Nonlinear Atomic Response to Intense Ultrashort X Rays

作者：Doumy G^*; Roedig C; Son S K; Blaga C I; DiChiara A D; Santra R; Berrah N; Bostedt C; Bozek J D; Buck**aum P H; Cryan J P; Fang L; Ghimire S; Glownia J M; Hoener M; Kanter E P; Kraessig B; Kuebel M; Messerschmidt M; Paulus G G; Reis D A; Rohringer N; Young L; Agostini P; DiMauro L F

来源：Physical Review Letters, 2011, 106(8): 083002.

DOI：10.1103/PhysRevLett.106.083002

The nonlinear absorption mechanisms of neon atoms to intense, femtosecond kilovolt x rays are investigated. The production of Ne(9+) is observed at x-ray frequencies below the Ne(8+), 1s(2) absorption edge and demonstrates a clear quadratic dependence on fluence. Theoretical analysis shows that the production is a combination of the two-photon ionization of Ne(8+) ground state and a high-order sequential process involving single-photon production and ionization of transient excited states on a time scale faster than the Auger decay. We find that the nonlinear direct two-photon ionization cross section is orders of magnitude higher than expected from previous calculations.

• 出版日期2011-2-24