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## Interaction of Atomic Hydrogen with Pico- and Femtosecond Laser Pulsesby
Jonathan Parker
The interaction of hydrogen with femtosecond pulses is studied at field intensities as high as 2.2×10 A population-trapping effect is found numerically and modeled theoretically. Despite the high field intensities, population representing the excited electron is recaptured from the ionization continuum by bound states during the excitation. Population returns to the atom with just the right phase to strongly inhibit ionization. A theory is presented that models this effect for a variety of laser pulse shapes, with and without the rotating-wave approximation. The numerical integration reveals that a certain amount of above-threshold ionization (ATI) occurs. A theory similar to the Keldysh-type theories of ATI is developed. The theory differs from the Keldysh theories in that, like Schrodinger's equation, it is invariant under certain gauge transformations. The proposed theory gives far superior agreement with the numerical integration than Keldysh theory.
Classical ionization at 2.2×10
Web page maintained by Hideomi Nihira ( nihira@optics.rochester.edu ). Last modified 13 September 2006 |