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A detailed investigation of single-photon laser enabled Auger decay in neon
Primož Rebernik Ribič, Giovanni De Ninno, 2019, original scientific article

Abstract: Single-photon laser enabled Auger decay (spLEAD) is an electronic de-excitation process which was recently predicted and observed in Ne. We have investigated it using bichromatic phase-locked free electron laser radiation and extensive angle-resolved photoelectron measurements, supported by a detailed theoretical model. We first used separately the fundamental wavelength resonant with the Ne+ 2s–2p transition, 46.17 nm, and its second harmonic, 23.08 nm, then their phase-locked bichromatic combination. In the latter case the phase difference between the two wavelengths was scanned, and interference effects were observed, confirming that the spLEAD process was occurring. The detailed theoretical model we developed qualitatively predicts all observations: branching ratios between the final Auger states, their amplitudes of oscillation as a function of phase, the phase lag between the oscillations of different final states, and partial cancellation of the oscillations under certain conditions.
Keywords: laser enabled Auger decay, free-electron lasers, neon
Published in RUNG: 12.01.2020; Views: 2716; Downloads: 0
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14.
Coherent soft X-ray pulses from an echo-enabled harmonic generation free-electron laser
Primož Rebernik Ribič, Giovanni De Ninno, 2019, original scientific article

Abstract: X-ray free-electron lasers (FELs), which amplify light emitted by a relativistic electron beam, are extending nonlinear optical techniques to shorter wavelengths, adding element specificity by exciting and probing electronic transitions from core levels. These techniques would benefit tremendously from having a stable FEL source, generating spectrally pure and wavelength-tunable pulses. We show that such requirements can be met by operating the FEL in the so-called echo-enabled harmonic generation (EEHG) configuration. Here, two external conventional lasers are used to precisely tailor the longitudinal phase space of the electron beam before emission of X-rays. We demonstrate high-gain EEHG lasing producing stable, intense, nearly fully coherent pulses at wavelengths as short as 5.9 nm (~211 eV) at the FERMI FEL user facility. Low sensitivity to electron-beam imperfections and observation of stable, narrow-band, coherent emission down to 2.6 nm (~474 eV) make the technique a prime candidate for generating laser-like pulses in the X-ray spectral region, opening the door to multidimensional coherent spectroscopies at short wavelengths.
Keywords: free electron laser, coherence, x-rays
Published in RUNG: 07.05.2019; Views: 3330; Downloads: 0
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15.
Laser heater commissioning at an externally seeded free-electron laser
Simone Spampinati, Giovanni De Ninno, 2014, original scientific article

Keywords: free electron laser, relativistic electrons, electron heating
Published in RUNG: 01.03.2016; Views: 4387; Downloads: 191
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