Mass Spectrometric Study of Photoionization. II. Mass Spectra by the Use of Resonance Lines of Argon and Helium

Abstract

Abstract An emission line of He II was generated at 304 Å (40.80 eV) from a microwave plasma light source operated in the standing wave mode. On the other hand, the plasma without the standing wave mode emits only the resonance line of He I at 584 Å (21.21 eV). A resonance line of Ar I was emitted at 1048 Å (11.82 eV) by argon carrier gas flowing through a capillary tube. The mass spectra of propane, n-butane, propylene, benzene, and isoamyl acetate obtained by the use of the emission line of He II at 304 Å were not very different from those of the electron impact method at 50 eV. The positive-charge distribution on each atom of the ionized molecules is estimated from the total ion yield of the molecule. In the fragmentation processes of isoamyl acetate, the intensity of the fragment ion (CH3CO+) including carbonyl group rose rapidly with the increase in the photon energies obtained by the resonance lines of Ar I, He I, and He II. At these photon energies, the ratios of the fragment ion, CH3CO+ , to that of C5H10+ were 0.17, 0.43 and 2.0 respectively.