飛行時間形質量分析計におけるRPDイオン源の特性,およびトリオキシメチレンのイオン化電圧,出現電圧の測定

概要

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Characteristics of the RPD ionization source which is used to measure the ionization and the appearance potentials, have been studied using Time-of-Flight mass spectrometer. By selecting appropriate potentials of the electrodes of the RPD electron gun, monochromatic electron beam having about 0.1 eV energy spread, has been obtained with an efficiency of 23% of total electron current. It has been confirmed that this ionization source is useful to measure the appearance potential, by measuring the ionization efficiency curve of the Kr+ ion.The ionization efficiency curves of the parent and several main fragment ions produced from the trioxymethylene (Tox) by electron impact, have also been measured from a stand-point of radiation chemistry. The lst ionization potential of the parent ion (10.59±0.05 eV) coincides with the lst appearance pointial of the (M-1)+ ion. In the ionization efficiency curve of the parent ion, a hump, which is attributed to autoionization process, is found at 0.3 eV above the threshold of the lst ionization potential. In the ionization efficiency curve of the CH2OCH20H+ ion, the curve at the lst onset shows the shape of step function, that is considered to show the autoionization or ion-pair production process. Some pronounced bresks have also been observed in the ionization efficiency curves. The results have been discussed together with the information of metastable ion peakes observed by the conventonal mass spectrometer.