title: The LUMO-derived band of the [Formula: see text] phases.
abstract: The LUMO-derived band of the [Formula: see text] compound was investigated by means of x-ray and UV photoemission and photoelectric yield spectroscopies. A double-peak structure is found, with peak maxima at 1.1 eV and 0.35 eV. The relative magnitude of the two peaks is strongly temperature dependent: a large transfer of spectral weight from the lower- to the higher-binding-energy peak takes place upon cooling to 110 K. The peaks are tentatively attributed to the dimer and the polymeric phase respectively. However the behaviour as a function of temperature does not agree with the metastability of the dimer phase at room temperature. The position of the Fermi level is compatible with a correlated system on the border of the metal - insulating transition.
authors.affiliation: Dipartimento di Fisica `E Amaldi', Universitá di Roma III via Vasca Navale 84, 00146 Rome, Italy, and Istituto Nazionale di Fisica della Materia, Unitá di Roma III, via Vasca Navale 84, 00146 Rome, Italy.
authors.forename: M
authors.initials: M
authors.lastname: De Seta
authors.forename: L
authors.initials: L
authors.lastname: Petaccia
authors.forename: F
authors.initials: F
authors.lastname: Evangelisti