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ヘリウムイオンの FEL 励起に伴う超蛍光、ヨーク超蛍光、自由誘 導減衰、四光波混合

ハリーズ ジェームズ, James Harries

Published Mar 17, 2019• 0 citations
OpenAlex

Abstract

We report the observation of superfluorescence at wavelengths of 469 nm, 164 nm and 30.4 nm from helium ions created and excited using pulses from the EUV free-electron laser at SACLA BL1. Experimental observations of intense, highly-directional emission (all 3 wavelengths) and a 1/(density) pulse delay dependence (469 nm emission), along with a detailed numerical simulation support our interpretations.

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Detailed study of superfluorescence at a wavelength of 469 nm from helium ionised and excited using free-electron laser pulses

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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.

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Superfluorescence, Free-Induction Decay, and Four-Wave Mixing: Propagation of Free-Electron Laser Pulses through a Dense Sample of Helium Ions

James Robert Harries, Hiroshi Iwayama, Susumu Kuma +9 more

We report an experimental and numerical study of the propagation of free-electron laser pulses (wavelength 24.3 nm) through helium gas. Ionization and excitation populates the He^{+} 4p state. Strong, directional emission was observed at wavelengths of 469, 164, 30.4, and 25.6 nm. We interpret the emissions at 469 and 164 nm as 4p-3s-2p cascade superfluorescence, that at 30.4 nm as yoked superfluorescence on the 2p-1s transition, and that at 25.6 nm as free-induction decay of the 3p state.

arXiv:1809.06503•Physical Review Letters•Dec 28, 2018•32 citations
We report the observation of superfluorescence at wavelengths of 469 nm, 164 nm and 30.4 nm from helium ions created and excited using pulses from the EUV free-electron laser at SACLA BL1. Experimental observations of intense, highly-directional emission (all 3 wavelengths) and a 1/(density) pulse delay dependence (469 nm emission), along with a detailed numerical simulation support our interpretations.
We report the probable observation of superfluorescence at a wavelength of 164 nm from helium ions created and excited using pulses from the EUV free-electron laser at SACLA BL1. The emission is the second step of a superfluorescence cascade from excited 4p states. To our knowledge this is the shortest wavelength at which superfluoresence has ever been demonstrated. The high intensity of the emission and the narrow angular divergence strongly support the interpretation as superfluorescence, and numerical simulations will also be presented which support this.
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.