[1] R. B. Vrijen, L. D. Noordam. Rydberg X-ray laser based on inner-electron optical-field ionization. J. Opt. Sec. Am. (B), 1996, 13(1): 189~196
[2] D. Cubaynes, S. Diehl, L. Journel et al.. First photoexcitation measurements and R-matrix calculations of even-parity hollow states in laser-excited lithium atoms. Phys. Rev. Lett., 1996, 77(11): 2194~2197