Development of pulsed molecular beam EI-TOFMS and its application to intracluster ion-molecule reaction

Abstract

Part A. Electron-Impact Ionization Time-of-Flight Mass Spectrometer A versatile electron-impact time-of-flight mass spectrometer (EI-TOFMS) in a pulsed molecular beam has been constructed. The instrument contains a fast rise time, square pulse generator, biased at high voltage, which simplifies the implementation of EI-TOFMS. Power field effect transistors are used as the active switching element, which afford compact size and simplified circuit construction. The effect of the shape of the repelling pulse on the flight time and space focusing condition is estimated by numerical calculation. Preliminary test results are provided for pulsed molecular beams of ammonia and hydrogen iodide. Part B. Electron-Impact Ionization Mass Spectroscopic Studies of Acetylene and Mixed Acetylene-Ammonia Clusters as a Structure Probe Ion-molecule reactions of acetylene and mixed acetylene-ammonia cluster ions are studied using an electron impact time-of-flight mass spectrometer. The mass spectroscopic evidence for the enhanced structural stabilities of [$C_6H_4ㆍ(NH_3)_m^{+}$] (m=0-8) ions is also found along with the detection of mixed cluster $[(C_2H_2)ㆍ(NH_3)_m]^{+}$ ions, which gives insight into the feasible structure of solvated ions. This is rationalized on the basis of the structural stability for acetylene clusters and the dissoceation dynamics of the complex ion under the presence of solvent molecules. Part C. Influence of Ammonia Solvation on the Structural Stability of Ethylene Cluster Ions. The stable structures of pure ethylene and mixed ethylene-ammonia cluster ions are studied using an electron impact ionization time-off-light mass spectrometer. Investigations on the relative cluster ion distributions of $(C_2H_4)n(NH_3)_m^{+}$ under various experimental conditions suggest that $(C_2H_4)_2(NH_3)_3^{+}$ and $(C_2H_4)_3(NH_3)_2^{+}$ ions have the enhanced structural stabilities, which give insight into the feasible structure of solvated ions. For the stable con...