Addressing the ultrafast coherent evolution of electronic wave functions has long been a goal of nonlinear x-ray physics. A first step toward this goal is the investigation of stimulated x-ray Raman scattering (SXRS) using intense pulses from an x-ray free-electron laser. Earlier SXRS experiments relied on signal amplification during pulse propagation through dense resonant media. By contrast, our method reveals the fundamental process in which photons from the primary radiation source directly interact with a single atom. We introduce an experimental protocol in which scattered neutral atoms rather than scattered photons are detected. We present SXRS measurements at the neon K edge and a quantitative theoretical analysis. The method should become a powerful tool in the exploration of nonlinear x-ray physics.

解决电子波函数的超快速相干演变一直是非线性X射线物理学的目标。朝此目标迈出的第一步是研究使用来自X射线自由电子激光器的强脉冲进行的受激X射线拉曼散射（SXRS）。较早的SXRS实验依赖脉冲在通过密集谐振介质传播期间的信号放大。相比之下，我们的方法揭示了基本过程，其中来自主要辐射源的光子直接与单个原子相互作用。我们介绍了一种实验协议，其中检测到散射的中性原子而不是散射的光子。我们介绍了霓虹灯K边缘的SXRS测量和定量理论分析。该方法应成为探索非线性X射线物理学的有力工具。