Abstract
The nonlinear absorption mechanisms of neon atoms to intense, femtosecond kilovolt x rays are investigated. The production of is observed at x-ray frequencies below the , absorption edge and demonstrates a clear quadratic dependence on fluence. Theoretical analysis shows that the production is a combination of the two-photon ionization of ground state and a high-order sequential process involving single-photon production and ionization of transient excited states on a time scale faster than the Auger decay. We find that the nonlinear direct two-photon ionization cross section is orders of magnitude higher than expected from previous calculations.
- Received 13 December 2010
DOI:https://doi.org/10.1103/PhysRevLett.106.083002
© 2011 American Physical Society
Synopsis
A double whammy of x rays
Published 4 March 2011
Scientists have for the first time observed two-photon absorption with x rays.
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