Normal to tangential velocity conversion in cluster-surface collisions: ArN on graphite

Abstract

Collisions between large neutral argon clusters and a pyrolytic graphite surface have been investigated at normal incidence by measuring angular distributions of density and angularly resolved time-of-flight distributions of scattered species ͑essentially monomers͒. These data have been taken for two surface temperatures ͑440 and 660 K͒ with cluster sizes N ranging from 400 to 8200 atoms per cluster, and at an incoming cluster energy of 72 meV/atom. A higher incident kinetic energy ͑115 meV/atom͒ has been investigated also for Nϭ900 atoms per cluster. The experimental results have been analyzed by considering two components. First, an ''ejection'' contribution, dominant at large scattering angles, has been assigned to the evaporation of monomers from cluster material having acquired a flow velocity parallel to the surface. The average value of this flow velocity increases sharply with the incident cluster velocity in the investigated range. Second, a thermal contribution, dominant close to the surface normal, has been assigned to the trapping-desorption of monomers on the graphite surface for the smallest values of N, and to direct evaporation from the cluster when N increases.

Collision dynamics of large water clusters on graphite

“…Similar results have previously been observed for other types of weakly bound clusters, including He n , (H 2 ) n , and (N 2 ) n scattering from stainless steel, 1,2 (CO 2 ) n colliding with Cu and Si surfaces, 3 (N 2 ) n scattering from Fe and Ag surfaces, 11 and (N 2 ) n and noble gas clusters scattering from graphite. [12][13][14][15][16][17][18][19]29,31 The experimental data indicate that large water clusters are emitted from the surface by two different mechanisms, as has been reported earlier. 28 At a surface temperature of 300 K, the emission of monomers from the surface follows a cosine law dependence, which indicates that clusters that are trapped on the graphite surface lose their momentum parallel to the surface plane before being completely evaporated.…”

Cluster Impact Chemistry

“…While cluster science has grown to a well-established field during the last decades, recently a new and potentially useful area has emerged, i.e., the investigation of phenomena involving the interaction of clusters with solid surfaces. Experimental results for the scattering of atomic and molecular clusters from solid surfaces have been reported for neutral − and ionic − clusters, as well as secondary electron emission due to the impact of clusters, ,− …”

Water Cluster Collisions with Graphite Surfaces: Angular-Resolved Emission of Large Cluster Ions

“…When the collision energy is comparable to the binding energy of the cluster, the surface collision results in processes such as cluster fragmentation and scattering of surviving cluster fragments. In this energy regime collisions of van der Waals clusters with surfaces have been studied experimentally using neutral cluster beam techniques [1][2][3][4][5][6][7][8] and theoretically by molecular dynamics simulations. [9][10][11][12][13][14][15][16] The behavior of hydrogen-bonded clusters under similar conditions has also been investigated experimentally [17][18][19][20][21][22] and theoretically.…”