Recoil-Ion Momentum Distributions for Two-Photon Double Ionization of He and Ne by 44 eV Free-Electron Laser Radiation

• DOI: 10.1103/physrevlett.101.073003
• Publication Date: 2008-08-15T19:36:55Z
• Authors: A. Rudenko; L. Foucar; M. Kurka; Th. Ergler; K. U. Kühnel; Y. H. Jiang; A. Voitkiv; B. Najjari; A. Kheifets; S. Lüdemann; T. Havermeier; M. Smolarski; S. Schössler; K. Cole; M. Schöffler; R. Dörner; S. Düsterer; W. Li; B. Keitel; R. Treusch; M. Gensch; C. D. Schröter; R. Moshammer; J. Ullrich
• Keywords: Ions; Two photons; Image segmentation; Ionization; Photons; info:eu-repo/classification/ddc/550; Keywords: Absorption; Lasers; T; Two-electron reactions; Electrons; Neon; Nonsequential; Helium; 7. Clean energy; 01 natural sciences; Ion momentum; Dynamics; Reaction microscopes; Multiphoton processes; Free-electron lasers; 0103 physical sciences; Emission dynamics

Recoil-ion momentum distributions for two-photon double ionization of He and Ne (variant Planck's over omega=44 eV) have been recorded with a reaction microscope at FLASH (the free-electron laser at Hamburg) at an intensity of approximately 1 x 10(14) W/cm2 exploring the dynamics of the two fundamental two-photon-two-electron reaction pathways, namely, sequential and direct (or nonsequential) absorption of the photons. We find strong differences in the recoil-ion momentum patterns for the two mechanisms pointing to the significantly different two-electron emission dynamics and thus provide serious constraints for theoretical models.