Photothermal deflection spectra of crystalline C60Sx and RbC60

Abstract The optical absorption spectra of C 60 , C 60 S x single crystals and polymerized crystalline RbC 60 in the weak-absorption region (from 0.6 to 2.3 eV) have been measured by photothermal deflection spectroscopy (PDS). The optical energy gaps, E opt , corresponding to optically forbidden transitions of weak absorption, were derived from Tauc plots as 1.63 and 1.72 eV for the single crystal C 60 and C 60 S x , respectively. The weak-absorption characteristics of crystalline C 60 , C 60 S x and RbC 60 are discussed. With respect to pristine C 60 , the absorption edge of the single crystal of C 60 S x shows a blue shift of about 0.1 eV, indicating that C 60 is electronically isolated in this compound. The absorption edge of polymerized RbC 60 crystal, however, red-shift significantly in PDS, implying that there is electronic interaction between the host C 60 molecules and the guest Rb atoms.