Abstract
We built a double-beam mass spectrometer whose ion source has a dual parallel electron beams which are only 5 mm apart and variable in their energy, 0∼150eV. This instrument is useful to detect not only ionic fragments but also neutral species and excited molecules(or atoms)produced by electron impact. This paper describes the highly excited Ar, whose threshold energy is about 15.6 eV. It was found that this excited Ar had long life-time more than 10-5 sec, getting through the repeller net and ionizing chamber as a neutral with its thermal energy and was ionized by the effect of ion accelerating field, namely field ionization. Theoretical consideration was also discussed.
