Anomalous nonlinear X-ray Compton scattering

Authors

Matthias Fuchs, University of Nebraska-LincolnFollow
Mariano Trigo, SLAC National Accelerator LaboratoryFollow
Jian Chen, SLAC National Accelerator LaboratoryFollow
Shambhu Ghimire, SLAC National Accelerator LaboratoryFollow
Sharon Shwartz, Bar Ilan UniversityFollow
Michael Kozina, SLAC National Accelerator LaboratoryFollow
Mason Jiang, SLAC National Accelerator Laboratory
Thomas Henighan, SLAC National Accelerator LaboratoryFollow
Crystal Bray, SLAC National Accelerator LaboratoryFollow
Georges Ndabashimiye, SLAC National Accelerator Laboratory
Philip H. Bucksbaum, SLAC National Accelerator LaboratoryFollow
Yiping Feng, SLAC National Accelerator LaboratoryFollow
Sven Herrmann, SLAC National Accelerator LaboratoryFollow
Gabriella A. Carini, SLAC National Accelerator LaboratoryFollow
Jack Pines, SLAC National Accelerator Laboratory
Philip Hart, SLAC National Accelerator Laboratory
Christopher Kenney, SLAC National Accelerator LaboratoryFollow
Serge Guillet, SLAC National Accelerator LaboratoryFollow
Sébastien Boutet, SLAC National Accelerator LaboratoryFollow
Garth J. Williams, SLAC National Accelerator Laboratory
Marc Messerschmidt, SLAC National Accelerator LaboratoryFollow
M. Marvin Seibert, SLAC National Accelerator Laboratory
Stefan Moeller, SLAC National Accelerator LaboratoryFollow
Jerome B. Hastings, SLAC National Accelerator LaboratoryFollow
David A. Reis, SLAC National Accelerator LaboratoryFollow

Date of this Version

2015

Document Type

Article

Citation

Published in Nature Physics 11 (2015), pp 964–970. doi 10.1038/nphys3452

Comments

© 2015 Macmillan Publishers Limited. Used by permission.

Abstract

X-ray scattering is typically used as a weak linear atomic-scale probe of matter. At high intensities, such as produced at free-electron lasers, nonlinearities can become important, and the probe may no longer be considered weak. Here we report the observation of one of the most fundamental nonlinear X-ray–matter interactions: the concerted nonlinear Compton scattering of two identical hard X-ray photons producing a single higher-energy photon. The X-ray intensity reached 4 × 10²⁰ W cm⁻², corresponding to an electric field well above the atomic unit of strength and within almost four orders of magnitude of the quantum-electrodynamic critical field. We measure a signal from solid beryllium that scales quadratically in intensity, consistent with simultaneous non-resonant two-photon scattering from nearly-free electrons. The high-energy photons show an anomalously large redshift that is incompatible with a free-electron approximation for the ground-state electron distribution, suggesting an enhanced nonlinearity for scattering at large momentum transfer.