The velocity and angular distributions of the positively charged, negatively charged and neutral products from 308 nm laser ablation of polyimide have been investigated. The differences in the distributions for the three kinds of products can be attributed to the different formation mechanisms. Positive ions are formed in the centre of the laser focus and are ejected with a cos4θ distribution about the surface normal. Neutral and negatively charged products show a cos θ angular distribution. All products are ejected with supersonic velocities with vpositive>vnegative>vneutral for a given laser fluence.
Bibliographical noteFunding Information:
The authors would like to thank Professor I.V. Hertel for his interest in the present work. Financial support by the Bundesministerium fur Forschung und Technologie (BMFT) under contract number 13N5628 “Materialbearbeitung mit Excimerlasern” is gratefully acknowledged.