(a), (c) The dotted curves show two of the profiles fs(t) used in our simulations
Figure 1. (a), (c) The dotted curves show two of the profiles fs(t) used in our simulations. (b), (d) A sample of two random spiky pulses, typically produced in a single realization of the algorithm discussed in section 2, by superimposing Gaussian correlated noise (σω = 0.14 rad fs−1) with the deterministic profiles of (a) and (c). The solid curves in (a) and (c) show the average intensity \langle I_s(t)\rangle /I_s^{(0)} on a sample of 1000 random spiky pulses.
Abstract
Motivated by recent experiments pertaining to the interaction of weak SASE-free-electron-laser (FEL) pulses with atoms and molecules, we investigate the conditions under which such interactions can be described in the framework of a simple phase-diffusion model with decorrelated atom–field dynamics. The nature of the fluctuations that are inevitably present in SASE-FEL pulses is shown to play a pivotal role in the success of the decorrelation. Our analysis is performed in connection with specific recent experimental results from FLASH in the soft x-ray regime.