Ion energy enhancement in laser-generated plasma of metallic-doped polymers

Laser-generated plasma in vacuum are obtained ablating hydrogenated polymers at the Physics Department of Messina University and Prague Asterix Laser System laboratory of Prague. In the first case, a 3-ns, 532-nm Nd:Yag laser at 5 x 10(9) W/cm(2) intensity was employed. In the second case, a 300-ps, 438-nm iodine laser at 5 x 10(14) W/cm(2) intensity was employed. Different ion collectors are used in time-of-flight configuration to monitor 'on line' the ejected ions from the plasma at different angles with respect to the normal direction to the target surface. Measurements demonstrated that the mean ion velocity, directed orthogonally to the target, increases for ablation of polymers doped with metallic elements (Br, Cu, Au and W) with respect to that obtained with no-doped polymers. The possible mechanism explaining the results can be found in the different electron density of the plasma, due to the higher number of electrons coming from the metallic doping elements. This charge enhancement increases the equivalent ion voltage acceleration, i.e. the electric field generated in the non-equilibrium plasma placed in front of the ablated target surface.