Simultaneous measurement of the average ion-induced electron emission yield and the mean charge for isotachic ions in carbon foils

Knowledge of the incident ion's atomic number (${\mathrm{Z}}_1$) dependence of ion-induced electron emission yields can be the basis for a general understanding of ion-atom interaction phenomena and, in particular, for the design of ${\mathrm{Z}}_1$-sensitive detectors that could be useful, for example, in the separation of isobars in accelerator mass spectrometry. The ${\mathrm{Z}}_1$ dependence of ion-induced electron emission yields, γ, has been investigated using heavy ions ${\mathrm{C}}^{3+}$, ${\mathrm{O}}^{3+}$, ${\mathrm{F}}^{+3\mathrm{}}$, ${\mathrm{Na}}^{3+}$, ${\mathrm{Al}}^{3+}$, ${\mathrm{Si}}^{3+}$, ${\mathrm{P}}^{3+}$, ${\mathrm{S}}^{3+}$, ${\mathrm{Cl}}^{3+}$, ${\mathrm{K}}^{3+}$, ${\mathrm{Ti}}^{3+}$, ${\mathrm{Cr}}^{3+}$, ${\mathrm{Mn}}^{4+}$, ${\mathrm{Fe}}^{4+}$, ${\mathrm{Co}}^{4+}$, ${\mathrm{Ni}}^{4+}$, ${\mathrm{Cu}}^{4+}$, ${\mathrm{Ga}}^{4+}$, ${\mathrm{As}}^{5+}$, ${\mathrm{Br}}^{5+}$, ${\mathrm{Ru}}^{7+}$, ${\mathrm{Ag}}^{7+}$, ${\mathrm{Sn}}^{7+}$, and ${\mathrm{I}}^{8+}$ of identical velocity (v=${2\mathrm{v}}_0$, where ${\mathrm{v}}_0$ is the Bohr velocity) normally incident on 50 μg/${\mathrm{cm}}^2$ sputter-cleaned carbon foils. Measured yields as a function of ${\mathrm{Z}}_1$ reveal an oscillatory behavior with pronounced maxima and minima. Contrary to previously reported yields that assumed a monotonically increasing empirical mean charge state for the exiting ion, the present work indicates the ${\mathrm{Z}}_1$ oscillations in the experimentally measured yields, a fact masked in previous work. The strong ${\mathrm{Z}}_1$ oscillations can only be observed by simultaneous measurement of the yield and the mean charge state.