Multiphoton ionization and multiphoton resonances in the tunneling regime

Journal Article · Sat May 15 00:00:00 EDT 2010 · Physical Review. A

DOI:https://doi.org/10.1103/PHYSREVA.81.053402· OSTI ID:21408839

Potvliege, R M; Mese, E; Vucic, Svetlana ^[1]

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1. Department of Physics, Durham University, South Road, Durham DH1 3LE (United Kingdom)

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}{sub 0} states akin to the Kramers-Henneberger states of the high-frequency Floquet theory. Within the single-active-electron approximation, these large-{alpha}{sub 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}{sup 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.

• OSTI ID: 21408839
• Journal Information: Physical Review. A, Vol. 81, Issue 5; Other Information: DOI: 10.1103/PhysRevA.81.053402; (c) 2010 The American Physical Society; ISSN 1050-2947
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
APPROXIMATIONS
ARGON
ATOMS
COUPLING
ELECTRONS
EXCITED STATES
GROUND STATES
HELIUM
HYDROGEN
LASER RADIATION
LENGTH
MONOCHROMATIC RADIATION
MULTI-PHOTON PROCESSES
PHOTOIONIZATION
RESONANCE
TUNNEL EFFECT
TUNNELING
WAVELENGTHS
CALCULATION METHODS
DIMENSIONS
ELECTROMAGNETIC RADIATION
ELEMENTARY PARTICLES
ELEMENTS
ENERGY LEVELS
FERMIONS
FLUIDS
GASES
IONIZATION
LEPTONS
NONMETALS
RADIATIONS
RARE GASES