Collision dynamics of large water clusters

Abstract

Classical trajectory calculations of (H2O)n+(H2O)n collisions are carried out for n=125 and n=1000. We investigate energy redistribution and fragmentation behavior for relative collision velocities up to 3000 ms−1, impact parameters up to 4 nm, and initial cluster temperatures of 160 and 300 K. Three main scattering channels are identified; coalescence, stretching separation, and shattering collisions. For small impact parameters, low collision velocities produce coalesced clusters while high velocities yield shattering behavior. Large impact parameters combined with high velocities result in stretching separation collisions. A decreased internal temperature influences the dynamics by increasing the stability of the collision complex. The results for (H2O)125 and (H2O)1000 are comparable, although the smaller size allows individual molecules to have a larger influence on the overall behavior. We find good agreement between the cluster simulations and experimental data for water drops in the micrometer range concerning the transition between coalescence and stretching separation, which shows that the clusters in some respects resemble “macroscopic” objects.