Interband dielectric function ofC60andM6

Ying Wang

¹

,

J. M. Holden

²

,

Apparao M. Rao

³

et al.

Fullerenes

“…179 For the case of C 60 , this value for ei(0) can be compared with the value £i(0) = 4.4 ± 0.2 obtained from capacitance measurements. 181 Fringe structure in the transmission data of C 6 o solid films has been used 67 to obtain a value ei(0) = 4.1 in better agreement with the capacitance measurements. 181 Near-normal incidence, transmission/reflection studies on Ceo and MeCeo (M = K, Rb, and Cs) 67 have been carried out in the range 0.5-6 eV to determine the optical dielectric function e(co).…”

“…181 Fringe structure in the transmission data of C 6 o solid films has been used 67 to obtain a value ei(0) = 4.1 in better agreement with the capacitance measurements. 181 Near-normal incidence, transmission/reflection studies on Ceo and MeCeo (M = K, Rb, and Cs) 67 have been carried out in the range 0.5-6 eV to determine the optical dielectric function e(co). 28 For C 60 , these studies 67 have assigned absorption structure to transitions between specific, narrow (0.3-0.5 eV) energy bands, using a band model to describe the electronic states.…”

“…Here the peak (maximum emission) is at -740 nm (-1.7 eV), and the emission spectra exhibit clear vibronic structure. 67 For C6o, the occupation of the triplet T x state has been shown to be quenched with nearly 100% efficiency by dioxygen, leading to a very short lifetime for Cgo in the excited T x state and a fast nonradiative relaxation to the ground state in the presence of oxygen. 132 ' 174 ' 176 However, in the organic glass solvent, the effect of oxygen on the triplet state lifetime is less important because of the lower oxygen diffusion and reduced collision rate.…”

Vibrational spectroscopy of C60

“…The transition energy between these two levels was placed at 2.7 eV. This is considerably lower than the value of 3.0 eV found for the lowest allowed transition in C 60 in solution [144], although it is consistent with most absorption and ellipsometric measurements on C 60 films and single crystals [147,148]. The reason for the discrepancy is now well understood in terms of the width of the electronic bands derived from the molecular orbitals.…”

“…Several strong transitions were identified in a range between 0.2 eV and 0.7 eV above the absorption threshold, which was found at 1.46 eV. When the experimental value of 1.72 eV [147,148] is used, these strongest "forbidden" transitions are predicted to occur between 1.9 eV and 2.4 eV, overlapping the energy range within which the Raman resonance was observed by Sinha et al [136] and Guha et al [138] An alternative explanation for the visible Raman resonance was proposed by Matus et al [137]. These investigators suggested an interpretation based on the "A-term" in Albrecht's molecular theory of resonance Raman scattering [149], with the resonant optical transition occurring between bands derived from the h u and t 1g molecular orbitals.…”