CONCENTRATION ENRICHMENT IN THE ION-SOURCE OF A PULSED ELECTRON-BEAM HIGH-PRESSURE MASS-SPECTROMETER

Citation
Ds. Mcgrew et al., CONCENTRATION ENRICHMENT IN THE ION-SOURCE OF A PULSED ELECTRON-BEAM HIGH-PRESSURE MASS-SPECTROMETER, International journal of mass spectrometry and ion processes, 139, 1994, pp. 47-58
Citations number
12
Categorie Soggetti
Spectroscopy,"Physics, Atomic, Molecular & Chemical
ISSN journal
01681176
Volume
139
Year of publication
1994
Pages
47 - 58
Database
ISI
SICI code
0168-1176(1994)139:<47:CEITIO>2.0.ZU;2-C
Abstract
The magnitude of concentration enrichment of methyl iodide in methane, helium, and argon buffer gases within the ion source of a pulsed e-be am high pressure mass spectrometer (PHPMS) is characterized here by a theoretical model and by kinetic measurements of the gas phase ion/mol ecule reaction, F- + CH3I --> CH3F + I-, at 150-degrees-C. A relativel y simple PHPMS ion source is used in which the magnitude of enrichment is related only to the ventilation of individual molecules out of the ion source by passage through its ion exit and electron entrance slit s. It is shown that significant enrichment does occur under typical op erating conditions of this source and that the magnitude of enrichment is strongly dependent on the choice of ion source pressure. These obs ervations are explained in terms of the flow conditions thought to exi st in the ion source. Recommendations for improving the accuracy of fu ture kinetic and equilibrium measurements by the PHPMS are provided.