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51.
Polycapillary‐optics‐based micro‐XANES and micro‐EXAFS at a third‐generation bending‐magnet beamline
Geert Silversmit Bart Vekemans Sergey Nikitenko Wim Bras Viktoria Czhech Gyula Zaray Imre Szaloki Laszlo Vincze 《Journal of synchrotron radiation》2009,16(2):237-246
A focusing system based on a polycapillary half‐lens optic has been successfully tested for transmission and fluorescence µ‐X‐ray absorption spectroscopy at a third‐generation bending‐magnet beamline equipped with a non‐fixed‐exit Si(111) monochromator. The vertical positional variations of the X‐ray beam owing to the use of a non‐fixed‐exit monochromator were shown to pose only a limited problem by using the polycapillary optic. The expected height variation for an EXAFS scan around the Fe K‐edge is approximately 200 µm on the lens input side and this was reduced to ~1 µm for the focused beam. Beam sizes (FWHM) of 12–16 µm, transmission efficiencies of 25–45% and intensity gain factors, compared with the non‐focused beam, of about 2000 were obtained in the 7–14 keV energy range for an incoming beam of 0.5 × 2 mm (vertical × horizontal). As a practical application, an As K‐edge µ‐XANES study of cucumber root and hypocotyl was performed to determine the As oxidation state in the different plant parts and to identify a possible metabolic conversion by the plant. 相似文献
52.
Ye Tao Yan Huang Zhenghua Gao Hao Zhuang Aiyu Zhou Yinglei Tan Daowu Li Shuaishuai Sun 《Journal of synchrotron radiation》2009,16(6):857-863
The new 4B8 beamline provides UV–VUV light in the wavelength range from 360 to 120 nm. It uniquely enables two kinds of spectroscopy measurements: synchrotron radiation circular dichroism spectroscopy and VUV excited fluorescence spectroscopy. The former is mainly used in protein secondary structure studies, and the latter in VUV excited luminescent materials research. Remote access to fluorescence measurement has been realised and users can collect data online. Besides steady‐state measurements, fluorescence lifetime measurements have been established using the time domain method, while a laser‐induced temperature jump is under development for protein folding dynamics using circular dichroism as a probe. 相似文献
53.
Zhenyu Tian 《Proceedings of the Combustion Institute》2009,32(1):311-318
A premixed nitromethane/oxygen/argon flame at low pressure (4.67 kPa) has been investigated using tunable vacuum ultraviolet (VUV) photoionization and molecular-beam mass spectrometry. About 30 flame species including hydrocarbons, oxygenated and nitrogenous intermediates have been identified by measurements of photoionization efficiency spectra. Mole fraction profiles of the flame species have been determined by scanning burner position at some selected photon energies. The results indicate that N2 and NO are the major nitrogenous products in the nitromethane flame. Compared with previous studies on nitromethane combustion, a number of unreported intermediates, including C3H4, C4H6, C4H8, C2H2O, C2H4O, CH3CN, H2CNHO, C3H3N and C3H7N, are observed in this work. Based on our experimental results and previous modeling studies, a detailed oxidation mechanism including 69 species and 314 reactions has been developed to simulate the flame structure. Despite some small discrepancies, the predictions by the modeling study are in reasonable agreement with the experimental results. 相似文献
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极紫外、软X-射线变线距平面光栅单色仪的研究 总被引:3,自引:2,他引:1
高性能极紫外、软X射线单色仪的研制对高亮度同步辐射光源的应用具有十分重要的意义。对Itou的变线距平面光栅单色仪作了详细的分析研究,发现它的光栅工作曲线几乎与单色仪的入、出射臂长度等参量无关,仅取决于单色仪设计的边界条件。其曲线方程和SX-700单色仪的完全类似。该单色仪不仅具有很好的光栅效率和高级次谐波抑制性能,而且有利于几条光束线共享一个电子储存环窗口的光路优化设计。 相似文献
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Vacuum ultraviolet photoabsorption spectra of CH3I 6s and 6s′ Rydberg states doped into supercritical argon, krypton, and xenon perturbers were measured from low density to the density of the triple point liquid at noncritical temperatures and on an isotherm near the perturber critical temperature. A full line shape analysis of these spectra was performed using a single set of intermolecular potential parameters for each dopant/perturber system. The resulting perturber induced shift of the simulated adiabatic transition of the 6s and 6s′ Rydberg states is presented as a function of perturber number density, and this shift illustrates a perturber critical point effect on the excitation energies of the molecular low-n Rydberg states. 相似文献
59.
Photon-induced dissociation pathways of thymine are investigated with vacuum ultraviolet photoionization mass spectrometry and theoretical calculations. The photoionization mass spectra of thymine at different photon energy are measured and presented. By selecting suitable photon energy, exclusively molecular ion m/z=126 is obtained. At photon energy of 12.0 eV, the major ionic fragments at m/z=98, 97, 84, 83, 70, and 55 are obtained, which are assigned to C4H6N24O+、C4H5N2O+、C3H4N2O+(or C4H6NO+)、C4H5NO+、C2NO2+ and C3H5N+, respectively. With help of theoretical calculations, the detailed dissociation pathways of thymine at low energy are well established. 相似文献
60.
单色仪在实际光谱测量前需要进行波长校准。文中分析了波长驱动原理,并推导了Czerny-Turner双光栅单色仪出射波长与步进电机脉冲数的关系式。在此基础上进行了波长校准实验。使用低压汞灯作为校准光源,在紫外波段和可见波段蓝端,扫描多条低压汞灯特征谱线,得到单色仪的指示波长与信号强度的关系数据。计算出单色仪出射这些谱线时使用的波长修正量。最后使用曲线拟合方法得到250 nm~450 nm光谱范围内单色仪出射任意波长时对应修正量的计算式。波长校准保证了单色仪的波长准确性。 相似文献