EVIDENCE OF THE JAHN-TELLER SPLITTING OF C-60(-) IN C-60-TETRAPHENYLPHOSPHONIUMCHLORIDE FROM AN ELECTRON-SPIN-RELAXATION STUDY

Pulsed EPR measurements of the transverse and longitudinal relaxation times of the C-60(-)-anion radical in crystalline C-60-tetraphenylphos phoniumchloride were done at temperatures from 4 to 40 K. Above 40 K t o room temperature the longitudinal relaxation time was taken from the cw-EPR linewidth. The low-temperature data are explained in terms of local magnetic fluctuations, slow C-60(-) motion, and localized two-le vel states related with the local disorder. The relaxation data at hig her temperatures reveal experimental evidence for the Jahn-Teller dist ortion of the C-60(-)-anion radical and allow to determine the Jahn-Te ller splitting between the at, electronic ground state and the excited el, state of the unpaired electron.