Modeling ultrafast laser-driven ionization dynamics with Monte Carlo collisional particle-in-cell simulations

Ionization dynamics of cold dense matter induced by ultrashort (<100 fs) laser pulses is studied for intensities at the onset of the relativistic regime by one-dimensional kinetic simulations. As a model we use a particle-in-cell code that includes field and electron collisional ionization, as well as elastic binary Coulomb collisions. As examples for the different ionization mechanisms, we give the spatial and temporal evolution of laser-induced ionization dynamics in helium gas and solid boron targets. Special attention is paid to the quasi-static electric fields at the rear surface of laser-irradiated targets that are important for laser-ion acceleration.