A new single-stage mass spectrometric method for studying charge transfer reactions

Abstract

A method using a conventional retarding potential difference ion source in a new way to study charge transfer reactions is described. Potentials on five focus plates between the filament and ion box are applied so as to accelerate electrons, produce positive ions, decelerate the electrons and accelerate the positive ion beam. Only the primary positive ion beam traverses the ion box and is collected on the trap. This primary ion beam has momentum perpendicular to the mass analysis slit and is not collected. If charge transfer from the primary ions to a gas in the ion box occurs, the secondary ions are collected through the analysis slit with high efficiency. This method has features in common with the Cermak—Herman mode of ion source operation but also provides measurement of the primary ion beam. Thus dissociative charge transfer and total charge transfer between different molecules can be measured. Results compre favorably with those obtained by tandem mass spectrometers.