TY - JOUR
T1 - Single-atom response of helium atoms to pulses from an EUV free-electron laser
T2 - Implications for the subsequent development of superfluorescence
AU - Harries, James R.
AU - Ohae, Chiaki
AU - Kuma, Susumu
AU - Nakajima, Kyo
AU - Togashi, Tadashi
AU - Miyamoto, Yuki
AU - Sasao, Noboru
AU - Iwayama, Hiroshi
AU - Nagasono, Mitsuru
AU - Yabashi, Makina
AU - Shigemasa, Eiji
N1 - Funding Information:
This work was supported in part by the Research Foundation for Opto-Science and Technology and a JSPS KAKENHI grant (Grant No. 15K04707). We are grateful for access to JAEA computing facilities.
PY - 2016/12/22
Y1 - 2016/12/22
N2 - 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.
AB - 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.
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U2 - 10.1103/PhysRevA.94.063416
DO - 10.1103/PhysRevA.94.063416
M3 - Article
AN - SCOPUS:85007108777
VL - 94
JO - Physical Review A - Atomic, Molecular, and Optical Physics
JF - Physical Review A - Atomic, Molecular, and Optical Physics
SN - 1050-2947
IS - 6
M1 - 063416
ER -