Fluorescence spectroscopy of C-60 in toluene solutions at 5 K

We have recorded the dispersed fluorescence and the fluorescence excitation spectra of Coo in toluene matrices at 5 K. Upon excitation with the green Ar+ laser line (lambda = 514 nm) we obtained for the first time in this mat rix well resolved visible fluorescence spectra which we have compared with those observed in other low temperature matrices. Our spectra were interpre ted and assigned using theoretical assessments of vibronic activities of tr ansitions between the three lowest excited electronic states T-1(1g), T-1(2 g), (1)G(g) and the totally symmetric ground state, and on the basis of a s ingle 0(0) level which has pseudo-Jahn-Teller (JT) components of the three near-degenerate excited states. The fluorescence spectra exhibit prominent JT induced h(g)(l) progressions, Herzberg-Teller-induced h(u) and other ung erade mode vibrations, including a very active t(lu)(4) mode. Excitation wa velength independent bands are assigned to the fluorescence of C-60 molecul es in toluene microcrystals embedded in the toluene glass whereas excitatio n wavelength dependent features are interpreted as originating from C-60 mo lecules isolated in the toluene glass itself. These interpretations are sup ported by the results of spectrally selective detected fluorescence excitat ion spectra, (C) 2001 Elsevier Science B.V. All rights reserved.