Applications and Limits of Time-to-Energy Mapping of Protein Crystal Diffraction Using Energy-Chirped Polychromatic XFEL Pulses
Applications and Limits of Time-to-Energy Mapping of Protein Crystal Diffraction Using Energy-Chirped Polychromatic XFEL Pulses
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DOI：
10.3390/app10072599
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发表时间：
2020-04
期刊：
影响因子：
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通讯作者：
A. Fadini;S. Reiche;K. Nass;J. V. van Thor
中科院分区：
文献类型：
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作者：
A. Fadini;S. Reiche;K. Nass;J. V. van Thor
在瑞士自由电子激光器（FEL）上实现了宽带能量啁啾硬X射线脉冲，其带宽高达4%。我们考虑的特征参数的分析与能量啁啾脉冲的蛋白质衍射的时间依赖性。根据晶体镶嵌展度、会聚度和可记录分辨率的不同，在反射条件下，单个反射预计花费至少1.50阿秒和高达1.88飞秒。使用参数啁啾XFEL脉冲从4%的带宽条件下的模拟获得的，光线跟踪模拟已进行了演示跨个人的反射和分辨率范围的蛋白质晶体衍射的时间条纹。在较高的啁啾（10%）进行的模拟强调啁啾幅度的重要性，这将允许增加观测统计的时间分离的合并和结构确定的各个反射。最后，我们考虑使用啁啾脉冲衍射获得时间相关的观测的基本限制。我们认为，从啁啾SASE脉冲的瞬时带宽，可实现的最大理论时间分辨率为50-200的量级。然后，我们评估的能力，传播超快的光脉冲的泵浦-探测交叉相关的材料色散的特征条件下，在这方面，时间分辨率尺度与晶体厚度的限制因素。对于亚飞秒时间分辨率来说，尺寸小于几微米的晶体是必要的。
A broadband energy-chirped hard X-ray pulse has been demonstrated at the SwissFEL (free electron laser) with up to 4% bandwidth. We consider the characteristic parameters for analyzing the time dependence of stationary protein diffraction with energy-chirped pulses. Depending on crystal mosaic spread, convergence, and recordable resolution, individual reflections are expected to spend at least ≈ 50 attoseconds and up to ≈ 8 femtoseconds in reflecting condition. Using parameters for a chirped XFEL pulse obtained from simulations of 4% bandwidth conditions, ray-tracing simulations have been carried out to demonstrate the temporal streaking across individual reflections and resolution ranges for protein crystal diffraction. Simulations performed at a higher chirp (10%) emphasize the importance of chirp magnitude that would allow increased observation statistics for the temporal separation of individual reflections for merging and structure determination. Finally, we consider the fundamental limitation for obtaining time-dependent observations using chirped pulse diffraction. We consider the maximum theoretical time resolution achievable to be on the order of 50–200 as from the instantaneous bandwidth of the chirped SASE pulse. We then assess the ability to propagate ultrafast optical pulses for pump-probe cross-correlation under characteristic conditions of material dispersion; in this regard, the limiting factors for time resolution scale with crystal thickness. Crystals that are below a few microns in size will be necessary for subfemtosecond time resolution.