Lorenz U, Kabachnik N M, Weckert E, Vartanyants I A
Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, D-22607 Hamburg, Germany.
Phys Rev E Stat Nonlin Soft Matter Phys. 2012 Nov;86(5 Pt 1):051911. doi: 10.1103/PhysRevE.86.051911. Epub 2012 Nov 21.
In single-particle coherent x-ray diffraction imaging experiments, performed at x-ray free-electron lasers (XFELs), samples are exposed to intense x-ray pulses to obtain single-shot diffraction patterns. The high intensity induces electronic dynamics on the femtosecond time scale in the system, which can reduce the contrast of the obtained diffraction patterns and adds an isotropic background. We quantify the degradation of the diffraction pattern from ultrafast electronic damage by performing simulations on a biological sample exposed to x-ray pulses with different parameters. We find that the contrast is substantially reduced and the background is considerably strong only if almost all electrons are removed from their parent atoms. This happens at fluences of at least one order of magnitude larger than provided at currently available XFEL sources.
在利用X射线自由电子激光（XFEL）进行的单粒子相干X射线衍射成像实验中，样品会受到高强度X射线脉冲照射以获取单次衍射图样。高强度会在系统中引发飞秒时间尺度上的电子动力学过程，这会降低所获衍射图样的对比度，并增加各向同性背景。我们通过对暴露于不同参数X射线脉冲下的生物样品进行模拟，来量化超快电子损伤导致的衍射图样退化情况。我们发现，只有当几乎所有电子都从其母原子中脱离时，对比度才会大幅降低且背景会变得相当强。这种情况发生时的注量比当前可用的XFEL源所提供的注量至少大一个数量级。
