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In experiments on electronic properties of the $C_{60}F_{46}$ and LiF cluster, $C_{60}F_{46}$ molecule has been studied through depositing Fe and Pd thin films on the substrates first, then $C_{60}F_{46}$ on the thin films, or through the inverse prosess. By measuring the core electron spectra, valence band spectra, constant final state spectra and energy distribution curves, chemical reactive mechanisms of the $C_{60}F_{46}$ on different substrates were studied. The reaction between $C_{60}F_{46}$ and Fe thin film indicates that $C_{60}F_{46}$ is a strongly active reagent. Both valence band and C 1s core shell spectra show the formation of C#-[60], Fe$F_{2}$ and Fe$F_{3}$. When the deposition process is inversed, i.e., the Fe is deposited onto the $C_{60}F_{46}$_ film, the 3p level of the Fe appears in four distinct peaks, among which three have been attributed to the atomic free Fe, $Fe^{2+}$ and $Fe^{3}$ ions, respectively. The fourth have been attributed to incorporation of Fe atom in the $C_{60}$ ball by formation of coordinate bonds between non-bonded $\pi$ electrons of $C_{60}$ and unfilled antibonding d orbitals. There exist considerable circumstantial evidences to prove that this peak is due to the Fe inside the $C_{60}$ ball rather than on the surface of $C_{60}$. The reaction between Pd and $C_{60}F_{46}$_ is not so strong as with Fe, but still exists somewhat weak interaction between them. In the points of size, clusters are found between atom, molecule and condensed matter. The experiments on LiF cluster indicate that the dimension of the cluster has decisive effect on its electronic structure, and the binding energy of F 1s core level increases as the size of FLi cluster reduces.
In the surface physics research, some new progresses were made in experiments employing angular resolved photoemission technique. A new surface state on Cu(111) surface was revealed at 2.9eV below Fermi level near K point of surface Brillion Zone which belongs to d-electron Tamm type. The valence band interaction between Co and Cu(111) has been studied, suggesting that interdiffussion occurs between Cu and submonolayer Co grown on Cu(111) surface by molecular beam epitaxy, electron transfer from Co to Cu resulting in the s-d band of Cu moving to high binding energy, giving an answer to the problem why no AF and GM effect was detected on Co/Cu(111) multilayer.
Good results were also got in the project of adsorption of metal surface and metal-metal interface.
Yang Yi and Liu Fengqin --------------------------------------------------------------------- [ Table of contents | Next Page | Previous Page ]
June 1995 BEPC News