Yazar "Potvliege, R. M." seçeneğine göre listele

Listeleniyor 1 - 2 / 2
  • [ X ]
    Öğe
    Multiphoton ionization and multiphoton resonances in the tunneling regime
    (Amer Physical Soc, 2010) Potvliege, R. M.; Mese, E.; Vucic, Svetlana
    The rate of ionization of an atom of helium, argon, or hydrogen exposed to an intense monochromatic laser field and the quasienergy spectrum of their dressed states are studied for values of the Keldysh parameter between 1 and 0.6 and wavelengths between 390 and 1300 nm. The calculations are carried out within the non-Hermitian Floquet theory. Resonances with intermediate excited states significantly affect ionization from the dressed ground state at all the intensities and all the wavelengths considered. The dressed excited states responsible for these structures are large-alpha(0) states akin to the Kramers-Henneberger states of the high-frequency Floquet theory. Within the single-active-electron approximation, these large-alpha(0) states become species independent at sufficiently high intensity or sufficiently long wavelength. Apart for the resonance structures arising from multiphoton coupling with excited states, the ab initio Floquet ionization rate is in excellent agreement with the predictions of two different calculations in the strong field approximation, one based on a length-gauge formulation of this approximation and one based on a velocity-gauge formulation. The calculations also confirm the validity of the omega(2) expansion as an alternative to the strong field approximation for taking into account the nonadiabaticity of the ionization process in intense low-frequency laser fields.
  • [ X ]
    Öğe
    The quasienergy spectrum of argon from 400 to 800 nm
    (Iop Publishing Ltd, 2007) Meşe, Emine; Potvliege, R. M.; 0009-0001-0120-4721
    The Floquet quasienergy spectrum of argon atoms exposed to a strong laser field is presented for incident wavelengths of 400, 600, and 800 nm and electron excursion amplitudes up to 30 a.u. The calculation is performed by diagonalizing the Floquet Hamiltonian on a discrete basis of Sturmian functions, the atom being described by a one-electron model potential. How the quasienergies of the dressed bound states change as functions of both the wavelength and the intensity of the incident field is studied. The spectrum of the dressed excited states varies slowly with these two parameters, apart for a number of changes between direct and avoided crossings and for less frequent, more profound reorganizations. The spectrum converges at high intensity towards that predicted by the high-frequency Floquet theory.