On the role of the ablated mass on the propagation of a laser-generated plasma in an ambient gas

We investigate the influence of the ablated mass on the dynamics of a laser-generated plasma expanding in an ambient gas. A laser-generated silver plasma expanding in argon was analysed by fast photo imaging. While keeping all relevant experimental parameters fixed, we changed the ablated mass per pulse, by changing the laser spot area at the target surface. We show that at fixed laser fluence, plasma dynamics undergoes dramatic changes as a function of the ablated mass per pulse. Plasma expansion dynamics is studied using drag, v(2)-drag, mixed propagation and Predtechensky-Mayorov models. Results show that, at a given laser fluence, when a shock wave forms, plasma dynamics is unequivocally determined by the ratio between the ablated mass per pulse and the gas density. Such a dynamics critically affects the kinetic energy at landing and the nanostructure resulting upon mutual assembling on the substrate of the deposited nanoparticles. Thus both the ablated mass per pulse and the laser fluence are to be known to control the nanostructure formation. Copyright (C) EPLA, 2015