Formation of solitary microstructure and ablation into transparent dielectric by a subnanosecond laser pulse (1811.11990v1)

Abstract: Laser ablation in liquid (LAL) is important technique used for formation of nanoparticles (NP). The LAL processes cover logarithmically wide range of spatiotemporal scales and is not fully understood. The NP produced by LAL are rather expensive, thus optimization of involved processes is valuable. As the first step to such optimizations more deep understanding is necessary. We employ physical models and computer simulations by thermodynamic, hydrodynamic, and molecular dynamics codes in this direction. Absorbing light metal expanding into transparent solid or liquid dielectrics is considered. We analyze an interplay between diffusion, hydrodynamic instability, and decrease of surface tension down to zero value caused by strong heating and compression transferring matter into state of overcritical fluids. The primary NPs appear during expansion and cooling of diffusion zone when pressure in this zone drops below critical pressure for a metal. Long evolution from the overcritical states to states below a critical point for a metal and down to critical point of liquid and deeply down to surrounding pressure of 1 bar is followed. Conductive heating of liquid from hot metal is significant.