Absorption spectra of metallofullerenes M@C82 of lanthanoids

UV/vis/NIR spectra of 10 kinds of M@C-82 (M = La, Ce, Pr, Nd, Gd, Tb, by, Ho, Er and Lu) dissolved in toluene were observed and the molar absorption coefficients were determined for each absorption peak. The absorption peak wavelengths were similar among 10 kinds of species and their averages were (630 +/- 3), (986 +/- 26), and (1406 +/- 5) nm. The molar absorption coefficients for the peaks around 630 and 1406 nm were found similar for all the species although those for the peak at 986 nm showed a wider variation among the ten. Oscillator strengths have been derived from the observed data. Those for the 630 nm absorption are in the range of 0.05-0.1 which reveals that the transition is allowed, and they slightly decrease as the atomic number of the encapsulated atom is increased. The oscillator strengths for the 986 and 1406 nm absorption are, however, about 1 order of magnitude smaller, and those for the 986 nm absorption vary appreciably as the degree of filling of the 4f orbital changes.