A simple scheme is proposed and experimentally confirmed to generate X‐ray free‐electron lasers (XFELs) consisting of broadband and narrowband beams with a controllable intensity ratio and a large photon‐energy separation. This unique two‐color XFEL beam will open new opportunities for investigation of nonlinear interactions between intense X‐rays and matter.

中文翻译：

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宽带和窄带光束组成的双色X射线自由电子激光器

提出了一种简单的方案，并通过实验证实了该方案可以生成由宽带和窄带光束组成的X射线自由电子激光器（XFEL），它们的强度比可控且光子能量分离大。这种独特的双色XFEL光束将为研究强X射线与物质之间的非线性相互作用提供新的机会。