Fragmentation of lead cluster ions (Pb N +: N = 2–20) in low-energy collisions with a highly oriented pyrolytic graphite surface has been investigated by means of a tandem time-of-flight mass spectrometer. At low incident energies, all clusters fragment dominantly by an atom loss process. This behavior is characteristic for clusters of metallic elements, but in contrast to Si N +, Ge N + and Sn N + clusters. The results therefore demonstrate differences in the electronic and geometric structure between lead clusters and the lighter group-14 element clusters. The low energy dissociation patterns were compared successfully with a recent theoretical study on lead cluster fragmentation, supporting the idea, that lead clusters cations already show signatures of metallic behavior unlike Si N +, Ge N + and Sn N + clusters of the same size.

The fragmentation behavior of the bimetallic cluster ions Sn N Pb + and Pb N Sn + has been investigated by tandem time-of-flight mass spectrometry in combination with density-functional theory. The low-energy surface-induced dissociation patterns of Sn N Pb + and Pb N Sn + with N =6-11 are dominated by the subsequent loss of atoms. For Sn N Pb + first the single lead atom is split off; in contrast the Pb N Sn + clusters dissociate mainly in fragments retaining the single tin atom, which is in full accordance with the quantum chemical results. For larger collision energies the complete set of smaller tin fragment ions Sn N−M + with M Ͻ N is found for Sn N Pb + , whereas the Pb N Sn + clusters decay into two series of Pb N−M Sn + and Pb N−MIn recent decades the properties of clusters became an interesting field of research because clusters allow someone to study the stepwise development of matter from the atom to the bulk. The structural and electronic properties of the group-14 clusters are of particular interest 1-6 because these systems permit someone to study whether the transition from covalent to metallic bonding, which takes place within this group in the bulk, manifests also in reduced dimensions. Additionally the potential of these clusters for applications in nanotechnology is particularly promising. However, not only are the pure element clusters are of interest but also doped or bimetallic cluster species 7-13 because the chemical and physical properties of doped or alloyed clusters may be tuned by varying the composition and the atomic ordering as well as the size of the clusters.For tin-lead nanoalloys it has been, for example, found that the solubility and the thermal-expansion coefficient depend sensitively on particle size. 14 This behavior has been attributed to a size-dependent cohesive energy. In order to better understand the influence of dopant atoms on the energetics of nanoalloys, we have investigated single-doped tin and lead clusters. In the present paper the surface-induced dissociation of tin-rich Sn N Pb + and lead-rich Pb N Sn + clusters with N =6-11 is analyzed to study the fragmentation behavior of the doped clusters because the unimolecular dissociation of clusters is very sensitive to the binding energies. 15 The comparison of the experimental results with quantum chemical calculations gives deeper insight into the energetics of the single-doped group-14 clusters. After a presentation of the experimental procedure, the results of our quantum chemical calculations will be discussed, followed by a detailed analysis of the experimental data in comparison with the theoretical predictions.An overview of the apparatus used for the present experiments is already reported in the literature. 16 Therefore, the experiment will be described only briefly.Bimetallic clusters are produced by a dual laser vaporization cluster source. The cluster source consists of two separate formation zones where homoatomic clusters are generated. These clusters were then transported with the carrier gas to a re...

A molecular beam apparatus has been developed for deposition and scattering experiments of size-selected clusters. The new setup combines a bimetallic laser ablation cluster source with a collinear time-of-flight mass spectrometer. Mass selection is achieved with a pulsed electrostatic mirror. A significantly improved transmission in combination with a reduction of the kinetic energy distribution of the mass selected clusters has been obtained. Without further modification of the apparatus, surface-induced dissociation of mass selected tin clusters has been investigated, demonstrating the possibility to combine cluster beam deposition and scattering experiments.

SummaryMass-selected, ligand-free FeN clusters with N = 10–30 atoms (cluster diameter: 0.6–0.9 nm) were implanted into [Al@SiOx] surfaces at a low surface coverage corresponding to a few thousandths up to a few hundredths of a monolayer in order to avoid initial cluster agglomeration. These studies are aimed towards gaining an insight into the lower limit of the size regime of carbon nanotube (CNT) growth by employing size-selected sub-nm iron clusters as catalyst or precatalyst precursors for CNT growth. Agglomeration of sub-nm iron clusters to iron nanoparticles with a median size range between three and six nanometres and the CNT formation hence can be observed at CVD growth temperatures of 750 °C. Below 600 °C, no CNT growth is observed.