Characteristic photoelectron spectra and angular distributions of single and double ionization

Using a semiclassical rescattering model, we have investigated the photoelectron spectra and angular distributions of the single and double ionization of helium in an intense ultrashort laser pulse. Through analyzing the spectrum structure we find that the photoelectrons emitted via double ionization are hotter than that via single ionization. Our calculations also reveal a significant correlation in the angular distributions of the two photoelectrons. These results have been compared with recent experiments.