Eur. Phys. J. D 16, 365–368 (2001) T HE EUROPEAN P HYSICAL JOURNAL D c  EDP Sciences Societ` a Italiana di Fisica Springer-Verlag 2001 Molecular beam deflection experiments on mixed clusters Permanent dipole of transition metal-C 60 compounds I. Compagnon, R. Antoine, D. Rayane, Ph. Dugourd a , and M. Broyer Laboratoire de Spectrom´ etrie Ionique et Mol´ eculaire b , Universit´ e Lyon I et CNRS, 43 boulevard du 11 novembre 1918, 69622 Villeurbanne Cedex, France Received 22 November 2000 Abstract. Gas phase Ti-C60 clusters are studied by molecular beam electric deflection. The permanent dipole moment of the TiC60 molecule is determined. It is equal to 8.1 ± 1.5 D. This dipole is due to a transfer of electron from the transition metal atom to the C60 cage. No dipole is observed for Ti(C60 )2 molecules. This is in agreement with the symmetrical dumbbell-like structure that has been previously proposed. PACS. 33.15.Kr Electric and magnetic moments (and derivatives), polarizability, and magnetic susceptibility – 36.40.Cg Electronic and magnetic properties of clusters – 61.48.+c Fullerenes and fullerene-related materials 1 Introduction Since the discovery of C 60 , a versatile derivatization chem- istry of fullerenes has been developed [1]. Transition metal- fullerene complexes have attracted much fascination due to their potentiality for catalytic activity and the possibil- ity of forming new supermolecular compounds. Mass spec- trometry studies have shown that transition metal-C 60 complexes can be produced in the gas phase [2–4]. Laser- induced transformations from transition metal fullerenes to metal-carbide and met-car compounds have been evi- denced by Martin and coll. [5]. Kaya and coll. have used absorption reactivity in a conventional flow-tube reactor to obtain information on the structure of these clusters. The reactivity of Ti n (C 60 ) n+1 clusters toward O 2 and CO is in favor of a multiple dumbbell structure, in which tran- sition metal atoms and C 60 are alternatively stacked [6,7]. In this article, we report the first measurement of the per- manent dipole of transition metal-C 60 compounds. The results obtained by the molecular beam deflection tech- nique give new information on the electronic and geomet- ric structures of small titanium fullerene clusters. 2 Experimental set up Figure 1 shows a schematic of our experimental set up. It consists of a laser vaporization source, an electric de- flector, and a position sensitive time of flight mass spec- trometer. Titanium-C 60 clusters are generated in a laser a e-mail: dugourd@lasim.univ-lyon1.fr b UMR 5579 du CNRS Fig. 1. Schematic of the experimental set up. vaporization source with two rods and two pulsed lasers. We use the third harmonic of a Nd:YAG to desorb a C 60 rod (> 99.9% purchased from MER corp.). A low laser power is used in order to avoid any fragmentation of the fullerenes. The second harmonic of a Nd:YAG is focused on a titanium rod. This laser is fired with a time delay of a few microseconds after the first laser pulse. The time delays of both lasers are synchronized on a piezo-electric pulsed valve. Helium is used as carrier gas. The clusters leave the source through a 5 cm long nozzle which can be cooled down to 85 K. The molecular beam is skimmed and tightly collimated by two slits. It is deflected with a “two-wire” electric field configuration. The clusters are ionized 1 m after the deflector in the extraction region