N2- radical anion reversibly formed at the surface of "electron-rich" alkaline-earth oxides

Elio Giamello, Maria Cristina Paganini, Mario Chiesa, Damien M. Murphy, Gianfranco Pacchioni, Raffaella Soave, A. Rockenbauer

Research output: Contribution to journalArticle

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Abstract

Physisorption of N2 gas onto the surface of a metal oxide (MgO or CaO), containing paramagnetic trapped electron centers (Fs+ 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 N2- radical anion. The species in fact contains two nitrogen atoms and its g and A tensors are in agreement with what observed for the N2- radical trapped in irradiated crystal of various azides. The surface N2- 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 N2 adlayer is desorbed, in fact, the N2- spectrum vanishes and the original Fs+ 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 π Orbitals of the admolecule.

Original languageEnglish
Pages (from-to)1889-1890
Number of pages2
JournalJournal of Physical Chemistry B
Volume104
Issue number9
Publication statusPublished - Mar 9 2000

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alkaline earth oxides
Oxides
Anions
Negative ions
Earth (planet)
anions
Paramagnetic resonance
Electrons
electron transfer
Hamiltonians
Color centers
Physisorption
electrons
Azides
color centers
nitrogen atoms
Tensors
Carrier concentration
metal oxides
Nitrogen

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

Giamello, E., Paganini, M. C., Chiesa, M., Murphy, D. M., Pacchioni, G., Soave, R., & Rockenbauer, A. (2000). N2- radical anion reversibly formed at the surface of "electron-rich" alkaline-earth oxides. Journal of Physical Chemistry B, 104(9), 1889-1890.

N2- radical anion reversibly formed at the surface of "electron-rich" alkaline-earth oxides. / Giamello, Elio; Paganini, Maria Cristina; Chiesa, Mario; Murphy, Damien M.; Pacchioni, Gianfranco; Soave, Raffaella; Rockenbauer, A.

In: Journal of Physical Chemistry B, Vol. 104, No. 9, 09.03.2000, p. 1889-1890.

Research output: Contribution to journalArticle

Giamello, E, Paganini, MC, Chiesa, M, Murphy, DM, Pacchioni, G, Soave, R & Rockenbauer, A 2000, 'N2- radical anion reversibly formed at the surface of "electron-rich" alkaline-earth oxides', Journal of Physical Chemistry B, vol. 104, no. 9, pp. 1889-1890.
Giamello E, Paganini MC, Chiesa M, Murphy DM, Pacchioni G, Soave R et al. N2- radical anion reversibly formed at the surface of "electron-rich" alkaline-earth oxides. Journal of Physical Chemistry B. 2000 Mar 9;104(9):1889-1890.
Giamello, Elio ; Paganini, Maria Cristina ; Chiesa, Mario ; Murphy, Damien M. ; Pacchioni, Gianfranco ; Soave, Raffaella ; Rockenbauer, A. / N2- radical anion reversibly formed at the surface of "electron-rich" alkaline-earth oxides. In: Journal of Physical Chemistry B. 2000 ; Vol. 104, No. 9. pp. 1889-1890.
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AU - Soave, Raffaella

AU - Rockenbauer, A.

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AB - Physisorption of N2 gas onto the surface of a metal oxide (MgO or CaO), containing paramagnetic trapped electron centers (Fs+ 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 N2- radical anion. The species in fact contains two nitrogen atoms and its g and A tensors are in agreement with what observed for the N2- radical trapped in irradiated crystal of various azides. The surface N2- 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 N2 adlayer is desorbed, in fact, the N2- spectrum vanishes and the original Fs+ 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 π Orbitals of the admolecule.

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