Dissociation dynamics of diatomic molecules embedded in impact heated rare gas clusters

Abstract

Emission spectra of homonuclear diatomic rare gas molecules in solid neon Molecular dynamics simulations demonstrate facile dissociation of halogen molecules embedded in rare gas clusters upon impact at a surface at collision velocities up to 10 kmls. Two pathways are discerned: a heterogeneous dissociation of the molecule on the surface and a homogeneous mechanism where rare gas atoms which have rebounded from the surface cause the translationalvibrational coupling. The total yield of dissociation of the clustered molecule can reach up to 100%, whereas the yield of dissociation of the bare, vibrationally cold molecule saturates below 40%. A systematic study of the role of different conditions is made possible by not accounting for the atomic structure of the surface. The role of dissipation at the surface is found, however, to be quite important and is allowed for. Larger clusters, clusters of the heavier rare gases and a more rigid surface, all favor the homogeneous mechanism. Evidence for a shock front which, upon the initial impact, propagates into the cluster; the binary nature of the homogeneous dissociation process; and the absence of a dominant cage effect are discussed. A quantitative functional form of the velocity dependence of the yield of dissociation, which accounts for the size of the cluster, the rigidity of the surface and other attributes, is used to represent the data. The physics of the processes within the cluster is dominated by the novel dynamical features made possible when the duration of the atom-molecule collisions is short compared to the vibrational period. This "sudden" regime is sudden with respect to all modes of the nuclear motion and provides a hitherto unavailable tool for examination of reaction dynamics under extreme conditions. 8606

Ionization of water clusters by collisions with graphite surfaces

“…The appearance of a peak close to the tangential direction has been shown for other systems to be due to the survival of large cluster fragments [12][13][14]. In related work, surface scattering of clusters with impact velocities of 1-10 km/s has been shown to result in microshock wave propagation in the cluster which may induce intracluster reactions [15][16][17].…”

Low energy acetone dimer ion/surface collisions studied with high energy resolution

“…In particular, we have been able -as predicted by Cleveland and Landman [14] (see also [15,[36][37][38][39]) using molecular-dynamics simulations -to observe here besides surface induced dissociation (SID) also surface induced reactions (SIR) of acetone dimer ions upon impact on a hydrocarbon covered stainless steel surface. Using fully deuterated acetone dimer ions we obtained evidence for the occurrence of two competing surface-induced reactions, i.e., on the one hand intra-cluster ion molecule reactions leading to the production of the deuteronated acetone monomer ion (CD 3 COCD 3 )D + and on the other hand hydrogen pick-up reactions leading to the formation of the protonated acetone monomer ion (CD 3 COCD 3 )H + .…”

The entropy of a single large finite system undergoing both heat and work transfer

“…with the surface. In larger clusters where the ratio of front end to all atoms is even lower this scenario causes a periodic shock wave to propagate within the cluster [21,31]. Eventually the cluster begins to spread out.…”