Laser-induced modification of the size distribution of nanoparticles produced during ultrashort laser ablation of solid targets in vacuum

We demonstrate that the average size and the size distribution of nanoparticles produced by ultrashort laser ablation in vacuum can be modified by irradiation of the nanoparticles' plume during its vacuum expansion with a nanosecond, UV laser pulse. The experimental results are interpreted by means of a simple analytical model of the laser-particle interaction, heating and vaporization. This technique thus shows to be a simple and general way to control, in vacuum, the average size and distribution of nanoparticles of different elements.