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 journalArticle

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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