Novel laboratory spectrometer for pump-probe NEXAFS spectrometry of bio-molecules in solution

提出的NEXAFS（近边缘x射线吸收精细结构）光谱仪旨在促进溶液中生物分子的时间分辨分析。在叶绿素铜（CuChl）模型系统的帮助下，探讨光合色素-蛋白质复合物的结构-功能关系。此外，将展示在大型设施上独立进行泵浦探针实验的可能性。该概念是基于由申请人开发的用于软x射线区域的激光产生等离子体（LPP）源，具有高能量分辨率的高效反射带板，大型CCD相机和用于溶液的传输液体电池。反射带板的设计以及液体电池的开发是拟议项目的一部分。该光谱仪将针对CuChl组分（C、O、N的K吸收边和Cu的LIII边）进行优化，在LPP源的几个单脉冲中提供高光谱分辨率（E/DE~1000）、高信噪比（SNR~100）的NEXAFS光谱。因此，整个装置将使在实验室中对溶液中的生物样品进行调查成为可能，到目前为止，这种调查必须在同步辐射设施中进行。NEXAFS光谱仪将在传输模式下工作，因此有助于在测量过程中在线监测降解过程。此外，为了获得光禁跃迁的信息，将利用光泵和软x射线脉冲探测x射线光双共振（XODR）的变化。为此目的，将在设置中实现一个泵通道。新型光谱仪使时间分辨测量，作为光学元件，如果适合于fs光谱。为了实现fs时间尺度，光谱仪可以与其他源一起使用，例如与max - born研究所合作的HHG源。

The proposed development of a NEXAFS (Near edge x-ray absorption fine structure) spectrometer aims to facilitate time-resolved analysis of bio-molecules in solution. The structure-function relationship of photosynthetic pigment-protein complexes will be explored with the help of the model system copper chlorophyllin (CuChl). Additionally the possibility of pump-probe experiments independent on large scale facilities will be shown.The concept is based on a laser-produced plasma (LPP) source for the soft x-ray region which was developed by the applicant, highly efficient reflections zone plates with high energetic resolution, a large scale CCD camera and a transmission liquid cell for solutions. The design of the reflection zone plates as well as the development of the liquid cell is part of the proposed project.The spectrometer will be optimized for the components of CuChl (K absorption edges of C, O, N, and LIII edge of Cu), delivering NEXAFS spectra with high spectral resolution (E/DE~1000), high signal-to-noise ratio (SNR~100) in a few single pulses of the LPP source.The whole setup will thus enable the investigations of biological samples in solution in the laboratory, which up until now had to be performed at synchrotron radiation facilities. The NEXAFS spectrometer will operate in transmission mode, thus, facilitating on-line monitoring of degradation processes during measurements.In addition, to gain information about optically forbidden transitions X-ray optical double resonance (XODR) investigations will be performed by using an optical pump and probing the changes with the soft X-ray pulse. For this purpose a pump channel will be implemented in the setup.The novel spectrometer enables time-resolved measurements, as the optical element if suited for fs-spectroscopy. For the realization of fs-time scales the spectrometer can be used with other sources, for example HHG sources in cooperation with the Max-Born-Institute.