[1] [1] K. Burnett, V. C. Reed, P. L. Knight. Atoms in ultra-intense laser fields. J. Phys. B, 1993, 26: 561

[2] [2] L. R. Franco, A. Sanpera, M. L. Pons et al.. Photoionization of hydrogen atom: Three-dimensional results and pseuido-one-dimensional model. Phys. Rev., 1991, A44: 4652

[3] [3] V. C. Reed, K. Burnett. Ionization of atoms in intense laser pulses using the kramers-Henneberger transformation. Phys. Rev., 1990, A42: 3152

[4] [4] R. R. Freeman, P. H. Bucksbaum, Milchberg H. et al.. Above-threshold ionization with subpicosecond laser pulses. Phys. Rev. Lett., 1987, 59(10): 1092

[5] [5] S. Augst, D. D. Meyerhofer, D. Strickland et al.. Laser ionization of noble gases by coulomb barrier suppression. J. Opt. Soc. Am., 1991, B8: 858

[6] [6] K. J. Schafer, K. C. Kulander. Phase-dependent effect in multiphoton ionization induced by a laser field and its second harmonic. Phys. Rev., 1992, A45(11): 8026

[7] [7] P. M. Potvliege, P. H. G. Smith. Two-colour multiphoton ionization of hydrogen by an intense laser and one of its harmonics. J. Phys., 1992, B25: 2501

[8] [8] Suxing Hu, Zhizhan Xu. Energy enhancement of harmonic photons with a half-period-delayed pulse. Appl. Phys. Lett., 1997, 70(9), to be published