Single-atom response of helium atoms to pulses from an EUV free-electron laser: Implications for the subsequent development of superfluorescence

James R. Harries, Chiaki Ohae, Susumu Kuma, Kyo Nakajima, Tadashi Togashi, Yuki Miyamoto, Noboru Sasao, Hiroshi Iwayama, Mitsuru Nagasono, Makina Yabashi, Eiji Shigemasa

    Research output: Contribution to journalArticlepeer-review

    3 Citations (Scopus)

    Abstract

    Using multilevel (161-level) numerical simulations beyond the rotating-wave approximation, we investigate the single-atom response of helium to intense pulses of radiation with properties characteristic of a self-amplified spontaneous emission (SASE) free-electron laser (FEL) source, and central wavelengths resonant with 1snp excitation (n=3,4). The results show a complete breakdown of the two-level approximation and suggest that, under typical experimental conditions, levels other than the resonant level are significantly populated. We discuss the implications for the subsequent development of superfluorescence (a collective effect) from the excited atomic medium and compare the results to recent experiments.

    Original languageEnglish
    Article number063416
    JournalPhysical Review A
    Volume94
    Issue number6
    DOIs
    Publication statusPublished - Dec 22 2016

    ASJC Scopus subject areas

    • Atomic and Molecular Physics, and Optics

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