Atomic excitation during recollision-free ultrafast multi-electron tunnel ionization

Ian Williams, W.A. Bryan, J. McKenna, S.L. Stebbings, E.M.L. English, M. Suresh, J. Wood, Balasingam Srigengan, I.C.E. Turcu, J.M. Smith, E.J. Divall, C.J. Hooker, A.J. Langley, J.L. Collier, W.R. Newell

Research output: Contribution to journalArticlepeer-review

74 Citations (Scopus)


Modern intense ultrafast pulsed lasers generate an electric field of sufficient strength to permit tunnel ionization of the valence electrons in atoms(1). This process is usually treated as a rapid succession of isolated events, in which the states of the remaining electrons are neglected(2). Such electronic interactions are predicted to be weak, the exception being recollision excitation and ionization caused by linearly polarized radiation(3). In contrast, it has recently been suggested that intense field ionization may be accompanied by a two-stage 'shake-up' reaction(4). Here we report a unique combination of experimental techniques(5-8) that allows us to accurately measure the tunnel ionization probability for argon exposed to 50-fs laser pulses. Most significantly for the current study, this measurement is independent of the optical focal geometry(7,8), equivalent to a homogenous electric field. Furthermore, circularly polarized radiation negates recollision. The present measurements indicate that tunnel ionization results in simultaneous excitation of one or more remaining electrons through shake-up(9). From an atomic physics standpoint, it may be possible to induce ionization from specific states, and will influence the development of coherent attosecond extreme-ultraviolet-radiation sources(10). Such pulses have vital scientific and economic potential in areas such as high-resolution imaging of in vivo cells and nanoscale extreme-ultraviolet lithography.
Original languageEnglish
Pages (from-to)379-383
Number of pages5
JournalNature Physics
Issue number6
Publication statusPublished - May 2006

ASJC Scopus subject areas

  • General Physics and Astronomy


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