• Direct two-photon double ionization of H2 

      Simonsen, A. S.; Sørngård, Stian Astad; Nepstad, Raymond; Førre, Morten (Peer reviewed; Journal article, 2012-06-05)
      We have studied the process of direct (nonsequential) two-photon double ionization of molecular hydrogen (H2). Solving the time-dependent Schr¨odinger equation by an ab initio method, total (generalized) and singledifferential ...
    • Femtosecond-pulse-train ionization of Rydberg wave packets 

      Simonsen, Sigrid Ina; Sørngård, Stian Astad; Førre, Morten; Hansen, Jan Petter (Peer reviewed; Journal article, 2012-10-09)
      We calculate, based on first-order perturbation theory, the total and differential ionization probabilities from a dynamic periodic Rydberg wave packet of a given n-shell exposed to a train of femtosecond laser pulses. The ...
    • High-order harmonic generation from graphene: Strong attosecond pulses with arbitrary polarization 

      Sørngård, Stian Astad; Simonsen, Sigrid Ina; Hansen, Jan Petter (Peer reviewed; Journal article, 2013-05-03)
      We explore high-order harmonic generation (HHG) from a graphene sheet exposed to intense femtosecond laser pulses based on the Lewenstein model. It is demonstrated that the HHG cutoff frequency increases with graphene size ...
    • The ionization dynamics of atoms and molecules exposed to short pulses 

      Sørngård, Stian Astad (Doctoral thesis; Peer reviewed, 2013-08-29)
      The electrons ejected in an ionization event initiated by an incident laser pulse carry detailed information about the structure and the correlation intrinsic to atoms and molecules. This information is essential for our ...
    • Multiphoton ionization and stabilization of helium in superintense xuv fields 

      Sørngård, Stian Astad; Askeland, Sigurd; Nepstad, Raymond; Førre, Morten (Peer reviewed; Journal article, 2011)
      Multiphoton ionization of helium is investigated in the superintense field regime, with particular emphasis on the role of the electron-electron interaction in the ionization and stabilization dynamics. To accomplish this, ...
    • Stabilization of circular Rydberg atoms by circularly polarized infrared laser fields 

      Askeland, Sigurd; Sørngård, Stian Astad; Pilskog, Ingjald; Nepstad, Raymond; Førre, Morten (Peer reviewed; Journal article, 2011-09-29)
      The ionization dynamics of circular Rydberg states in strong circularly polarized infrared (800 nm) laser fields is studied by means of numerical simulations with the time-dependent Schr¨odinger equation. We find that at ...