Numerical simulation of time delays in light-induced ionization

摘要

We apply a fundamental definition of time delay, as the difference between the time a particle spends withinna finite region of a potential and the time a free particle spends in the same region, to determine results fornphotoionization of an electron by an extreme ultraviolet laser field using numerical simulations on a grid. Ournnumerical results are in good agreement with those of theWigner-Smith time delay, obtained as the derivative ofnthe phase shift of the scattering wave packet with respect to its energy, for the short-range Yukawa potential. Innthe case of the Coulomb potential we obtain time delays for any finite region, while—as expected—the results donnot converge as the size of the region increases towards infinity. The impact of an ultrashort near-infrared probenpulse on the time delay introduced here is analyzed for both the Yukawa and the Coulomb potential and is foundnto be small for intensities below 1013 W/cm2.