MASS DEPENDENT ION COLLECTION EFFICIENCIES IN A MASS SPECTROMETER1

For calculation of gaseous ion-molecule reaction cross sections from mass spectrometer data, the collection efficiencies for the primary and secondary ions must be known. A method for determining the discrimination among ions of different m/e is given in which the ratio of the analyzed ion current to the total saturation current is compared for various m/e values. Data were collected for H/sub 2/, D/sub 2/, CH/sub 4/, CD/sub 4/, Ne, C/sub 2/H/sub 2/, H/sub 2/S, Ar, Kr, and Xe gases and no rmalized to unity for xenon. There is little discrimination for any repeller field except for a small increase at low m/e. (D.L.C.)