Pulsed high pressure mass spectrometry with near-viscous flow ion sampling

• Published in: International journal of mass spectrometry and ion processes Vol. 154; no. 1; pp. 15 - 24
• Main Authors: Williamson, D.H., Knighton, W.B., Grimsrud, E.P.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 1996
• Subjects: High pressure ion source; Ion sampling; Ion/molecule reaction rate constants; Pulsed electron beam ion source; Viscous flow; Ion/molecule reaction rate constants; Ion sampling; High pressure ion source; Pulsed electron beam ion source; Viscous flow
• ISSN: 0168-1176; 1873-2801
• DOI: 10.1016/0168-1176(96)04372-8

Rate constants for the reaction, F − + CH 3I → CH 3F + I −, are determined at 150°C by pulsed electron beam high pressure mass spectrometry (PHPMS) under conditions where the ions within the source are sampled by near-viscous flow through ion-exit apertures of relatively large diameter. It is shown that the rate constants thereby determined are of high accuracy and are not subject to a common source of measurement error that is intrinsic to PHPMS measurements made under the molecular or near-molecular flow conditions that are generally used. The success of ion sampling by near-viscous flow demonstrated here also suggests that the PHPMS technique can be successfully extended to the study of ion/molecule reaction rates at significantly greater buffer gas pressures than previously considered feasible within the conventional view of the method.