Photothermal investigation of the triplet state of carbon molecule (C60)

Photophysical properties of the triplet state of C{sub 60} (buckminsterfullerene) are investigated by photothermal techniques, thermal lens (TL), transient grating (TG), and photoacoustic (PA) methods. The quantum yield of singlet oxygen formations ({Phi}{sub {Delta}}) by the quenching of the triplet state of C{sub 60} is measured by the time-resolved TL method. The value of {Phi}{sub {Delta}} is nearly unity and independent of the excitation wavelength. The time dependence of the TL and TG signals does not show expected slow-rising components. This peculiar behavior can be explained in terms of a strong T-T absorption at the He-Ne laser wavelength. By using the PA method, the energy of the triplet state is determined to be 13,100 {plus minus} 300 cm{sup {minus}1}.