@misc{oai:repo.qst.go.jp:00074814,
 author = {ハリーズ, ジェームズ and Harries, James},
 month = {Oct},
 note = {We have studied in detail the emission of superfluorescence at a wavelength of 469 nm (4p→3s) from helium ions created and excited using free-electron laser pulses from SACLA’s BL1. In earlier work we observed superfluorescence at visible wavelengths in neutral helium [1-5]. To observe superfluorescence from helium ions we used a wavelength of 24.3 nm, resonant with the He + 1s→4p
transition and sufficiently short to ionise neutral helium atoms. The density of excited He + ions created by this sequential 2-photon absorption was sufficient to allow for the development of superfluoresence., 原子衝突学会第43回年会},
 title = {Detailed study of superfluorescence at a wavelength of 469 nm from helium ionised and excited using free-electron laser pulses},
 year = {2018}
}