Search for Wake-Bound Electron States

We have compared the electron velocity distributions observed at 180° when helium ions of 0.8-2 MeV are incident on both helium gas and carbon foils. These distributions are characteristic of electron loss from the atomic $1s$ state of the ion and not from a wake-bound state even for the case when a ${}_{}{}^3{}_{}{}^{}\mathrm{He}_{}^{++}{}_{}{}^{}$ ion first captures an electron from the solid and subsequently ejects it when inside the solid.