Fluorescence spectroscopy of C 60 in toluene solutions at 5 K

Abstract

We have recorded the dispersed fluorescence and the fluorescence excitation spectra of C 60 in toluene matrices at 5 K. Upon excitation with the green Ar + laser line ( λ=514 nm) we obtained for the first time in this matrix well resolved visible fluorescence spectra which we have compared with those observed in other low temperature matrices. Our spectra were interpreted and assigned using theoretical assessments of vibronic activities of transitions between the three lowest excited electronic states 1T 1g, 1T 2g, 1G g and the totally symmetric ground state, and on the basis of a single 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(1) progressions, Herzberg–Teller-induced h u and other ungerade mode vibrations, including a very active t 1u(4) mode. Excitation wavelength independent bands are assigned to the fluorescence of C 60 molecules in toluene microcrystals embedded in the toluene glass whereas excitation wavelength dependent features are interpreted as originating from C 60 molecules isolated in the toluene glass itself. These interpretations are supported by the results of spectrally selective detected fluorescence excitation spectra.