ON THE THRESHOLD BEHAVIOR IN LASER-ABLATION OF ORGANIC-SOLIDS

The microscopic mechanisms of the fluence threshold behavior in laser ablation of organic solids have been delineated using a breathing sphe re model and molecular dynamics simulations. Below threshold, evaporat ion is identified to occur and primarily single molecules are desorbed . Above threshold, collective ejection or ablation occurs in which lar ge molecular clusters constitute a significant portion of the ejected plume. The laser induced pressure buildup and the phase explosion due to overheating of the irradiated material are identified as the key pr ocesses that determine the dynamics of laser ablation. (C) 1997 Elsevi er Science B.V.