant. (C) 2003 Elsevier Science B.V. All rights reserved.