Recombination effects in laser-driven acceleration of heavy ions

Recombination effects are shown to modify the charge-state distribution achieved in the acceleration of heavy ions during high-intensity laser-solid interactions. A recombination package has been developed for particle-in-cell codes, which includes dielectronic, radiative, and three-body recombination. One-dimensional simulations were then performed to model a recent experiment, where 4.1×10^{20}Wcm^{-2} laser pulses heated thin gold targets to produce gold ion beams. Simulations show that the ion beams from 100-nm targets were unaffected by recombination, but that recombination caused charge states to drop in 300-nm targets, similar to experimental observations. These differences were attributed to target temperature, as 300-nm targets were heated to lower temperatures than 100-nm targets during the laser-target interaction, causing ions to spend more time in environments where recombination rates dominated ionization rates.