title: Nature of the chemical bond between metal atoms and oxide surfaces: new evidences from spin density studies of K atoms on alkaline earth oxides.
abstract: We have studied the interaction of K atoms with the surface of polycrystalline alkaline-earth metal oxides (MgO, CaO, SrO) by means of CW- and Pulsed-EPR, UV-Vis-NIR spectroscopies and DFT cluster model calculations. The K adsorption site is proposed to be an anionic reverse corner formed at the intersection of two steps, where K binds by more than 1 eV, resulting in thermally stable species up to about 400 K. The bonding has small covalent and large polarization contributions, and the K atom remains neutral, with one unpaired electron in the valence shell. The interaction results in strong modifications of the K electronic wave function which are directly reflected by the hyperfine coupling constant, (K)a(iso). This is found to be a very efficient "probe" to measure the degree of metal-oxide interaction which directly depends on the substrate basicity. These results provide an original and general model of the early stages of the metal-support interaction in the case of ionic oxides.
authors.affiliation: Dipartimento di Chimica IFM, Università di Torino, Italy. m.chiesa@unito.it
authors.forename: Mario
authors.initials: M
authors.lastname: Chiesa
authors.forename: Elio
authors.initials: E
authors.lastname: Giamello
authors.forename: Cristiana
authors.initials: C
authors.lastname: Di Valentin
authors.forename: Gianfranco
authors.initials: G
authors.lastname: Pacchioni
authors.forename: Zbigniew
authors.initials: Z
authors.lastname: Sojka
authors.forename: Sabine
authors.initials: S
authors.lastname: Van Doorslaer