Driving high threshold chemical reactions during the compression interlude in cluster surface impact

Molecular-dynamics simulations of a cluster impacting a hard surface show that, initially, the cluster is rapidly compressed and translationally heated. During this short but distinct stage, the cluster is a suitable medium for chemistry: the number of layers of the cluster is not changing; the constituents of the cluster can collide several times and both bimolecular and collisionally driven unimolecular reactions can occur. Hypersonic velocities of impact are needed for a considerable temperature rise. Following compression, the cluster fragments by expanding into a hemispheroidal plume. For supersonic impact, the cluster expands nearer to the surface forming an oblate, omelet-like, hemispheroid.