Molecular dynamics simulations are used to investigate the effect of photochemical processes on molecular ejection mechanisms in laser ablation of organic solids. The presence of photochemical decomposition processes and subsequent chemical reactions changes the temporal and spatial energy deposition profile from pure photothermal ablation. A strong and broad acoustic wave propagation results and this pressure wave in conjunction with the temperature increase in the absorbing region causes the ejection of hot massive molecular clusters. These massive clusters later disintegrate in the plume into the smaller clusters and monomers due to ongoing chemical reactions. (C) 2002 Elsevier Science B.V. All rights reserved.