Trial production of automatic sweep Fourier transform microwave spectrometer designed for 1GHz region

本项目的目的是试制一台适用于低频区的高灵敏度分子束傅里叶转移微波谱仪。这一波段的光谱适合于对含有两个或三个苯环的大分子（许多生物分子的一部分）进行高分辨光谱分析。Grabow（基尔大学，德国）和Lovas（NIST，美国）的方法，得到了更高的灵敏度。一个反射镜固定在圆柱体上，圆柱体通过真空罐的法兰孔来回移动，用于调谐频率。对生物分子这样的固体样品进行加热是很容易的。经过几次试验，我们遇到了一些严重的镜面排列和调整问题，现在我们正在尝试设计和制作一个新的模型：（1）在真空罐的外侧设置两个精密的轨道，并以直角连接到两个法兰上。(2)两个大镜子（直径：550 mm）分别固定在法兰上。(3)用专用的工具可以制作出大尺寸的反射镜，成本低。2购买了频率自动扫描机构的电子元器件，并进行了电路的搭建。本项目的最终目的是确定生物分子与水的复合物的分子结构，具体的例子是苯甲酸和水，以及邻苯二酚和水。我们已经尝试用旧的FTMW光谱仪测量这些配合物的光谱，但不能获得光谱线。应开发新的固体样品技术，包括激光烧蚀。

The purpose of this project is a trial production of a sensitive molecular beam Fourier transfer microwave spectrometer designed for low frequency region. Spectrum in this region is suitable for high resolution spectroscopy of rather large molecule including two or three benzene rings( as a part of many biomolecules).At first, we improved our spectrometer to be change the direction of molecular beam to be parallel that of microwave propagation. This improvement was advised by Grabow (Kiel Uni., Germany) and Lovas (NIST, USA) and we got more sensitivity to previous level.Second step we constructed a Fabry-Perot cavity with two concave mirrors. One mirror fixed to cylinder which moved for and back through a flange hole of vacuum tank for tuning the frequency. It was easy to heat a solid sample like biomolecule. After several trials, we met some serious problems about mirror arrangement and tuning.Now we are trying to design and make a new model ; (1) two precise rails are set up out side of the vacuum tank and attached to both flanges on right angle. (2) two large mirrors (diameter : 550mm) fixed to Flange respectively. (3) we can make a large mirror by special tool on low expense.The electronic parts for frequency auto sweep mechanism were purchased and set up the circuit. A control program was obtained from NIST group and transferred to our system.Our final purpose of this project is to determine a molecular structure of the complex between biomolecule and water for concrete examples are benzoic acid and water, and catechol and water. We have already tried to measure spectrum of these complexes using old FTMW spectrometer, however could not obtain the spectral lines. New technique for a solid sample should be developed, including laser ablation.