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

本项目的目的是试制一种适用于低频区的高灵敏度分子束傅里叶变换微波光谱仪。这一区域的光谱适用于包括两个或三个苯环的较大分子的高分辨光谱(作为许多生物分子的一部分)。首先，我们对我们的光谱仪进行了改进，将分子束的方向改为平行于微波传播。这一改进是由格拉博(德国基尔大学)和洛瓦斯(美国NIST)提出的，我们对以前的水平有了更高的敏感性。第二步，我们构造了一个带有两个凹面镜的法布里-珀罗腔。一个反射镜固定在圆柱体上，圆柱体通过真空箱的法兰孔来回运动，用于调谐频率。它很容易加热像生物分子一样的固体样品。经过几次试验，我们遇到了一些关于镜面布置和调谐的严重问题。现在，我们正在尝试设计和制造一种新的型号：(1)在真空箱的外侧设置两条精密导轨，并以直角的方式连接到两个法兰上。(2)两个大镜子(直径：550 mm)分别固定在法兰上。(3)利用专用工具，以较低的成本制作了大型反射镜。购买了频率自动扫频机构的电子元件，并搭建了电路。这个项目的最终目的是确定生物分子和水之间的络合物的分子结构，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光谱仪测量了这些配合物的光谱，但无法获得谱线。应该开发用于固体样品的新技术，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.