Internal dielectronic excitation in highly charged ions colliding with surfaces

Internal dielectronic excitation (IDE) is a correlated atomic physics process that takes place when the deexcitation of a Rydberg electron is accompanied by the excitation of a more tightly bound electron, resulting in a doubly excited inner-shell configuration. Subsequent x-ray emission involving an electron transition to a shell that initially contained no vacancies identifies the IDE process. IDE is mediated by the electron-electron interaction in a manner similar to a time-reversed Auger transition, and can occur during the neutralization of a slow highly charged ion interacting with a solid where there are many Rydberg levels that can give rise to correlated transitions to degenerate energy states. We have investigated IDE for a wide range of projectiles and solid targets by measuring the resulting x-ray emission. The characteristic features of the x-ray spectra suggest that IDE occurs above the surface of the solid.