Resonance-enhanced three-photon single ionization of Ne by ultrashort extreme-ultraviolet pulses

繁政 英治*; 永園 充*; 岩山 洋士*; Harries, J.; 石川 理沙*

Journal of Physics B; Atomic, Molecular and Optical Physics, 46(16), p.164020_1 - 164020_5, 2013/08

https://doi.org/10.1088/0953-4075/46/16/164020

Time-resolved extreme-ultraviolet (EUV) fluorescence spectroscopy has been applied to study the multi-photon, single ionization of Ne irradiated by intense EUV-free-electron laser (FEL) pulses at a wavelength of 51 nm. A broad, intense peak at a wavelength of around 46 nm is observed, which is shorter than the incident FEL wavelength. The time-dependence of the fluorescence reveals that the peak has two un-resolved components, which we attribute to the decay of the excited ion states Ne2s(S) and 2p(P)3s(P) at 46.0 nm and 44.6 nm. From the observed intensity ratios and fluorescence lifetimes we conclude that the Ne 2p (P)3s(P) state is populated by two-photon resonance-enhancement, via a 2p3p doubly-excited state of Ne.