Measuring energy-dependent photoelectron escape in microcrystals.
Measuring energy-dependent photoelectron escape in microcrystals.
复制标题
测量微晶体中能量相关的光电子逃逸。
DOI：
10.1107/s2052252519016178
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发表时间：
2020
期刊：
影响因子：
3.9
通讯作者：
Storm SLS
中科院分区：
文献类型：
--
作者：
Storm SLS
随着在同步辐射X射线光束线上使用微晶体和强流微束的趋势越来越大，辐射损伤问题变得更加紧迫。理论计算表明，主要造成破坏的光电子可以逃逸微晶体。这种效应会随着晶体尺寸的减小以及能量的增加而变得更加明显。为了证明这一效应，用Pilatus CdTe 2M探测器收集了尺寸为5×3×3和20×8×8 µm的低温冷却溶菌酶晶体在13.5keV和20.1keV下的数据，这两种探测器在两个能量下具有相似的量子效率。在实验和X射线微束表征后，通过扫描电子显微镜直接测量单个晶体的尺寸，计算出准确的吸收剂量。然后基于d1/2度量对晶体寿命进行了量化。在这项首次系统研究中，观察到较小晶体的晶体寿命更长，并且在较高的X射线能量下晶体寿命增加，支持了光电子逃逸的理论预测。使用专门为20 keV以上能量的数据收集而优化的探测器技术，使理论上预测的光电子逃逸得以量化和利用，指导未来的光束线设计选择。
With the increasing trend of using microcrystals and intense microbeams at synchrotron X-ray beamlines, radiation damage becomes a more pressing problem. Theoretical calculations show that the photoelectrons that primarily cause damage can escape microcrystals. This effect would become more pronounced with decreasing crystal size as well as at higher energies. To prove this effect, data from cryocooled lysozyme crystals of dimensions 5 × 3 × 3 and 20 × 8 × 8 µm mounted on cryo-transmission electron microscopy (cryo-TEM) grids were collected at 13.5 and 20.1 keV using a PILATUS CdTe 2M detector, which has a similar quantum efficiency at both energies. Accurate absorbed doses were calculated through the direct measurement of individual crystal sizes using scanning electron microscopy after the experiment and characterization of the X-ray microbeam. The crystal lifetime was then quantified based on the D1/2 metric. In this first systematic study, a longer crystal lifetime for smaller crystals was observed and crystal lifetime increased at higher X-ray energies, supporting the theoretical predictions of photoelectron escape. The use of detector technologies specifically optimized for data collection at energies above 20 keV allows the theoretically predicted photoelectron escape to be quantified and exploited, guiding future beamline-design choices.