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Development of apparatus for x-ray absorption spectroscopy of free clusters.

开发自由团簇的 X 射线吸收光谱仪。

基本信息

批准号：
12554013
负责人：
YAO Makoto
金额：
$ 8.83万
依托单位：
Kyoto University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2001
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-12554013/
关键词：
cluster X-ray absorption spectroscopy de-excitation process size selective

项目摘要

We have developed a new apparatus for X-ray absorption spectroscopy of free clusters and a new method for size selective EXAFS measurement of free clusters.The new apparatus mainly consists of two vacuum chambers, vacuum pumping system and cluster source. Each vacuum chamber is independently evacuated by turbo molecular pump to achieve enough pumping speed required for producing large clusters. In addition, we have developed a new cluster source which produces a cluster beam by an adiabatic expansion of gas or gas mixture into a vacuum chamber. The sample gas is ejected from the interchangeable nozzle which is mounted on top of a continuous flow cryostat. The nozzle temperature can be adjusted to values between 77 to 300 K and kept constant with an accuracy of ±1K when the cryostat is operated with liquid nitrogen. The performance of the apparatus have been evaluated by producing large argon clusters (up to Ar_<20> clusters are detected under typical condition).We have suggested a new … More method for size selective EXAFS measurement of free clusters by using the information of de-excitation process of clusters subsequent to the x-ray absorption. In order to examine our suggestion, we have developed a new data acquisition system for EXAFS-PEPICO synchronous measurement and carried out EXAFS-PEPICO synchronous measurements for Se cluster beam at the X-ray undulator beamline BL10XU in SPring-8. Although the number density of Se atoms in the cluster beam is smaller than that of bulk Se samples by more than ten orders of magnitude, the X- ray absorption spectrum which has been taken by total ion yield (TIY) mode indicates clear EXAFS oscillation. The partial ion yield (PIY) spectra which are obtained by integrating the peaks of the PEPICO spectra also show clear EXAFS oscillation. We have deduced EXAFS spectra of Se_2 and "Se_5" clusters according to the size selective EXAFS method. The EXAFS oscillation of "Se_5" differs from that of Se_2 in characteristic manner and the spacing of the EXAFS oscillation clearly demonstrates that the bond length of "Se_5" is longer than that of Se_2. More precisely, the former proves to be 2.35A and the latter 2.16A, which is fully consistent with a pile of EXAFS data for various forms of Se. Therefore, we may conclude that the proposed size-selective XAFS is a reliable and realistic method. Less

我们研制了一种新的自由团簇X射线吸收光谱装置和一种新的自由团簇尺寸选择EXAFS测量方法，该装置主要由两个真空室、抽真空系统和团簇源组成。每个真空室独立地由涡轮分子泵抽真空，以达到产生大团簇所需的足够抽速。此外，我们还研制了一种新的团簇源，它通过气体或气体混合物在真空室中的绝热膨胀产生团簇束。样品气体从安装在连续流低温恒温器顶部的可互换喷嘴喷出。当低温恒温器使用液氮运行时，喷嘴温度可调节至77至300 K之间的值，并保持恒定，精度为± 1 K。通过产生大的氩团簇（在典型条件下可探测到~ Ar_2团簇），对装置的性能进行了评价<20> ...更多信息利用原子团簇在X射线吸收后的退激发过程信息，对自由原子团簇进行尺寸选择性EXAFS测量。为了验证我们的建议，我们已经开发了一个新的数据采集系统的EXAFS-PEPICO同步测量，并进行了EXAFS-PEPICO同步测量硒团簇束在X射线波荡器束线BL 10 XU在SPring-8。虽然团簇束中Se原子的数密度比体Se样品的数密度小十个数量级以上，但用总离子产额（TIY）模式拍摄的X射线吸收谱显示出明显的EXAFS振荡。通过对PEPICO谱峰积分得到的部分离子产额（PIY）谱也显示出明显的EXAFS振荡。我们根据尺寸选择EXAFS方法推导了Se_2和“Se_5”团簇的EXAFS谱。“Se_5”的EXAFS振荡与Se_2的EXAFS振荡有特征性的不同，EXAFS振荡的间距清楚地表明“Se_5”的键长大于Se_2的键长。更准确地说，前者被证明是2.35A，后者是2.16A，这与一堆EXAFS数据的各种形式的硒完全一致。因此，我们可以得出结论，建议的尺寸选择性XAFS是一个可靠的和现实的方法。少