Slowdown and compression of a strong X-ray free-electron pulse propagating through the Mg vapors

¹  Theoretical Chemistry, Royal Institute of Technology - Roslagstullsbacken 15, S-106 91 Stockholm, Sweden, EU
²  College of Physics and Electronics, Shandong Normal University - 250014 Jinan, China

Corresponding author: jicai@theochem.kth.se

Received: 15 July 2009
Accepted: 9 September 2009

Abstract

Here we study the propagation of a strong X-ray free-electron pulse through the resonant medium of atomic Mg accompanied by the self-seeded stimulated resonant X-ray Raman scattering. The X-ray pulse is decelerated by two orders of magnitude because of nonlinear interaction and experiences a 6-fold compression. The simulations are based on a strict numerical solution of the coupled Bloch and Maxwell equations for a 50 fs pulse tuned in the - resonance (54.8 eV). The extensive ringing tail produced during propagation widens the power spectrum. This seed field triggers the Stokes channel - (49.4 eV) of stimulated resonant X-ray Raman scattering and the weaker Stokes and anti-Stokes fields caused by four-wave mixing. The beating between the Stokes and pump fields quenches the population inversion at longer propagation distances where lasing without inversion enhances the Stokes component.