Physisorption of N-2 gas onto the surface of a metal oxide (MgO or CaO), containing paramagnetic trapped electron centers (F-s(+) color centers), leads to the formation of a paramagnetic species that, on the basis of its EPR spectrum and of the related spin-Hamiltonian parameters, is identified as a N-2(-) radical anion. The species in fact contains two nitrogen atoms and its g and A tensors are in agreement with what observed for the N-2(-) radical trapped in irradiated crystal of various azides. The surface N-2 species is formed by surface-to-molecule one-electron transfer, and its stability strictly parallels the stability of the physisorbed layer, the species formation being completely reversible and pressure dependent. When the N-2 adlayer is desorbed, in fact, the N-2(-) spectrum vanishes and the original F-s(+) spectrum is restored. Ab initio quantum chemical calculations on an embedded MgO cluster fully confirm the observed phenomenon indicating, in agreement with EPR analysis, the electron transfer of a large fraction of electron density into the pi orbitals of the admolecule.

Giamello, E., Paganini, M., Chiesa, M., Murphy, D., Pacchioni, G., Soave, R., et al. (2000). N-2(-) radical anion reversibly formed at the surface of "electron-rich" alkaline-earth oxides. JOURNAL OF PHYSICAL CHEMISTRY. B, CONDENSED MATTER, MATERIALS, SURFACES, INTERFACES & BIOPHYSICAL, 104(9), 1887-1890 [10.1021/jp994126y].

N-2(-) radical anion reversibly formed at the surface of "electron-rich" alkaline-earth oxides

PACCHIONI, GIANFRANCO;
2000-03-09

Abstract

Physisorption of N-2 gas onto the surface of a metal oxide (MgO or CaO), containing paramagnetic trapped electron centers (F-s(+) color centers), leads to the formation of a paramagnetic species that, on the basis of its EPR spectrum and of the related spin-Hamiltonian parameters, is identified as a N-2(-) radical anion. The species in fact contains two nitrogen atoms and its g and A tensors are in agreement with what observed for the N-2(-) radical trapped in irradiated crystal of various azides. The surface N-2 species is formed by surface-to-molecule one-electron transfer, and its stability strictly parallels the stability of the physisorbed layer, the species formation being completely reversible and pressure dependent. When the N-2 adlayer is desorbed, in fact, the N-2(-) spectrum vanishes and the original F-s(+) spectrum is restored. Ab initio quantum chemical calculations on an embedded MgO cluster fully confirm the observed phenomenon indicating, in agreement with EPR analysis, the electron transfer of a large fraction of electron density into the pi orbitals of the admolecule.
Articolo in rivista - Articolo scientifico
chemisorption, EPR, DFT calculations
English
1887
1890
Giamello, E., Paganini, M., Chiesa, M., Murphy, D., Pacchioni, G., Soave, R., et al. (2000). N-2(-) radical anion reversibly formed at the surface of "electron-rich" alkaline-earth oxides. JOURNAL OF PHYSICAL CHEMISTRY. B, CONDENSED MATTER, MATERIALS, SURFACES, INTERFACES & BIOPHYSICAL, 104(9), 1887-1890 [10.1021/jp994126y].
Giamello, E; Paganini, M; Chiesa, M; Murphy, D; Pacchioni, G; Soave, R; Rockenbauer, A
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/10281/23790
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