The vibrational spectroscopy of the electronically closed-shell (Al2O3)(n)(AlO)(+) cations with n = 1-4 is studied in the 530-1200 cm(-1) range by infrared predissociation spectroscopy of the corresponding ion-He atom complexes in combination with quantum chemical calculations. In all cases we find, assisted by a genetic algorithm, global minimum structures that differ considerably from those derived from known modifications of bulk alumina. The n = 1 and n = 4 clusters exhibit an exceptionally stable conical structure of C-3v symmetry, whereas for n = 2 and n = 3, multiple isomers of lower symmetry and similar energy may contribute to the recorded spectra. A blue shift of the highest energy absorption band is observed with increasing cluster size and attributed to a shortening of Al-O bonds in the larger clusters. This intense band is assigned to vibrational modes localized on the rim of the conical structures for n = 1 and n = 4 and may aid in identifying similar, highly symmetric structures in larger ions.

Identification of Conical Structures in Small Aluminum Oxide Clusters: Infrared Spectroscopy of (Al2O3)(1-4)(AlO)(+) / Santambrogio, Gabriele; Janssens, E; Li, Sh; Siebert, T; Meijer, G; Asmis, Kr; Dobler, J; Sierka, M; Sauer, J.. - In: JOURNAL OF THE AMERICAN CHEMICAL SOCIETY. - ISSN 0002-7863. - 130:45(2008), pp. 15143-15149. [10.1021/ja805216e]

Identification of Conical Structures in Small Aluminum Oxide Clusters: Infrared Spectroscopy of (Al2O3)(1-4)(AlO)(+)

SANTAMBROGIO, GABRIELE;
2008

Abstract

The vibrational spectroscopy of the electronically closed-shell (Al2O3)(n)(AlO)(+) cations with n = 1-4 is studied in the 530-1200 cm(-1) range by infrared predissociation spectroscopy of the corresponding ion-He atom complexes in combination with quantum chemical calculations. In all cases we find, assisted by a genetic algorithm, global minimum structures that differ considerably from those derived from known modifications of bulk alumina. The n = 1 and n = 4 clusters exhibit an exceptionally stable conical structure of C-3v symmetry, whereas for n = 2 and n = 3, multiple isomers of lower symmetry and similar energy may contribute to the recorded spectra. A blue shift of the highest energy absorption band is observed with increasing cluster size and attributed to a shortening of Al-O bonds in the larger clusters. This intense band is assigned to vibrational modes localized on the rim of the conical structures for n = 1 and n = 4 and may aid in identifying similar, highly symmetric structures in larger ions.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11696/28924
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