We have examined the transmission of soft X-ray pulses from the FERMI free electron laser through carbon films of varying thickness, quantifying nonlinear effects of pulses above and below the carbon K-edge. At typical of soft X-ray free electron laser intensities, pulses exhibit linear absorption at photon energies above and below the K-edge, ∼308 and ∼260 eV, respectively; whereas two-photon absorption becomes significant slightly below the K-edge, ∼284.2 eV. The measured two-photon absorption cross section at 284.18 eV (∼6 × 10−48 cm4 s) is 7 orders of magnitude above what is expected from a simple theory based on hydrogen-like atoms – a result of resonance effects. © 2018
Titolo: | Two-photon absorption of soft X-ray free electron laser radiation by graphite near the carbon K-absorption edge |
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Data di pubblicazione: | 2018 |
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Handle: | http://hdl.handle.net/20.500.12079/4635 |
Appare nelle tipologie: | 1.1 Articolo in rivista |