Slowdown and compression of a strong X-ray free-electron pulse propagating through the Mg vaporsYu-Ping Sun1, 2, Ji-Cai Liu1, 2 and Faris Gel'mukhanov1
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
received 15 July 2009; accepted in final form 9 September 2009; published September 2009
published online 2 October 2009
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 2p3/2-4s resonance (54.8 eV). The extensive ringing tail produced during propagation widens the power spectrum. This seed field triggers the Stokes channel 3s-2p3/2 (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.
42.65.Re - Ultrafast processes; optical pulse generation and pulse compression.
32.80.Aa - Inner-shell excitation and ionization.
41.60.Cr - Free-electron lasers.
© EPLA 2009