[1] Li X F, L′Huillier A, Ferray M et al.. Multiple-harmonic generation in rare gases at high laser intensity. Phys. Rev. (A), 1989, 39(11):5751~5761
[2] Lompre L A, L′Huillier A, Ferray M et al.. High-order harmonic generation in xenon: Intensity and propagation effects. J. Opt. Soc. Am. (B), 1990, 7(5):754~761
[5] Krause J, Schafer K J,Kulander K C. High-order harmonic generation from atoms and ions in the high intensity regime. Phys. Rev. Lett., 1992, 68(24):3535~3538
[6] Chang Zenghu, Rundquist A, Wang Haiwen et al.. Generation of coherent soft X rays at 2.7 nm using high harmonics. Phys. Rev. Lett., 1997, 79(16):2967~2970
[9] Ammosov M V, Delone N B, Krainov V P. Tunnel ionization of complex atoms and of atomic ions in an alternating electromagnetic field. Sov. Phys. JETP, 1986, 64(6):1191~1194