Reactive scattering of clusters and cluster ions from solid surfaces

Abstract

Specific chemical reactions take place in a cluster when it impinges on a solid surface. These intracluster processes ranging from vibrational excitation to atomic rearrangements are called 'cluster-impact' processes, the features of which change specifically with the collision energy and the cluster size. The specificity of the cluster-impact processes arises from impulsive energy transmission to specific modes of the cluster followed by rapid energy redistribution among other degrees of freedom, including those of the surface. In this review, citing several representative collision systems (cluster + surface), we explain the features of a cluster-impact process by dividing the collision energy into several energy ranges, in each of which a characteristic feature is manifested; high vibrational excitation of fullerenes in the lowest energy range, mechanical bond splitting of I − 2 and a four-centre reaction between N 2 and O 2 in a higher energy range, etc.

Experimental observation of two-dimensional charge polarization in unisized platinum cluster disk bonded to silicon(1 1 1) surface

“…Platinum cluster cations, Pt þ n , were produced in a gas-aggregation chamber equipped with a magnetron sputtering source [36] and size-selected in a quadrupole mass-filter; the current and the size of Pt þ n were typically ranged in 900-50 pA and 5-45, respectively. The unisized Pt þ 30 were allowed to collide onto a Si(1 1 1)-7 Â 7 surface (so-called cluster impact [37]) maintained at 300 K at the collision energy of 1.3 ± 0.2 eV per platinum atom and at an ambient pressure below 6 Â 10 À8 Pa; 10 nC of Pt þ 30 was irradiated to a circular region of $3 mm in diameter on the sample surface. Undesired neutral impurities were removed from the Pt þ 30 beam by deflecting the beam off the original beam axis by 7 mm in front of the sample.…”

Chemical Behavior Under Extreme Conditions

“…Experiments at the Cluster Research Laboratory of the Toyota Technological Institute and elsewhere have explored this novel regime of dynamics where the duration of collisions within the cluster is so short. Reviews of experimental [1] and theoretical [2] work are available.…”

Surface collisions of small cluster ions at incident energies 10–102eV

“…Monomer evaporation in ion cluster fragmentation, following deposition of low energies in them, has been usually described in terms of the evaporative ensemble model [2,26,27]. In surface collisions, the phenomenon was studied in detail in scattering of neutral atomic and molecular clusters and described in terms of the thermokinetic model [5,28]. This type of fragmentation is connected with a rather large mean lifetime of the energized species (order of hundreds of ps) and energy redistribution throughout the system before it starts to dissociate.…”