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R. Ross, S. Kazaoui, and N. Minami
[Trans. Mat. Res. Soc. Jnp., Vol.14B, p.1239, 1994]
The luminescence excitation and emission spectra of C60 films are presented as functions of the temperature and sample thickness. Especially for thicker films, but even for thin films, the excitation spectra deviate from the absorption spectra. The excitation spectra are compared with photoconductivity spectra of C60 films. The changes in excitation and photoconductivity spectra bear a certain resemblance. Emission and excitation spectra measured at 77K are shown in figure 1 and 2. The shapes of the emission spectra (peak position 735, 772 and 820nm) are independent of the excitation wavelength. The shape of the luminescence excitation spectra also appeared to be similar at all monitored wavelength (lambda=735, 745, 805nm). These results indicate that internal conversion takes place to the lowest states that are responsible for the luminescence emission. The excitation spectrum revealed several features of the electronic structure: the region 510-700nm is associated with intramolecular transitions; the region 510-400nm with forbidden electronic transitions but weakly allowed in solid state; the peak at 350nm corresponds to allowed transition.
