Two-photon absorption of soft X-ray free electron laser radiation by graphite near the carbon K-absorption edge

Lam, Royce K.; Raj, Sumana L.; Pascal, Tod A.; Pemmaraju, C. D.; Foglia, Laura; Simoncig, Alberto; Fabris, Nicola; Miotti, Paolo; Hull, C.J.; Rizzuto, Anthony M.; Smith, Jacob W.; Mincigrucci, Riccardo; Masciovecchio, C.; Gessini, Alessandro; Ninno, G. De; Diviacco, B.; Roussel, Eléonore; Spampinati, S.; Penco, G.; Mitri, S. Di; Trovò, M.; Danailov, M. B.; Christensen, Steven T.; Sokaras, Dimosthenis; Weng, Tsu‐Chien; Coreno, Marcello; Poletto, Luca; Drisdell, Walter S.; Giannessi, L.; Principi, Emiliano; Nordlund, Dennis; Saykally, Richard J.; Schwartz, Craig P.

doi:10.1016/j.cplett.2018.05.021

Cited by 11 publications

(23 citation statements)

References 30 publications

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“…More recent experiments do report a total ionization cross section which is extracted from measurements of ion or fluorescence yields, however, more often than not, the corresponding uncertainty cannot be estimated. While some of these experimental cross sections seem to be in agreement with theory [3][4][5][6] within an order of magnitude [7,8], other [9,10] report values of even two or three orders of magnitude larger than theoretically calculated predictions. There are few measurements which were reported with the experimental uncertainties [11][12][13], however, since second-order processes depend quadratically on the incoming beam intensity, the uncertainties in measured cross sections are strongly affected by beam parameters which determine the absolute intensity.…”

supporting

confidence: 65%

Fluorescence polarization as a precise tool for understanding nonsequential many-photon ionization

2019

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Nonsequential two-photon ionization of inner-shell np subshell of neutral atoms by circularly polarized light is investigated. Detection of subsequent fluorescence as a signature of the process is proposed and the dependence of fluorescence degree of polarization on incident photon beam energy is studied. It is generally expected that the degree of polarization remains approximately constant, except when the beam energy is tuned to an intermediate n ′ s resonance. However, strong unexpected change in the polarization degree is discovered for nonsequential two-photon ionization at specific incident beam energy due to a zero contribution of the otherwise dominant ionization channel. Polarization degree of the fluorescence depends less on the beam parameters and its measurements at this specific beam energy, whose position is very sensitive to the details of the employed theory, are highly desirable for evaluation of theoretical calculations of nonlinear ionization at hitherto unreachable accuracy.

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supporting

confidence: 65%

Fluorescence polarization as a precise tool for understanding nonsequential many-photon ionization

2019

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“…This is significant, as very few experiments have been able to directly measure the properties of the ablation plume on ultrafast timescales. In future work, we hope to study the scattering over broader angle and time ranges, effecting the direct study of both the growth and structural composition of the nanomaterials in the ablation plumes; this will facilitate a deeper understanding of the factors controlling the properties and morphology of nanomaterials produced by laser ablation, and will provide a valuable complement to the femtosecond second harmonic generation 35 and two-photon absorption 36 experiments that we recently demonstrated with free electron laser sources in the soft X-ray region. The sample is mounted on a diffractometer and aligned at grazing incidence relative to the X-ray pulse.…”

Section: Discussionmentioning

confidence: 99%

Early time dynamics of laser-ablated silicon using ultrafast grazing incidence X-ray scattering

Hull

Raj

Lam

et al. 2019

Chemical Physics Letters

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Controlling the morphology of laser-derived nanomaterials is dependent on developing a better understanding of the particle nucleation dynamics in the ablation plume. Here, we utilize the femtosecond-length pulses from an x-ray free electron laser to perform time-resolved grazing incidence x-ray scattering measurements on a laser-produced silicon plasma plume. At 20 ps we observe a dramatic increase in the scattering amplitude at small scattering vectors, which we attribute to incipient formation of liquid silicon droplets. These results demonstrate the utility of XFELs as a tool for characterizing the formation dynamics of nanomaterials in laser-produced plasma plumes on ultrafast timescales.

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“…Nowadays, it is also possible to probe these systems in nonlinear regime with free-electron lasers 3,4 . That is why, in the last decade, much of experimental efforts [5][6][7][8][9][10][11][12][13][14][15] have been paid to studying the fundamental properties of nonlinear light-matter interaction, and finding use in applied fields such as nonlinear spectroscopy. The theoretical developments were in many respects following the experimental trail.…”

Section: Introductionmentioning

confidence: 99%

Breakdown of the electric dipole approximation at Cooper minima in direct two-photon ionisation

Hofbrucker¹,

Volotka²,

Fritzsche³

2020

Sci Rep

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We predict breakdown of the electric dipole approximation at nonlinear Cooper minimum in direct two-photon K−shell atomic ionisation by circularly polarised light. According to predictions based on the electric dipole approximation, we expect that tuning the incident photon energy to the Cooper minimum in two-photon ionisation results in pure depletion of one spin projection of the initially bound 1s electrons, and hence, leaves the ionised atom in a fully oriented state. We show that by inclusion of electric quadrupole interaction, dramatic drop of orientation purity is obtained. The low degree of the remaining ion orientation provides a direct access to contributions of the electron-photon interaction beyond the electric dipole approximation in the two-photon ionisation of atoms and molecules. The orientation of the photoions can be experimentally detected either directly by a Stern-Gerlach analyzer, or by means of subsequent Kα fluorescence emission, which has the information about the ion orientation imprinted in the polarisation of the emitted photons. 2/113/11

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Two-photon absorption of soft X-ray free electron laser radiation by graphite near the carbon K-absorption edge

Cited by 11 publications

References 30 publications

Fluorescence polarization as a precise tool for understanding nonsequential many-photon ionization

Fluorescence polarization as a precise tool for understanding nonsequential many-photon ionization

Early time dynamics of laser-ablated silicon using ultrafast grazing incidence X-ray scattering

Breakdown of the electric dipole approximation at Cooper minima in direct two-photon ionisation

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