Electron-energy-loss spectroscopy of oxygen-containing fullerite films

Identically prepared fullerite films were exposed to different oxygen environments, including supersonic atomic and molecular beams as well as ambient pressure. Only in atomic oxygen does mass loss occur, likely due to fragmentation of the ${\mathrm{C}}_{60}$ cage by extraction of ${\mathrm{C}}_2$O or CO. In other cases, an epoxide overlayer is formed, involving up to five oxygen atoms interacting with the π electrons of a single cage. Electron-energy-loss spectra of the oxygenated films are compared with in situ UHV-deposited fullerite. The marked difference in the spectra is used to isolate the loss spectrum of the 18-eV plasmon of fullerine epoxide, and a Kramers-Kronig analysis of the loss function is used to estimate the epoxide band gap to be 5.5±0.5 eV.