Negative-Ion Mass Spectrometry by Use of Collisional Ionization of High-Rydberg Atoms

本研究项目是利用高里德堡原子碰撞电离建立负离子质谱学。这种电离方法的基本原理是利用Rg^&lt；**&gt的最外层电子碰撞转移到靶分子上，其效率是电子碰撞电离效率的10^4倍。此外，由于电子的动能很小(10-20 meV)，与电子附着相关的过剩能量可以被最小化。随后的研究表明，这种电离方法适用于弱结合聚合物分子和具有正垂直电子键的分子的质量分析。H_2O、NH_3、CH_3CN、(CH_3)_2CO、SF_6、CO_2、N_2O等稀有气体团簇与电子碰撞产生的高里德堡氪原子的碰撞电离。由此产生的负离子的质谱学研究表明，碰撞电子转移为有效和温和地产生负团簇离子提供了一种独特的方法。一种配备高里德堡原子源的负离子质谱仪的研制根据第一节所述的电离方法制作的离子源安装在日本石油株式会社中央技术研究实验室的JEOL磁扇区型质谱仪上，对谷氨酸、戊二烯、苯并三唑等几个样品进行了检测，并获得了这些物种的母体负离子。

This research project was undertaken to establish a negative-ion mass spectrometry by use of collisional ionization of high-Rydberg agtoms. The basic principle of this ionization method is to use the outermost electron of Rg^<**> which is collisionally transferred to a target molecule with an efficiency 10^4 times as high as that for electron-impact ionization. In addition, the excess energy associated with the electron attachment can be minimized because of a small kinetic energy of the electron (10 - 20 meV). The following studies showed that this method of ionization is applicable as an ion source for the mass analysis of weakly-bound polymer molecules and molecular having postive vertical electron affinities.1. Studies on electron transfer from high-Rydberg rare gas atoms to van der Waals clustgersvan der Weals clusters of H_2O, NH_3, CH_3CN, (CH_3)_2CO, SF_6, CO_2, N_2O etc. wre ionized in collision with high -Ryodgerg Krypton atoms produced by electron impact. The mass spectroscopiec studies of negative ions thus produced revealed that the collisional electgron transfer provides a unique method for efficient and gentle production of negative cluster ions.2. Development of a negative-ion mass spectrometer equipped with a high-Ryodberg atom sourceAn ion source based on the ionization method mentioned in section 1 was made and mounted to a JEOL magnetic sector-type mass spectrometer of the central Technical Research Laboratory of NIPPON OIL Co., Ltd. Several samples, such as glutamic acid, perylene, benztriazole etc., wre examined and the parent negative ions of these species were obtained.