FEMTOSECOND DYNAMICS OF PHOTOINDUCED DARKENING IN C-60 FILMS

Femtosecond laser spectroscopy is used to study the mechanisms of exci tation and energy relaxation of charge carriers in a C60 film on a 100 -fs scale. The studies cover the laser intensity dependence of absorpt ion. The rise of absorption, peaked at zero delay times, is shown to b e replaced by electronic-vibrational relaxation with times tau1 almost -equal-to 1 ps and tau2 almost-equal-to 30 ps. Relaxation mechanisms c orresponding to these times are discussed, along with the possible rol e in kinetics of a spontaneous symmetry breaking of the excited state of C60.