Charge-state-dependent energy loss of slow ions. I. Experimental results on the transmission of highly charged ions

We report on energy loss measurements of slow $\left(v\ll v_0\right)$, highly charged $\left(Q>10\right)$ ions upon transmission through a 1-nm-thick carbon nanomembrane. We emphasize here the scaling of the energy loss with the velocity and charge exchange or loss. We show that a weak linear velocity dependence exists, whereas charge exchange dominates the kinetic energy loss, especially in the case of a large charge capture. A universal scaling of the energy loss with the charge exchange and velocity is found and discussed in this paper. A model for charge-state-dependent energy loss for slow ions is presented in paper II in this series [R. A. Wilhelm and W. Möller, Phys. Rev. A 93, 052709 (2016)].

Figure 1

Sketch of the ion beam passing through the sample holder into the electrostatic analyzer. The analyzer can be rotated around the sample.

Figure 2

Exit charge-state spectrum of ${\mathrm{Xe}}^{28+}$ ions at $E_{\mathrm{kin}}=126$ keV transmitted through a 1-nm-thick carbon nanomembrane. The spectrum is bimodal.

Figure 3

Energy loss of ${\mathrm{Xe}}^{20+}$ transmitted through a 1-nm-thick carbon nanomembrane as a function of the ion velocity for different observed charge exchanges (exit charge states). For a large charge exchange and a velocity around $2\times {10}^5$ m/s the energy loss increases with the velocity, whereas it becomes independent of the velocity for a smaller charge exchange. For a higher velocity, about $3.6\times {10}^5$ m/s, the energy loss decreases.

Figure 4

Energy loss as a function of exit charge state for different ion velocities $v$ and $Q_{\mathrm{in}}=20$. The target material is again a 1-nm-thick carbon nanomembrane. The data are fitted by a function $\alpha e^{\beta (Q_{\mathrm{in}}-Q_{\mathrm{exit}})/Q_{\mathrm{in}}}$ (see text).

Figure 5

Energy loss of Xe ions transmitted through a 1-nm-thick carbon nanomembrane as a function of the incident charge state for different charge exchanges (exit charge states). The primary kinetic energy is fixed to 40 keV. All energy loss data were fitted with the function $\mathrm{\Delta }E=\alpha +\beta Q_{\mathrm{in}}{e}^{\gamma (Q_{\mathrm{in}}-Q_{\mathrm{exit}})/Q_{\mathrm{in}}}$ (see text). To compare with the $Q_{\mathrm{exit}}=2$ data, a quadratic fit is shown as suggested recently in [22].

Figure 6

Energy loss as a function of relative charge loss $\mathrm{\Delta }Q/Q_{\mathrm{in}}$ for different incident charge states of Xe and also different incident kinetic energies of $E_{\mathrm{kin}}=4400\mathrm{eV}\times Q_{\mathrm{in}}$. The energy loss was rescaled by a factor $Q_{\mathrm{in}}^{-1}$ (see text), whereas now all energy losses follow a single-exponential function. Negative values are a result of the limited measurement accuracy.