The transition rate is calculated for picking up a single-valence or free electron in a solid into the $1s$ and $2s$ hydrogenic states on a completely stripped ion of charge $Z$ as the ion passes through a thin solid film in a given crystallographic direction between rows of atoms of charge $Z^{\prime }$. The results exhibit a structure reminiscent of the Okorokov effect, which is explainable in terms of a lattice momentum transfer-dependent phase space. The possibility of directionally or energetically tuning maxima in the pickup fraction or detuning competing processes is suggested. Possible uses are indicated for a beam of (possibly polarized) high-$Z$ metastables produced in this way in interesting experiments in atomic and weak-interaction physics.

• Received 17 September 1979

DOI:https://doi.org/10.1103/PhysRevB.22.88