Establishing nonlinearity thresholds with ultraintense X-ray pulses

• DOI: 10.1038/srep33292
• Publication Date: 2016-09-13T11:22:34Z
• Authors: Jakub Szlachetko; Joanna Hoszowska; Jean-Claude Dousse; Maarten Nachtegaal; Wojciech Błachucki; Yves Kayser; Jacinto Sà; Marc Messerschmidt; Sebastien Boutet; Garth J. Williams; Christian David; Grigory Smolentsev; Jeroen A. van Bok...; Bruce D. Patterson; Thomas J. Penfold; Gregor Knopp; Marek Pajek; Rafael Abela; Christopher J. Milne
• Keywords: Photon energy; Free electron model

Abstract X-ray techniques have evolved over decades to become highly refined tools for a broad range of investigations. Importantly, these approaches rely on measurements that depend linearly the number incident photons. The advent free electron lasers (XFELs) is opening ability reach extremely high photon numbers within ultrashort pulse durations and leading paradigm shift in our explore nonlinear signals. However, enormous increase peak power double-edged sword with new exciting methods being developed but at same time well-established proving unreliable. Consequently, accurate knowledge about threshold signals essential. Herein we report an spectroscopic study reveals important details thresholds interactions. By varying both intensity energy, establish regimes which simplest process, two-photon absorption (TPA), can be observed. From extract probability this process as function energy confirm nature sub-femtosecond lifetime virtual intermediate electronic state.