Ionization in vacuum ultraviolet F2 laser ablated polymer plumes

An experimental investigation of ion generation in the 157-nm vacuum ultraviolet (VUV) F2 laser ablation of three selected polymers – glycidyl azide polymer (GAP), a triazene polymer (TP6) and polyimide – is described. An ion collector probe is used to determine the relative ion yield and white-light interferometry of ablated surfaces to ascertain mass-removal levels. The findings indicate that ions are generated under the action of the VUV laser pulse at fluences down to at least as low as the threshold for material removal. A two-photon photoionization model is proposed that provides a good description of the results.