OBSERVATION OF TRIPLET-STATE OF CHARGE-TRANSFER EXCITONS IN C-60 THIN-FILM

We have studied formation and energy structure of tripler states of ch arge-transfer excitons in C-60 thin film by means of pump and probe sp ectroscopy in a vast time domain from 100 fs to 100 ms. In solid C-60, absorption bleaching which lasts up to several hundred milliseconds i s observed slightly below the absorption band due to charge-transfer e xcitons (CT excitons). This provides a spectroscopic evidence for exis tence of an inter-molecular tripler state due to CT excitons in solid C-60. The energy splitting between singlet and triplet CT exciton stat es is 0.09 eV, and the lifetime of triplet CT excitons is similar to 5 0 ms. (C) 1998 Elsevier Science B.V. All rights reserved.