Unoccupied electronic states in a hexatriacontane thin film studied by inverse photoemission spectroscopy

The electronic structure of low-lying unoccupied electronic states in a hexatriacontane (n-C36H74) thin film was directly observed using inverse photoemission spectroscopy (IPES). In the IPE measurements, it was confirmed that the hexatriacontane thin film is easily degraded by electron irradiation. Therefore by reducing the current density of the incident electrons gradually we finally obtained a reliable IPE spectrum free from radiation damage and/or surface charging. As a result, we conclude the IPE spectrum reported by Dudde and Reihl was influenced by radiation damage. The reliable spectrum shows two features near the vacuum level: they were not resolved in the reported spectrum. Further, it is compared with the reported results from other electron spectroscopies and theoretical calculations concerning the unoccupied electronic states in long chain alkanes.