Experimental evidence for dielectronic excitation producing Ne K vacancies in 35-keV N7++Ne collisions

Young-type experiment using a single-electron source and an independent atomic-size two-center interferometer

Evidence is given for Young-type interferences caused by a single electron acting on a given double-center scatterer analogous to an atomic-size double-slit system. The electron is provided by autoionization of a doubly excited He atom following the capture of the electrons of H2 by a He2+ incoming ion. The autoionizing projectile is a single-electron source, independent of the interferometer provided by the two H+ centers of the fully ionized H2 molecule. This experiment resembles the famous thought experiment imagined by Feynman in 1963, in which the quantum nature of the electron is illustrated from a Young-like double-slit experiment. Well-defined oscillations are visible in the angular distribution of the scattered electrons, showing that each electron interferes with itself.

Unexpected x-ray emission due to formation of bound doubly excited states

A strong emission of characteristic M x rays is observed, without an M vacancy initially present, when slow highly charged ions (Ta(q+), q = 39--48) capture a single electron in single collisions with rare gas atoms (He). This is explained by the formation of bound doubly excited states through electron correlation. An elaborate theoretical treatment shows that bound doubly excited states are mixed with states where a Rydberg electron is bound in the core of a highly charged ion. It is striking that this occurs with a large probability (close to unity), and one needs to assume that higher Rydberg states are populated than predicted by the overbarrier model in order to explain the experimental results.