Photochemical fragmentation processes in laser ablation of organic solids

Studies on ultraviolet (UV) laser ablation of molecular solids have receive d considerable attention due to its proven and potential applications. Desp ite its active practical use the mechanisms of laser ablation are still bei ng studied and debated, One crucial mechanistic discussion is on the relati ve importance of direct photodissociation of chemical bonds versus thermal ejection following rapid conversion of light energy into heat in the ablati on processes. It is generally believed that these two processes are coupled in UV ablation resulting in difficulty in analyzing the relative importanc e of the two mechanisms. In the simulations presented here the breathing sp here model is enhanced allowing the photon absorption event to break a bond in the molecule and then have subsequent abstraction and recombination rea ctions. The initial system to model is chlorobenzene. Chlorobenzene is chos en because of simplicity of its fragmentation, entailing exclusively scissi on of the carbon-chlorine bond to yield phenyl and chlorine radicals. The r esults from the simulations allow us to study the photochemical events and their coupling with the thermal processes. (C) 2001 Elsevier Science B.V. A ll rights reserved.