Non-IPR C60 solids

LÖFFLER, DANIEL; BAJALES, NOELIA; CUDAJ, MARCOS; WEIS, PATRICK; LEBEDKIN, SERGEI; BIHLMEIER, ANGELA; TEW, DAVID; KLOPPER, WIM; BÖTTCHER, ARTUR; KAPPES, MANFRED

THE JOURNAL OF CHEMICAL PHYSICS

American Institute of Physics

Lugar: Melville,New York; Año: 2009 vol. 130 p. 1647051 - 16470511

0021-9606

Films comprising predominantly novel isomers of C60 [=C60 (nIPR)] have been generated by low energy ion beam deposition of vibronically excited C60+ onto graphite followed by selective sublimation of C60 (Ih) from the deposite disomer mixture. The incident ions were generated by electron impactionization/fragmentation of sublimed C70. Images of the C60 (nIPR) films obtained by applying atomic force microscopy show aggregates, which we attribute to covalently interlinked C60 (nIPR) units.The covalent bonds are inferred from the significantly higher therma stability of the C60 (nIPR) films compared to the C60(Ih)van der Waals solid–as measured by thermal desorption with mass spectrometric detection of the C60 mass channel the only desorbable species. In contrast to the characteristic doublet structure of the occupied valence band in the ultraviolet photoelectron spectrum of pure C60(Ih), the valence band of C60 (nIPR) films exhibits a triplet feature with the additional peak occurring at a binding energy of 2.6eV. This is an indicator of the electronic modifications induced by intermolecular bonding. C60 (nIPR)films exhibit a narrower band gap than found for C60 (Ih).They also have significantly different chemical reactivity toward incorporation of thermal energy deuterium atoms. In order to model the experimental photoelectron spectra, various covalently linked oligomers of C60 (C2v),the second most stable conventional 60-atom fullerene cage, were calculated by means of the density functional theory. These spectral predictions together with analogous previous observations on related fullerene solids such as C58 lead us to infer that C60 (nIPR) films consist of fullerene cage isomers containing one or more adjacent pentagon pairs, which mediate covalent cage-cage interconnection.