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Issue A&A
Volume 420, Number 2, June III 2004
Page(s) 547 - 552
Section Interstellar and circumstellar matter
DOI http://dx.doi.org/10.1051/0004-6361:20034117



A&A 420, 547-552 (2004)
DOI: 10.1051/0004-6361:20034117

Experimental study of gas phase titanium and aluminum oxide clusters

K. Demyk1, 2, D. van Heijnsbergen1, G. von Helden1 and G. Meijer1, 3, 4

1  FOM-Institute for Plasmaphysics Rijnhuizen, Edisonbaan 14, 3439MN Nieuwegein, The Netherlands
2  Present address: PhLAM, Université des Sciences et Technologies de Lille, 59655 Villeneuve d'Ascq Cedex, France
3  Dept. of Molecular and Laser Physics, University of Nijmegen, Toermooiveld 1, 6525 Nijmegen, The Netherlands
4  Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany

(Received 24 July 2003 / Accepted 23 February 2004)

Abstract
We present an experimental study of the vibrational properties of gas phase titanium oxide and aluminum oxide clusters. The titanium and aluminum oxide clusters have a stoichiometry of (Ti 2O 3) x-(TiO 2) y (with ( x, y) from (2, 4) to (11, 29)) and AlO-(Al 2O 3) n (5  $\le$ n  $\le$ 70). The vibrational properties of the clusters are obtained using infrared resonance enhanced multi-photon ionization (IR-REMPI) spectroscopy. Titanium oxide clusters have a strong vibrational band at ~13.5  $\mu$m, suggesting that their structure is close to the rutile bulk phase of TiO 2. Aluminum oxide clusters seem to have a structure comparable to the bulk $\gamma$-Al 2O 3; their IR-REMPI spectra exhibit a vibrational band at ~11  $\mu$m and another band at ~15  $\mu$m which appears in the spectra of clusters containing more than 7-8 Al atoms and becomes more intense as the cluster size increases. As hot neutral clusters are observed to evaporate more easily electrons than neutral fragments, one can conclude that they are very stable and thus very good nucleation seeds for dust growth.


Key words: methods: laboratory -- ISM: dust, extinction

Offprint request: K. Demyk, karine.demyk@univ-lille1.fr




© ESO 2004


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