Ion Loss by Double Ionisation

Abstract

In our experiment a trapped $\mathrm {^{88}Sr^+}$ ion is lost by double ionisation after typically several hundred excitations to a Rydberg state. Similarly double ionisation occurs in ${\sim }{}{0.3}{}\mathrm {\%}$ excitations to a Rydberg state in the Mainz experiment [1]. Double ionisation thus presents an obstacle in trapped Rydberg ion experiments, discussed in Sect. 5.1. We know the ion is lost by double ionisation by measuring the final product to be $\mathrm {^{88}Sr^{2+}}$, these measurements are described in Sect. 5.2. We suspect Rydberg states with higher principal quantum numbers are more prone to double ionisation loss and that blackbody radiation increases the likelihood of double ionisation, though we have yet to carry out a systematic investigation of the effects of different parameters on the ion loss rate. Müller et al.  [2] briefly discuss double ionisation driven by the electric fields of the trap.