Ionization of a multilevel atom by ultrashort laser pulses |
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Authors: | A V Andreev S Yu Stremoukhov and O A Shutova |
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Institution: | 1.Physics Department,Moscow State University,Moscow,Russia;2.International Education and Research Center,Moscow State University,Moscow,Russia |
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Abstract: | Specific features of ionization of single atoms by laser fields of a near-atomic strength are investigated. Calculations are
performed for silver atoms interacting with femtosecond laser pulses with wavelengths λ = 800 nm (Ti:Sapphire) and λ = 1.064
μm (Nd:YAG). The dependences of the probability of ionization and of the form of the photoelectron energy spectra on the field
of laser pulses for various values of their duration are considered. It is shown that the behavior of the probability of ionization
in the range of subatomic laser pulse fields is in good agreement with the Keldysh formula. However, when the field strength
attains values close to the atomic field strength, the discrepancies in these dependences manifested in a decrease in the
ionization rate (ionization stabilization effect) or in its increase (accelerated ionization) are observed. These discrepancies
are associated with the dependence of the population dynamics of excited discrete energy levels of the atom on the laser pulse
field amplitude. |
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