Revisit of recombination processes of low-charge-state ion generation during picosecond intense laser-gas interaction

Abstract

The origin of He + ions in picosecond intense laser-gas interaction was experimentally and numerically investigated. A nanosecond laser pulse was used to modulate the plasma condition, which helps to distinguish the origin of the helium ions with different charge states. By comparing the energy spectra of He 2 + and He + ions in the experiments with/without plasma shaping, we found neither ion-atom nor electron-ion recombination is responsible for the He + generation, which is supported by two-dimensional hydrodynamic simulations and theoretical calculations.