Optical absorption of gas phase C60 and C70

We have measured optical absorption spectra of gas phase C60 and C70 from 1.9 to 6.5 eV at various temperatures up to 1000 K. The optical density spectra of C60 and C70 have only three and six peaks, respectively, in the measured spectrum range and can be reconstructed successfully with the same number of Lorentz oscillators. This simple spectrum structure suggests a simple view for the electronic state of a C60 molecule. We have estimated sublimation heats of C60 and C70 at 1.7 and 1.3 eV, respectively, from changes of absorption intensities with temperature.