Saturable absorption of free-electron laser radiation by graphite near the carbon K-edge

Hoffmann, Lars; Jamnuch, Sasawat; Schwartz, Craig P.; Helk, T.; Raj, Sumana L.; Mizuno, H.; Mincigrucci, Riccardo; Foglia, Laura; Principi, Emiliano; Saykally, R. J.; Drisdell, Walter S.; Fatehi, Shervin; Pascal, Tod A.; Zuerch, Michael

doi:10.48550/arxiv.2112.12585

Cited by 1 publication

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“…Observations and theoretical calculations both suggest that the depletion of the core by an intense FEL pulse drives the SA effect, depending on the rate of the Auger decay, which is ~7 fs in graphite. At higher intensities TPA dominates at both photon energies with a different onset [30]. These results are useful to better understand soft X-ray absorption and scattering data at high intensities.…”

Section: -2-3 Saturable Absorption By Graphitementioning

confidence: 79%

“…Schematic view of the dominant processes of (c) second harmonic generation (SHG) and (d) two-photon absorption. I(ω) and I'(ω) represent the intensity of the incoming and transmitted beams, respectively [28][29][30].…”

Section: -2 Intense Fel Induced Nonlinear Effectsmentioning

confidence: 99%

“…The observation of nonlinear effects in graphite at the C K-edge was achieved at the EIS-TIMEX end station at the FERMI FEL-2 facility in different experiments [28][29][30]. Graphite samples 100-700 nm thick were exposed to a tunable soft X-ray seeded FEL pulse 25 fs (FWHM) long and with a spot size of 350 μm 2 at different photon energies: 260.5 eV (non-resonant), 284.18 eV or 285.7 eV (on-resonance), and 307 eV and 309.2 eV (above resonance).…”

Section: -2 Intense Fel Induced Nonlinear Effectsmentioning

confidence: 99%

“…The results showed that TPA is a bulk probe, possible in centrosymmetric systems, at soft X-ray energies, is element selective and similarly to SHG, is significantly enhanced for energies of the incident photon near the absorption edge of an atom of the material. It is also worth mentioning that the interpretation of TPA's strength can be hampered by FEL's energy fluctuations [28,30].…”

Section: -2-2 Two-photon Absorption By Graphitementioning

confidence: 99%

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Progress and Perspectives of Spectroscopic Studies at Carbon K-edge Using Novel Soft X-ray Pulsed Sources

Ebrahimpour¹,

Coreno²,

Giannessi³

et al. 2022

Preprint

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The development of novel coherent and brilliant sources, such as soft X-ray Free Electron Laser (FEL) and High Harmonic Generation (HHG) enables new ultrafast analysis of the electronic and structural dynamics of a wide variety of materials. Soft X-ray FEL delivers high brilliance beams with short pulse duration, high spatial coherence and photon energy tunability. In com-parison with FELs, HHG X-ray sources are characterized by a wide spectral bandwidth and few to sub-femtosecond pulses. The approach will lead to time-resolved reconstruction of molecular dynamics, shedding light on different photochemical pathways. The high peak brilliance of soft X-ray FELs facilitates investigations in nonlinear regime, while the broader spectral bandwidth of the HHG sources may provide the simultaneous probing of multiple components. Significant technical breakthroughs in these novel sources are under way to improve brilliance, pulse dura-tion, and to control spectral bandwidth, spot size, and energy resolution. Therefore, in the next few years, the new generation of soft X-ray sources combined with novel experimental tech-niques, new detectors, and computing capabilities will allow the study of several extremely-fast dynamics, such as vibronic dynamics. In the present review, we shortly discuss recent devel-opments in experiments, performed with soft X-ray FELs and HHG sources, operating near car-bon K-absorption edge, being a key atomic component in biosystems and soft materials. Differ-ent spectroscopy methods such as time-resolved pump-probe techniques, nonlinear spectrosco-pies and photoelectron spectroscopy studies have been addressed in an attempt of a better un-derstanding of fundamental physico-chemical processes

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Section: -2-3 Saturable Absorption By Graphitementioning

confidence: 79%

Section: -2 Intense Fel Induced Nonlinear Effectsmentioning

confidence: 99%