Ion/molecule reactions in the orifice-skimmer region of an atmospheric pressure Penning ionization mass spectrometer

摘要: Atmospheric pressure Penning ionization mass spectra of methanol were measured as functions Ar or He gas in the first vacuum chamber, position skimmer, and voltage applied between orifice skimmer. When skimmer coaxial with a distance 4 mm, distribution CH3OH2+(CH3OH)n clusters was only weakly dependent on both (in range 19-220 Pa) orifice-skimmer 1-45 V). The ion/molecule reaction CH3OH2+ + CH3OH --> CH3+(CH3OH) H2O observed free jet expansion, especially at high values. off-centered them increased to 18 formation large clusters, well their dissociation, seen. endothermic proton transfer reaction, CH3OCH3, occurred voltage. collision-induced dissociation cluster ions by chamber much more efficient than Ar. These results demonstrated that are highly spectrometry do not necessarily reflect abundance produced atmospheric ion source.