Interest in atomic scale structures of individual specimens has invigorated developments of high-resolution probes, which include single-particle imaging using x-ray free-electron lasers (XFELs). The demonstrated spatial resolution, however, remains at tens of nanometers with difficulty in collecting diffraction signals at high frequency distinguished from noises. As such, various resolution-enhancement methods have been introduced, but few experimental verifications are available. Here, by carrying out XFEL single-pulse diffraction experiments, we explicitly unveil the dependence of SNRs on incident x-ray flux, data averaging, or multiparticle interference. We further propose a data-accumulation method of resolution-shell averaging as a robust scheme to improve the SNR. This study establishes a roadmap with which high-resolution XFEL single-pulse experiments can be contrived.

中文翻译：

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飞秒X射线激光对单个样品的结构研究：增强信噪比的途径

对单个标本的原子尺度结构的兴趣促进了高分辨率探针的发展，其中包括使用X射线自由电子激光（XFEL）的单粒子成像。然而，已证明的空间分辨率仍保持在几十纳米，难以收集不同于噪声的高频衍射信号。这样，已经引入了各种分辨率增强方法，但是很少有实验验证可用。在这里，通过执行XFEL单脉冲衍射实验，我们明确揭示了SNR对入射X射线通量，数据平均或多粒子干扰的依赖性。我们进一步提出了一种分辨率-壳平均的数据累积方法，作为提高信噪比的可靠方案。