Ionização induzida por impacto de elétrons e fragmentação iônica de álcoois primários metanol e etanol

Abstract

The ionization and ion fragmentation of methanol and ethanol induced by electron impact were investigated in this work, using a HIDEN quadrupole mass spectrometer. Once, it is the first time that this spectrometer was used in the Atomic and Molecular Spectroscopy Laboratory (LEAM) at UFJF, the work began with the characterization of the apparatus, for subsequent application on the required studies. In studies of alcohols were obtained mass spectra and relative abundances of the cations generated by electron with energy impact of 70eV, where it was recorded that CH2O+H was the most abundant cation for methanol and for ethanol. The Total Ionization Cross Section (TICS) to methanol and the partial ionization cross sections (PICS) for the cations CH3O+H, CH3+, CH2+, CH2O+H, CO+H CH2O+, CO+, C+, CH+ were generated for electron impact energies of 10-100 eV. Our results are in good agreement with the theoretical and experimental values reported in literature, for most of the formed cations. It was also reported PICS values for ions groups for comparison with measurement of Rejoub et al., who reported data with lower resolution than was recorded in this work. For ethanol, was obtained TICS and also, PICS for the cations CH3CH2O+H, CH3CHO+H, CH3CHO+, C2H3O+, C2H2O+, C2HO+, CH3O+H, CH2O+H, CH2O+, C2H5+, CO+ or C2H4+, C2H3+, C2H2+, C2H+, C2+, O2+ or CH4+, CH3+, CH2+, CH+ and C+. To our knowledge, these are the first PICS measurement reported in the literature for each individual cation. The only possible comparison was with ion groups, reported by Rejoub et al. Finally, the ionization thresholds for methanol and ethanol for the formed cations were generated in this work.