Infrared-laser-assisted photoionization of helium by coherent extreme ultraviolet light

We investigate the infrared (IR)-laser-assisted photoionization of He by a coherent extreme ultraviolet (euv) light solving the time-dependent Schroedinger equation. A combined field of the 13th and 15th harmonics created from the same IR laser source is used to ionize He atoms coherently. We show t...

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Bibliographic Details
Published in:Physical review. A, Atomic, molecular, and optical physics Atomic, molecular, and optical physics, 2010-04, Vol.81 (4), Article 043429
Main Authors: Tong, Xiao-Min, Toshima, Nobuyuki
Format: Article
Language:English
Subjects:
AMPLITUDES
ATOMIC AND MOLECULAR PHYSICS
CONTROL
DIFFERENTIAL EQUATIONS
ELECTROMAGNETIC RADIATION
ELEMENTS
EQUATIONS
EXTREME ULTRAVIOLET RADIATION
FLUIDS
GASES
HARMONICS
HELIUM
IONIZATION
LASERS
NONMETALS
OSCILLATIONS
PARTIAL DIFFERENTIAL EQUATIONS
PHOTOIONIZATION
PROBABILITY
PULSES
RADIATIONS
RARE GASES
SCHROEDINGER EQUATION
TIME DELAY
TIME DEPENDENCE
ULTRAVIOLET RADIATION
WAVE EQUATIONS
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Summary:We investigate the infrared (IR)-laser-assisted photoionization of He by a coherent extreme ultraviolet (euv) light solving the time-dependent Schroedinger equation. A combined field of the 13th and 15th harmonics created from the same IR laser source is used to ionize He atoms coherently. We show that the ionization probabilities oscillate as a function of the time delay between the IR and the euv pulses. On the other hand, the oscillation amplitude increases as the IR intensity increases, reaches a maximum when the IR intensity is around 6x10{sup 12} W/cm{sup 2}, and then decreases as the IR intensity increases further. Decomposing the ionization probabilities by the 13th and 15th harmonics, we illustrate that the oscillation amplitude is small for a lower IR laser intensity due to the fact that the transition strength by the 13th harmonic is much smaller than the one by the 15th harmonic. When the IR intensity increases further above 6x10{sup 12} W/cm{sup 2}, the transition strength by the 13th harmonic becomes larger than the one by the 15th harmonic and the oscillation amplitude is reduced again. By tuning the relative field strengths of the 13th and 15th harmonics or the IR intensity, we can control the oscillation amplitude.
ISSN:1050-2947
1094-1622
DOI:10.1103/PhysRevA.81.043429