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25 September 1995 Photoionization and residual energy in ultrashort-pulse laser
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The above-threshold ionizations (ATI) in intense laser field are studied by the methods of S- matrix and classical dynamics, respectively. It is shown that from the viewpoint of gauge invariance, the Keldysh theory is more reliable than Reiss theory. Then, the Keldysh theory is developed further to satisfy the law of parity conservation and to give more reasonable results. The ionization rate predicted by classical dynamics is in agreement with tunneling theory as the field strength is near and above threshold field and approaches Keldysh's rate as the field strength is higher than threshold field. The space charge effect is analyzed using the technique of multiple-time-scale perturbation. It is found that the effect on residual energy is great as the half plasma period is larger than pulse length or the plasma density approaches critical density, however, it cannot reduce the ATI energy significantly over whole density range. Finally, it is pointed out that for a given pump laser there may be a density range available for optical field ionization (OFI) x-ray laser over which only the ATI heating plays a role.
© (1995) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Shigang Chen, Jie Liu, Dehai Bao, and Bryan Nie "Photoionization and residual energy in ultrashort-pulse laser", Proc. SPIE 2520, Soft X-Ray Lasers and Applications, (25 September 1995);

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