We present a theoretical study of temporal, spectral, and spatial reshaping of intense, ultrafast x-ray pulses propagating through a resonant medium. Our calculations are based on the solution of a three-dimensional time-dependent Schrödinger-Maxwell equation, with the incident x-ray photon energy on resonance with the core-level $1s\text{−}3p$ transition in neon. We study the evolution of the combined incident and medium-generated field, including the effects of stimulated emission, absorption, ionization, and Auger decay, as a function of the input pulse energy and duration. We find that stimulated Raman scattering between core-excited states $1s^{-1}3p$ and $2p^{-1}3p$ occurs at high x-ray intensity, and that the emission around this frequency is strongly enhanced when also including the similar $1s^{-1}\text{−}2p^{-1}$ response of the ion. We also explore the dependence of x-ray self-induced transparency (SIT) and self-focusing on the pulse intensity and duration, and we find that the stimulated Raman scattering plays an important role in both effects. Finally, we discuss how these nonlinear effects may potentially be exploited as control parameters for pulse properties of x-ray free-electron laser sources.

中文翻译：

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X射线从线性状态到非线性状态的共振传播

我们目前对通过共振介质传播的强烈，超快X射线脉冲的时间，光谱和空间整形进行理论研究。我们的计算基于与时间有关的三维三维Schrödinger-Maxwell方程的解，其中入射x射线光子能量在与核能级共振时发生$\mathrm{1个}s\text{-}3p$霓虹灯过渡。我们研究了入射场和中场相结合场的演化，包括受激发射，吸收，电离和俄歇衰减的影响，它是输入脉冲能量和持续时间的函数。我们发现核心激发态之间的受激拉曼散射$\mathrm{1个}{s}^{-\mathrm{1个}}3p$ 和 $2p^{-\mathrm{1个}}3p$ 发生在高X射线强度下，并且当包含类似的 $\mathrm{1个}{s}^{-\mathrm{1个}}\text{-}2p^{-\mathrm{1个}}$离子的响应。我们还探索了X射线自感应透明度（SIT）和自聚焦对脉冲强度和持续时间的依赖性，我们发现受激拉曼散射在这两种效应中都起着重要作用。最后，我们讨论了如何将这些非线性效应潜在地用作X射线自由电子激光源脉冲特性的控制参数。