Multiphoton double ionization of helium using femtosecond laser pulses

Abstract

A time-dependent close-coupling method is used to calculate the multiphoton double ionization of He using femtosecond laser pulses. Total double ionization probabilities are calculated for 2, 3, 4, and 5 photon absorption in the photon energy range from 10 to 60 eV. Single and triple differential probabilities are calculated for 2, 3, 4, and 5 photon absorption at energies where the total ionization probability is near a maximum. For circular polarization the total and differential probabilities are consistently smaller compared to linear polarization as the number of photons absorbed is increased while keeping the radiation field intensity constant. For linear polarization, the total and differential probabilities vary substantially as a function of photons absorbed due to the presence of more absorption pathways.