C-58 on HOPG: Soft-landing adsorption and thermal desorption

Electron-impact induced dissociation/ionization of C-60 molecules was used to produce an intense beam of C-58(+) ions. This was directed towards a HOPG (highly oriented pyrolytic graphite) substrate under nominally perpendicular impact conditions in order to generate deposits by soft-landing (kinetic energy <0.1 eV atom(-1)). Deposited C-58 molecules could subsequently be thermally desorbed intactly. Thermal desorption mass spectra of the deposits exhibit only C-58. Surface deposited C-58 can react with background gases to generate hydride derivatives C58Hn which are also desorbable. The apparent desorption energy of C-58 and C58Hn molecules from the HOPG surface varies with increasing adsorbate coverage from 2 +/- 0.1 to 2.2 +/- 0.1 eV as determined by a Redhead analysis. These values are 0.7 +/- 0.1 eV larger than found for C-60 desorbed from the same substrate.