Variance of ion-electron coefficients with atomic number of impacting ions

Abstract

The relation between ion-electron coefficients γ and atomic number Z 1 of impacting ions on the electron multiplier of a mass spectrometer was investigated. Ions of 22 elements ranging from Li to Pb were measured on three dynode materials (CuBe, Al and Ni) for an ion energy of 8.0 keV. These results were extrapolated to ion-electron coefficients for constant ion velocity. The ion-electron coefficients obtained for constant ion velocity were combined with results given by Lao et al. [2] to form a set of 44 coefficients for the CuBe dynode. A periodic increase of γ( Z 1) at constant velocity was found for the dynode materials used. The trend of this increase agrees well with theory. Maxima in γ( Z 1) appeared for the noble gases and for group IVb, minima for groups IIa and IIb. The dynode material influenced the amplitude of the oscillations in γ( Z 1), but did not affect the location of maxima and minima in γ( Z 1). The comparison of the results obtained for γ( Z 1) showed good agreement with the periodicity found for electronic stopping.